Intussusception - Adult

Quick Answer

Adult intussusception is a rare cause of intestinal obstruction (5% of cases) characterized by telescoping of one bowel segment into another. Unlike paediatric intussusception, adult cases have an identifiable lead point in 70-90% (malignancy in 40-65% overall, 60% of colonic cases). CT abdomen/pelvis with IV contrast is the gold standard diagnostic tool (sensitivity 58-100%, specificity 57-100%). Management is almost always surgical resection without reduction due to high malignancy risk. Prognosis depends on underlying pathology, with mortality below 5% for benign causes but significantly higher for malignant disease.

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ACEM Exam Focus

What Examiners Expect

Fellowship Written SAQ:

• Differentiate adult from paediatric intussusception (lead point prevalence, reduction contraindications)
• Recognize CT imaging features (target sign, bowel-within-bowel)
• Understand classification (enteroenteric, ileocolic, colocolic) and malignancy risk stratification
• Know surgical principles (resection without reduction, oncologic considerations)

Fellowship OSCE:

• Systematic assessment of acute abdomen
• Interpretation of CT imaging showing intussusception
• Communication of malignancy risk and need for surgery
• Handover to surgical team with key information

Key Pitfall:

• Do NOT attempt hydrostatic or pneumatic reduction in adults (paediatric technique) - risk of perforation, tumour dissemination, and venous embolization

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Key Points

1. Adult intussusception is rare (5% of intestinal obstructions, 2-3 cases per million adults/year) and has a lead point in 70-90% cases (vs 10% in paediatrics)

2. Malignancy is common: 40-65% of adult intussusception has malignant lead point (60% in colonic, 30% in small bowel)

3. CT abdomen/pelvis with IV contrast is diagnostic gold standard: "target sign" (axial), "bowel-within-bowel" (coronal), mesenteric fat stranding, lymphadenopathy

4. Surgical resection without reduction is standard management (70-90% require surgery) to avoid tumour dissemination and enable oncologic resection margins

5. Classification by location determines malignancy risk: Enteroenteric (30% malignant) < Ileocolic/ileocaecal (40-50% malignant) < Colocolic (60-70% malignant)

6. Postoperative intussusception (post-gastric bypass, post-laparoscopic surgery) is a distinct entity: usually transient, may resolve with conservative management

7. Transient small bowel intussusception on CT (2-9% of abdominal CT scans) is often asymptomatic and resolves spontaneously - manage conservatively with interval imaging

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Epidemiology

Incidence and Demographics

Australian and New Zealand Context

• Incidence estimates: Approximately 50-75 cases per year in Australia, 10-15 cases per year in New Zealand (based on population extrapolation)
• Māori and Pacific Islander populations: Higher rates of colorectal cancer (1.5-2x European populations) may increase colocolic intussusception incidence [PMID: 25929355]
• Aboriginal and Torres Strait Islander populations: Lower colorectal cancer incidence but higher rates of gastric cancer and infectious enteritis that may predispose to intussusception [PMID: 28691157]
• Remote/rural presentations: Often delayed diagnosis due to limited access to CT imaging and surgical services

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Pathophysiology

Mechanism of Intussusception

Intussusception is the telescoping (invagination) of a proximal bowel segment (intussusceptum) into the lumen of an adjacent distal segment (intussuscipiens).

Anatomical Components

        Proximal bowel
              |
              v
    +---------+---------+
    |   INTUSSUSCEPTUM  |  <-- Inner telescoping segment
    |    (proximal)     |      (apex = leading point)
    +---------+---------+
              |
              v
    +-------------------+
    |  INTUSSUSCIPIENS  |  <-- Outer receiving segment
    |    (distal)       |      (distal to lead point)
    +-------------------+

Pathophysiological Consequences

Phase 1: Mechanical Obstruction (Hours 0-12)

• Luminal narrowing → partial or complete bowel obstruction
• Proximal bowel dilatation with fluid and gas accumulation
• Increased intraluminal pressure → nausea, vomiting, colicky pain

Phase 2: Vascular Compromise (Hours 12-24)

• Mesenteric vessels dragged into intussusceptum → venous congestion
• Lymphatic obstruction → bowel wall oedema
• Continued arterial inflow but impaired venous outflow → haemorrhagic infarction

Phase 3: Ischaemia and Necrosis (Hours 24-48+)

• Arterial insufficiency → transmural ischaemia
• Mucosal sloughing → "currant jelly" bloody mucoid stool (less common in adults than children)
• Bacterial translocation → sepsis, peritonitis
• Perforation risk (10-20% if delayed greater than 48 hours)

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Lead Points in Adult Intussusception

Critical Concept: Unlike paediatric intussusception (90% idiopathic, likely viral hypertrophied Peyer's patches), adult intussusception has an identifiable lead point in 70-90% of cases [PMID: 9250627, PMID: 19727960].

Classification by Location and Malignancy Risk

Benign Lead Points (30-60% of adult intussusception)

Inflammatory/Infectious:

• Meckel's diverticulum (most common cause in patients below 25 years) [PMID: 18641662]
• Appendiceal stump or appendicitis
• Crohn's disease strictures or inflammatory masses [PMID: 21475384]
• Intestinal tuberculosis (consider in endemic regions, Indigenous populations)
• Post-operative adhesions

Benign Neoplasms:

• Lipomas (most common benign lead point, 25-30% of benign cases) - characteristic fat density on CT [PMID: 20473593]
• Adenomatous polyps (especially greater than 2 cm)
• Hamartomatous polyps (Peutz-Jeghers syndrome)
• Inflammatory fibroid polyps (Vanek tumours)
• Gastrointestinal stromal tumour (GIST) - small, benign variants

Other:

• Endometriosis implants (ileocaecal region in women) [PMID: 19358878]
• Enteric duplication cysts

Malignant Lead Points (40-65% of adult intussusception)

Primary GI Malignancies:

• Adenocarcinoma (most common malignant lead point overall, 50% of malignant cases)
  • Small bowel adenocarcinoma (rare but highly associated with intussusception)
  • Colorectal adenocarcinoma (especially caecal)
• Lymphoma (20-30% of malignant lead points) [PMID: 16568331]
  • Non-Hodgkin lymphoma (MALT, diffuse large B-cell)
  • Particularly in HIV/AIDS patients, post-transplant
• Gastrointestinal stromal tumour (GIST) - larger, malignant variants (5-10%)
• Carcinoid tumours (ileum most common site)

Metastatic Disease:

• Melanoma metastases (common to small bowel) [PMID: 22198776]
• Lung cancer metastases
• Breast cancer metastases
• Renal cell carcinoma metastases

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Postoperative Intussusception

Distinct Entity: Postoperative intussusception is a recognized complication of abdominal and pelvic surgery, with different pathophysiology and management approach.

Incidence: 0.08-0.1% of laparoscopic procedures, 0.1-0.3% post-gastric bypass surgery [PMID: 18584272]

Mechanism:

• Altered bowel motility (post-surgical ileus recovery → abnormal peristalsis)
• Adhesions creating lead points
• Altered anatomy (Roux-en-Y gastric bypass → jejunojejunal intussusception at anastomosis)
• Long mesenteric limbs with increased mobility

Timing: Usually 1-4 weeks post-surgery (range 3 days to 2 years)

Management Approach:

• Often transient and self-limiting
• Conservative management with bowel rest, NGT decompression, IV fluids in stable patients
• Serial imaging (CT or ultrasound) to confirm resolution
• Surgical intervention if persistent greater than 48 hours, peritonitis, or bowel obstruction

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Clinical Presentation

Symptoms

Adult intussusception presents with non-specific symptoms that overlap with many causes of acute abdomen. Diagnosis is challenging and often delayed.

Classic Triad (Present in below 20% of Adult Cases)

Paediatric "Classic Triad" (rare in adults):

1. Colicky abdominal pain
2. Palpable abdominal mass
3. "Currant jelly" stool (bloody mucoid)

Reality in Adults:

• Triad present in only 10-20% of cases [PMID: 19727960]
• Symptoms often chronic and intermittent (weeks to months)
• May mimic irritable bowel syndrome, partial obstruction, or inflammatory bowel disease

Common Presentations

Acute vs Chronic Presentations

Acute Presentation (below 48 hours):

• Sudden onset severe colicky pain
• Vomiting (often bilious)
• Abdominal distension
• Signs of intestinal obstruction
• Peritonitis if ischaemia/perforation

Chronic/Intermittent Presentation (weeks to months):

• Recurrent episodes of crampy abdominal pain
• Partial obstruction symptoms
• Weight loss, anorexia
• Intermittent nausea
• Often misdiagnosed as IBS, IBD, or functional disorder
• High index of suspicion needed - leads to delayed diagnosis in 30-50% [PMID: 15780339]

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Physical Examination

General Appearance

• Acute presentation: Distressed, restless, dehydrated
• Chronic presentation: Often well-appearing between episodes

Vital Signs

Abdominal Examination

Inspection:

• Distension (proximal bowel dilatation)
• Visible peristalsis (rare, suggests chronic partial obstruction)
• Surgical scars (postoperative intussusception)

Palpation:

• "Sausage-shaped" mass (10-40% of cases) - classically in right lower quadrant (ileocolic)
  • Mobile, smooth, elongated
  • Tender to palpation
  • May be palpable on bimanual examination (rectal + abdominal)
• Dance's sign (empty right lower quadrant due to migration of caecum) - rare in adults
• Guarding, rigidity, rebound tenderness → peritonitis (ischaemia, perforation)

Percussion:

• Tympanic (gaseous distension)
• Loss of liver dullness (perforation with pneumoperitoneum)

Auscultation:

• Hyperactive "tinkling" bowel sounds (early obstruction)
• High-pitched rushes (partial obstruction)
• Absent bowel sounds (late obstruction, peritonitis)

Rectal Examination:

• Mandatory in all cases of suspected intussusception
• May palpate intussusceptum (especially ileocolic extending into rectum)
• Bright red blood or "currant jelly" stool on glove (10-20%)
• Occult blood (40-60%)

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Investigations

Laboratory Studies

Initial Blood Tests

Additional Studies (If Suspicion of Malignancy)

• CEA (carcinoembryonic antigen) - elevated in colorectal adenocarcinoma (greater than 5 μg/L)
• CA 19-9 - elevated in pancreatic/biliary/gastric malignancy
• LDH - markedly elevated in lymphoma (greater than 500 U/L)

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Imaging

CT Abdomen/Pelvis with IV Contrast - GOLD STANDARD

Indication: All adult patients with suspected intussusception [PMID: 23528844]

Diagnostic Performance:

• Sensitivity: 58-100% (higher for symptomatic cases)
• Specificity: 57-100%
• Accuracy: 85-100% for detecting intussusception [PMID: 23528844, PMID: 17522084]

Protocol:

• Oral contrast NOT required (may delay diagnosis)
• IV contrast ESSENTIAL for assessing bowel perfusion, lead point characterization
• Portal venous phase (60-70 seconds post-contrast)
• Multiplanar reconstruction (coronal, sagittal)

CT Imaging Features

Pathognomonic Signs:

1. "Target Sign" or "Doughnut Sign" (Axial Views)

   • Concentric rings of alternating density
   • Outer ring = intussuscipiens (dilated bowel)
   • Inner ring = intussusceptum (telescoped bowel)
   • Central area = invaginated mesentery and vessels
   • Diameter typically greater than 3 cm (range 2-5 cm)

2. "Bowel-Within-Bowel" or "Sausage Sign" (Coronal Views)

   • Elongated mass showing invaginated bowel
   • Length typically 5-10 cm (range 3-30 cm)
   • Inner bowel wall visible within outer bowel lumen

3. Mesenteric Fat and Vessels

   • "Reniform" or "kidney-shaped" mass (mesenteric fat dragged into intussuscipiens)
   • Mesenteric vessels stretched and pulled into lumen
   • Vascular engorgement

Secondary Features:

Lead Point Characterization:

Transient Small Bowel Intussusception

Incidental CT Finding: 2-9% of abdominal CT scans show small bowel intussusception [PMID: 10588935, PMID: 16985557]

Characteristics:

• Usually below 3 cm diameter, below 3 cm length
• No lead point identified
• No proximal bowel obstruction
• Patient asymptomatic or minimal symptoms

Pathophysiology:

• Likely represents normal variant of peristalsis
• May be triggered by viral enteritis, hypermotility states

Management:

• Conservative management with observation
• Repeat imaging in 1-2 weeks if persistent symptoms
• Surgical referral if persistent on repeat imaging OR symptoms progress
• Spontaneous resolution in 80-90% [PMID: 16985557]

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Ultrasound - Limited Role in Adults

Diagnostic Performance:

• Sensitivity 80-100% in experienced hands (operator-dependent)
• Specificity 85-100%
• Limited by bowel gas, obesity, patient discomfort

Ultrasound Findings:

• "Target sign" (axial) - concentric rings
• "Pseudokidney sign" (longitudinal) - hypoechoic rim (oedematous bowel wall) surrounding hyperechoic centre (mucosa)
• Reduced or absent peristalsis
• Free fluid

Utility:

• May be useful in postoperative patients with high clinical suspicion (less bowel gas)
• NOT recommended as first-line in adults (CT superior) [PMID: 23528844]
• More useful in paediatric population

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Plain Abdominal Radiography (AXR) - Low Sensitivity

Findings:

• Non-specific signs of bowel obstruction:
  • Dilated small bowel loops (greater than 3 cm)
  • Air-fluid levels
  • Paucity of gas in colon
• Soft tissue mass (rare, only 25% of cases) [PMID: 9250627]
• "Coiled spring" or "stacked coins" appearance (rare)
• Free air under diaphragm (perforation)

Role:

• NOT recommended for diagnosis of intussusception (sensitivity below 50%)
• May be performed as initial investigation for acute abdomen
• If AXR shows obstruction → proceed directly to CT abdomen/pelvis

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MRI Abdomen - Emerging Role

Indications:

• Pregnant patients (avoid ionizing radiation)
• Young patients requiring repeat imaging
• Equivocal CT findings

MRI Findings:

• Similar to CT: target sign, bowel-within-bowel
• T2-weighted images show oedematous bowel wall (hyperintense)
• Gadolinium contrast assesses bowel perfusion

Limitations:

• Limited availability in emergency setting
• Longer acquisition time (patient must lie still)
• Higher cost

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Diagnosis

Diagnostic Criteria

Clinical Diagnosis of Adult Intussusception:

1. Imaging confirmation (CT, ultrasound, or MRI) showing classic signs:

   • Target/doughnut sign (axial)
   • Bowel-within-bowel appearance (coronal)
   • Mesenteric fat/vessels within intussuscipiens

2. Clinical symptoms consistent with bowel obstruction or abdominal mass

3. Classification by location:

   • Enteroenteric (small bowel-small bowel)
   • Ileocolic/ileocaecal
   • Colocolic (large bowel-large bowel)
   • Retrograde (rare)

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Differential Diagnosis

Bowel Obstruction

Abdominal Mass

Other Causes of Abdominal Pain

• Gastroenteritis - usually diarrhoea predominant, no mass
• Irritable bowel syndrome - chronic intermittent symptoms, normal imaging
• Mesenteric ischaemia - older patients, atrial fibrillation, out-of-proportion pain
• Pancreatitis - elevated lipase, peripancreatic inflammation on CT

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Management

Initial Resuscitation (ABCDE Approach)

Airway and Breathing

• Secure airway if vomiting and reduced GCS (aspiration risk)
• High-flow oxygen 15 L/min via non-rebreather mask
• Target SpO₂ greater than 94%

Circulation

• Large-bore IV access (2× 16-18G cannulae)
• IV fluid resuscitation:
  • Hartmann's solution or 0.9% NaCl 20 mL/kg bolus (e.g., 1-2 L in 70 kg adult)
  • Reassess after each bolus (HR, BP, urine output, lactate)
  • Target MAP greater than 65 mmHg, urine output greater than 0.5 mL/kg/h
• Commence vasopressors (noradrenaline) if hypotension persists despite 40 mL/kg fluid

Disability

• GCS assessment
• Blood glucose measurement (exclude hypoglycaemia)

Exposure

• Comprehensive abdominal examination
• Look for hernias, surgical scars

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Analgesia and Antiemetics

Analgesia:

• Opioids for moderate-severe pain:
  • Morphine 2.5-5 mg IV/SC every 5-10 minutes, titrate to effect
  • Oxycodone 5-10 mg PO (if tolerating oral)
  • Fentanyl 25-50 mcg IV (elderly, renal impairment)
• Paracetamol 1 g IV/PO QID (adjunct)

Antiemetics:

• Metoclopramide 10 mg IV (caution if complete obstruction - may worsen)
• Ondansetron 4-8 mg IV (preferred if complete obstruction)

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Nasogastric Decompression

Indication:

• Vomiting (especially bilious)
• Bowel obstruction with proximal dilatation
• Pre-operative preparation

Technique:

• Insert nasogastric tube (NGT), confirm position (aspiration of gastric contents, pH below 5.5)
• Free drainage or low intermittent suction
• Monitor and replace losses (IV fluid replacement)

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Antibiotics

Indication: Suspected bowel ischaemia, perforation, or sepsis

Empiric Regimen (Broad-Spectrum):

Duration:

• Continue until source control (surgery)
• Post-operative course as per surgical team

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Surgical Management - DEFINITIVE TREATMENT

Principle: Adult intussusception requires surgical resection in 70-90% of cases [PMID: 19727960, PMID: 15780339].

Surgical Indications (Absolute)

1. All colocolic and ileocolic intussusception (high malignancy risk 40-70%)
2. Enteroenteric intussusception with:
   • Lead point identified on imaging (mass, polyp)
   • Bowel ischaemia or perforation
   • Complete bowel obstruction
   • Symptoms greater than 48 hours duration
3. Peritonitis (ischaemia, perforation)
4. Haemodynamic instability despite resuscitation

Surgical Approach

Laparotomy vs Laparoscopy:

• Laparotomy (open) - traditional approach, allows better oncologic resection, easier management of ischaemic bowel
• Laparoscopy - feasible in selected cases (transient small bowel intussusception without mass, postoperative intussusception), may convert to open if malignancy or difficult anatomy

Reduction vs Resection Without Reduction:

Exception: Reduction may be considered if:

• Transient small bowel intussusception, no lead point on imaging
• Postoperative intussusception (benign aetiology)
• Young patient, short segment, no ischaemia

Oncologic Principles for Malignant Lead Points:

• Formal segmental resection with adequate margins (5-10 cm proximal and distal)
• Lymphadenectomy (regional lymph node dissection)
• Right hemicolectomy for caecal/ascending colon tumours
• En bloc resection of involved structures (if locally advanced)
• No bowel manipulation before vascular ligation (prevent tumour cell dissemination)

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Specific Surgical Procedures by Location

Small Bowel (Enteroenteric) Intussusception:

• Segmental small bowel resection with primary anastomosis
• Margins 5-10 cm from intussusception apex
• Inspect entire small bowel for synchronous lesions (especially if lymphoma, metastases)

Ileocolic Intussusception:

• Right hemicolectomy (if lead point in caecum or ascending colon)
• Ileocaecal resection (if benign lead point and short segment)

Colocolic Intussusception:

• Formal oncologic colectomy (right/left hemicolectomy, sigmoid colectomy)
• High ligation of vascular pedicle and lymphadenectomy
• May require Hartmann's procedure if perforation, peritoneal contamination

Postoperative Intussusception:

• Often spontaneously reduces during laparoscopy/laparotomy
• If persists: reduction alone may be adequate (no lead point)
• Consider plication of bowel to prevent recurrence

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Conservative (Non-Operative) Management - SELECTED CASES ONLY

Indications (All Must Be Met):

1. Transient small bowel intussusception on CT (incidental finding, below 3 cm diameter)
2. No lead point identified on imaging
3. No bowel obstruction (no proximal dilatation)
4. Asymptomatic or minimal symptoms
5. Postoperative intussusception (if stable, no peritonitis)

Conservative Management Protocol:

• Bowel rest (NBM initially, advance diet as tolerated)
• IV fluid hydration
• Analgesia as needed
• Serial clinical assessment (abdominal examination, vital signs)
• Repeat imaging (CT or ultrasound) in 24-48 hours to confirm resolution
• Low threshold for surgical consultation if symptoms worsen

Success Rate: 80-90% resolution in transient small bowel intussusception [PMID: 16985557]

Failure of Conservative Management:

• Persistent symptoms greater than 48 hours
• Development of peritonitis, bowel obstruction
• Persistent intussusception on repeat imaging
• → Surgical resection required

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Reduction Techniques (Paediatric - NOT for Adults)

Hydrostatic (Barium/Water-Soluble Contrast) Reduction:

• CONTRAINDICATED in adults due to:
  • High malignancy risk (40-65%)
  • Risk of perforation and tumour dissemination
  • Risk of venous tumour embolization
  • Low success rate (below 20% in adults vs 70-90% in children)

Pneumatic (Air) Reduction:

• CONTRAINDICATED in adults for same reasons

Key ACEM Pitfall:

• Do NOT attempt non-operative reduction (hydrostatic/pneumatic) in adult intussusception
• Paediatric management principles DO NOT apply to adults

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Disposition

Admission Criteria

All adult intussusception requires:

• Surgical consultation (general surgery)
• Hospital admission
  • Surgical ward (if planned for operative management)
  • High-dependency unit or ICU (if peritonitis, sepsis, haemodynamic instability)

ICU Admission Criteria

• Septic shock (vasopressors required)
• Respiratory failure (requiring intubation)
• Severe metabolic acidosis (pH below 7.2, lactate greater than 4 mmol/L)
• Multi-organ failure

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Referral and Handover

Surgical Referral Information:

1. Patient demographics and presenting complaint
2. Clinical findings:
   • Duration of symptoms
   • Abdominal examination (peritonitis? palpable mass?)
   • Vital signs and haemodynamic status
3. Investigations:
   • Lactate level (ischaemia marker)
   • CT imaging findings (location, lead point, ischaemia?)
4. Resuscitation performed:
   • IV fluid volume given
   • Vasopressors (if applicable)
   • NGT inserted?
   • Antibiotics given?
5. Current status and urgency:
   • Stable for theatre or immediate surgery required?

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Complications

Perioperative Complications

Long-Term Complications

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Prognosis

Overall Outcomes

Prognostic Factors

Good Prognosis:

• Benign lead point (lipoma, polyp)
• Early diagnosis (below 48 hours)
• No bowel ischaemia or perforation
• Small bowel (enteroenteric) location
• Successful segmental resection

Poor Prognosis:

• Malignant lead point (especially colorectal adenocarcinoma with metastases)
• Delayed diagnosis (greater than 48 hours, bowel necrosis)
• Perforation with peritonitis
• Colocolic intussusception (higher malignancy rate)
• Advanced age (greater than 70 years), comorbidities

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Pitfalls and Pearls

Key Pitfalls to Avoid

1. Assuming adult intussusception is idiopathic (like paediatrics)

   • 70-90% have lead point; 40-65% malignant
   • Always investigate for underlying pathology

2. Attempting hydrostatic or pneumatic reduction

   • Contraindicated in adults
   • Risk of perforation, tumour dissemination, venous embolization

3. Delaying CT imaging

   • Plain AXR has low sensitivity (below 50%)
   • CT is gold standard - perform early

4. Missing transient small bowel intussusception on incidental CT

   • 2-9% of abdominal CT scans
   • Usually benign, but requires clinical correlation and interval imaging if symptomatic

5. Underestimating ischaemia risk

   • Check lactate early and serially
   • Non-enhancing bowel on CT = ischaemia/necrosis → urgent surgery

6. Dismissing chronic intermittent symptoms

   • 30-50% have delayed diagnosis due to intermittent symptoms mimicking IBS/IBD
   • Consider intussusception in unexplained recurrent abdominal pain + weight loss

7. Inadequate oncologic resection

   • Formal segmental resection with lymphadenectomy required for malignant lead points
   • Do NOT perform simple reduction or local excision

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Clinical Pearls

1. Adult intussusception is a surgical disease

   • 70-90% require operative management
   • Early surgical consultation is key

2. CT abdomen/pelvis with IV contrast is diagnostic gold standard

   • Sensitivity 58-100%, specificity 57-100%
   • "Target sign" (axial), "bowel-within-bowel" (coronal)

3. Location predicts malignancy risk

   • Enteroenteric (30% malignant) < Ileocolic (40-50%) < Colocolic (60-70%)

4. Lactate is the best marker of bowel ischaemia

   • Lactate greater than 2 mmol/L suggests ischaemia
   • Lactate greater than 4 mmol/L indicates severe ischaemia → urgent surgery

5. Postoperative intussusception is a distinct entity

   • Usually transient, may resolve with conservative management
   • Common after gastric bypass, laparoscopic surgery

6. Transient small bowel intussusception is often benign

   • 2-9% of abdominal CT scans, 80-90% resolve spontaneously
   • Requires clinical correlation, interval imaging

7. Standard surgical approach is resection WITHOUT reduction

   • Prevents tumour dissemination
   • Allows oncologic resection margins
   • Facilitates histopathologic diagnosis

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Indigenous Health Considerations

Aboriginal and Torres Strait Islander Populations

Epidemiology:

• Lower incidence of colorectal cancer compared to non-Indigenous Australians, but diagnosed at younger age (median 60 vs 70 years) [PMID: 28691157]
• Higher rates of gastric cancer (2-3x) and infectious enteritis may predispose to benign lead points
• Delayed presentation common due to:
  • Geographic isolation (remote communities)
  • Limited access to CT imaging and surgical services
  • Distrust of healthcare system (historical trauma)
  • Cultural beliefs about illness

Management Considerations:

• Early retrieval planning: RFDS coordination for remote community patients requiring surgery
• Cultural safety:
  • Explain need for surgery and potential malignancy diagnosis with sensitivity
  • Involve Aboriginal Health Liaison Officers or Workers
  • Allow family presence during consultation
  • Understand "shame" concept (reluctance to discuss bowel symptoms)
• Communication:
  • Use interpreters if English not first language
  • Avoid medical jargon, use plain language
  • Visual aids helpful (drawings, diagrams)
• Post-operative care:
  • Consider discharge planning early (may need extended stay in regional centre if from remote area)
  • Arrange telehealth follow-up for remote patients
  • Coordinate with local clinic for post-op wound care

Remote/Rural ED Considerations:

• Limited access to CT imaging (may require transfer to regional centre for imaging)
• Ultrasound may be initial imaging if CT unavailable, but low threshold for transfer if suspicious
• Early consultation with retrieval services (RFDS, state retrieval service)
• Stabilize before transfer: IV fluids, analgesia, antibiotics, NGT decompression

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Māori and Pacific Islander Populations (New Zealand)

Epidemiology:

• Māori and Pacific Islander populations have higher incidence of colorectal cancer (1.5-2x European) and younger age at diagnosis [PMID: 25929355]
• Colocolic intussusception more common → higher malignancy risk
• Barriers to healthcare access:
  • Socioeconomic factors
  • Rural/remote residence (especially in Northland, East Cape, Hawke's Bay)
  • Cultural factors (whānau decision-making, distrust of Pākehā healthcare)

Management Considerations:

• Whānau (family) involvement:
  • Include family in decision-making (collective vs individualistic approach)
  • Allow whānau presence during procedures (if feasible)
• Cultural protocols (tikanga):
  • Karakia (prayers) before/after procedures
  • Understand tapu and noa concepts (sacredness, restriction, cleansing)
  • Respect for the body (reluctance for autopsy if patient dies)
• Māori health models:
  • "Te Whare Tapa Whā (four cornerstones: taha tinana [physical], taha wairua [spiritual], taha whānau [family], taha hinengaro [mental/emotional])"
  • Address all four dimensions, not just physical illness
• Communication:
  • Use Te Reo Māori interpreters if needed
  • Engage Māori health navigators
  • Explain surgery and malignancy risk with cultural sensitivity

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Remote and Rural Emergency Medicine

Challenges in Remote/Rural EDs

1. Limited diagnostic imaging:

   • No CT scanner in many rural hospitals
   • Ultrasound may be only available imaging
   • Plain AXR low sensitivity for intussusception

2. Limited surgical services:

   • No general surgery on-site
   • Transfer required for operative management

3. Retrieval logistics:

   • RFDS (Australia) or rescue helicopter (New Zealand) coordination
   • Weather-dependent (may delay retrieval)
   • Long transfer times (hours)

4. Limited specialist support:

   • No on-site gastroenterology/oncology
   • Telehealth consultation may be available

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Management in Remote/Rural Setting

Initial Assessment and Stabilization:

1. ABCDE approach with IV fluid resuscitation
2. Analgesia (opioids as needed)
3. NGT decompression if vomiting
4. Antibiotics if suspected ischaemia/sepsis
5. Laboratory investigations (FBC, UEC, lactate, CRP)

Imaging:

• Ultrasound if available (may show target sign, but operator-dependent)
• Plain AXR to assess for bowel obstruction, perforation
• Low threshold for transfer to regional centre with CT for suspected intussusception

Retrieval Coordination:

• Early contact with RFDS or state retrieval service (e.g., NSW Ambulance Aeromedical, Queensland Retrieval Services)
• Provide clinical details: haemodynamic status, lactate, suspected diagnosis
• Stabilize patient before transfer:
  • IV access (2 large-bore)
  • Adequate analgesia
  • NGT inserted
  • Antibiotics commenced
• Receiving hospital: Ensure surgical team aware of incoming patient

Telehealth Consultation:

• Discuss case with general surgeon at regional centre
• Send images (AXR, ultrasound) via secure platform
• Confirm retrieval destination and urgency

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RFDS Protocols (Australia)

Patient Selection for Retrieval:

• All adult intussusception requiring CT imaging (if unavailable locally) or surgical management
• Priority 1 (immediate): Peritonitis, haemodynamic instability, lactate greater than 4 mmol/L
• Priority 2 (urgent, below 4 hours): Bowel obstruction, lactate 2-4 mmol/L, stable but requires surgery

Pre-Retrieval Checklist:

• IV access (2× large-bore)
• IV fluid resuscitation (target MAP greater than 65 mmHg)
• Analgesia (morphine, fentanyl)
• Antiemetics (ondansetron)
• NGT insertion (if vomiting)
• Antibiotics (if sepsis suspected)
• Blood tests sent (FBC, UEC, lactate, Group & Hold)
• Urine output monitoring (IDC if prolonged transfer)

Communication:

• Handover to RFDS medical team (doctor/paramedic)
• Provide written notes and medication chart
• Contact receiving hospital surgical team

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ACEM Exam Assessment Materials

Viva Practice Scenarios

Viva Scenario 1: Acute Ileocolic Intussusception with Surgical Emergency

Stem: "A 52-year-old woman presents to your ED with 24 hours of worsening right lower quadrant abdominal pain, nausea, and vomiting. She has a temperature of 38.2°C, HR 115 bpm, BP 95/60 mmHg. On examination, she has a tender, palpable sausage-shaped mass in the right iliac fossa with guarding. CT abdomen/pelvis shows ileocolic intussusception with a 3 cm soft tissue lead point and poor enhancement of the intussuscepted bowel wall."

Question 1: What are your immediate priorities in the ED?

Model Answer:

• ABCDE approach:
  • "Airway: Patent, no immediate concern"
  • "Breathing: Administer high-flow oxygen 15 L/min via NRBM, target SpO₂ greater than 94%"
  • "Circulation: Hypotensive (BP 95/60) → 2× large-bore IV access (16-18G), IV fluid resuscitation with Hartmann's/0.9% NaCl 20 mL/kg bolus (e.g., 1.5 L), reassess after each bolus. Consider vasopressors (noradrenaline) if hypotension persists despite 40 mL/kg fluid."
  • "Disability: GCS, blood glucose"
  • "Exposure: Complete abdominal examination, look for hernias"
• Analgesia: Morphine 2.5-5 mg IV titrated to effect
• NGT decompression: Insert NGT for vomiting, free drainage
• Antibiotics: Broad-spectrum (e.g., piperacillin-tazobactam 4.5 g IV) for suspected bowel ischaemia/sepsis
• Investigations: FBC, UEC, lactate (critical marker of ischaemia), CRP, Group & Hold
• Urgent surgical consultation: General surgery for operative management

Question 2: Interpret the CT findings. What is the significance of "poor enhancement of the intussuscepted bowel wall"?

Model Answer:

• CT findings:
  • Ileocolic intussusception with 3 cm soft tissue lead point → likely mass (polyp, tumour)
  • Poor enhancement of intussuscepted bowel wall → bowel ischaemia or necrosis
• Significance:
  • Bowel normally enhances with IV contrast (perfusion)
  • Decreased/absent enhancement indicates impaired arterial blood supply → ischaemia
  • Risk of transmural necrosis, perforation, sepsis
  • Urgent surgical indication - cannot be managed conservatively
• Expected additional CT features of ischaemia:
  • Bowel wall thickening greater than 3 mm
  • Mesenteric fat stranding
  • Free fluid (ascites)
  • Pneumatosis intestinalis (gas in bowel wall) - advanced ischaemia
  • Pneumoperitoneum (free air) - perforation

Question 3: What surgical approach is required? Why is hydrostatic reduction contraindicated in adults?

Model Answer:

• Surgical approach:
  • Resection WITHOUT reduction - standard of care in adults
  • Likely right hemicolectomy given ileocolic location and lead point (caecal tumour suspected)
  • Formal oncologic resection with adequate margins (5-10 cm), lymphadenectomy
  • No bowel manipulation before vascular ligation (prevent tumour cell dissemination)
• Why hydrostatic reduction is contraindicated:
  1. High malignancy risk (40-65% in adults; 60% in colonic intussusception) → reduction risks tumour cell dissemination and venous embolization
  2. Risk of perforation - ischaemic bowel is friable, manipulation may cause perforation
  3. Inadequate treatment - does not address underlying lead point, high recurrence risk
  4. Low success rate in adults (below 20% vs 70-90% in children)
• Exception: Reduction may be considered in transient small bowel intussusception without lead point or ischaemia (rare)

Question 4: What is the expected histopathology of the lead point? What is the prognosis?

Model Answer:

• Expected histopathology (ileocolic with 3 cm lead point):
  • Caecal adenocarcinoma (most likely) - 60% of colonic intussusception
  • "Alternatively: lymphoma, lipoma, polyp, GIST"
• Prognostic factors:
  • "Adenocarcinoma prognosis depends on stage:"
    • Stage I-II (localized): 5-year survival 70-90%
    • Stage III (lymph node involvement): 5-year survival 40-60%
    • Stage IV (metastatic): 5-year survival below 10%
  • Bowel ischaemia/necrosis increases perioperative morbidity (10-40%)
  • "Overall mortality for adult intussusception: 1-8.7% [PMID: 19727960]"
  • "Mortality for malignant lead point: 8-30% (depends on stage)"
• Follow-up:
  • Oncology referral for adjuvant chemotherapy (if stage II-III)
  • Surveillance colonoscopy

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Viva Scenario 2: Chronic Intermittent Symptoms (Missed Diagnosis)

Stem: "A 38-year-old man presents with 6 months of intermittent crampy periumbilical pain, nausea, and 5 kg weight loss. He has been seen in ED twice and diagnosed with 'gastroenteritis' and 'IBS'. Today, he presents with more severe pain and vomiting. CT abdomen/pelvis shows small bowel intussusception with a 1.5 cm lead point in the mid-ileum."

Question 1: Why was this diagnosis missed on previous presentations? What red flags should have prompted earlier imaging?

Model Answer:

• Why diagnosis missed:
  • Adult intussusception has non-specific symptoms that overlap with common GI conditions (gastroenteritis, IBS, IBD)
  • 30-50% of adult intussusception has delayed diagnosis due to chronic/intermittent presentation [PMID: 15780339]
  • Intermittent intussusception can spontaneously reduce between episodes → normal examination
  • Previous clinicians may have relied on clinical diagnosis without imaging (AXR or CT)
• Red flags that should have prompted imaging:
  1. Weight loss (5 kg in 6 months) - suggests organic pathology, not functional disorder
  2. Recurrent presentations - same symptoms over 6 months, multiple ED visits
  3. Nausea/vomiting - less typical for IBS
  4. Age below 50 years with unexplained weight loss - consider malignancy or inflammatory pathology
  5. Palpable abdominal mass (if present on examination)
• Learning point: High index of suspicion for organic pathology in recurrent abdominal pain + weight loss

Question 2: What are the differential diagnoses for a 1.5 cm lead point in the mid-ileum?

Model Answer: Benign (70% in enteroenteric intussusception):

• Meckel's diverticulum (especially age below 25 years)
• Lipoma (most common benign, 25-30%)
• Inflammatory fibroid polyp (Vanek tumour)
• Hamartomatous polyp (Peutz-Jeghers syndrome - check for perioral pigmentation)
• Crohn's disease (inflammatory mass/stricture)

Malignant (30% in enteroenteric intussusception):

• Small bowel adenocarcinoma (rare but associated with intussusception)
• Lymphoma (NHL, especially in HIV/immunosuppressed)
• GIST (1.5 cm may be benign or low malignant potential)
• Metastases (melanoma, breast, lung, renal cell - check for primary malignancy history)

Question 3: What surgical approach is required? Would you consider conservative management?

Model Answer:

• Surgical approach:
  • Segmental small bowel resection with primary anastomosis
  • Resection WITHOUT reduction (standard in adults, even for enteroenteric)
  • Margins 5-10 cm from apex of intussusception
  • Inspect entire small bowel intraoperatively for synchronous lesions (especially if lymphoma or metastases)
  • Send resection specimen for histopathology to identify lead point
• Conservative management:
  • "NOT recommended in this case because:"
    1. Identifiable lead point on imaging (1.5 cm mass)
    2. Symptomatic with vomiting
    3. 6 months of symptoms (not transient)
    4. Need histopathologic diagnosis to rule out malignancy
• Exception: Conservative management only if:
  • Transient small bowel intussusception (incidental CT finding, below 3 cm diameter, no lead point, asymptomatic)
  • 80-90% resolve spontaneously [PMID: 16985557]

Question 4: What is the prognosis? What follow-up is required?

Model Answer:

• Prognosis:
  • "If benign lead point (e.g., lipoma, Meckel's): Excellent prognosis after resection, recurrence below 5%"
  • "If malignant lead point (e.g., adenocarcinoma): Prognosis depends on stage (see Scenario 1)"
  • "Overall mortality below 5% for benign causes [PMID: 9250627]"
• Follow-up:
  • Histopathology review (2-3 days) to identify lead point
  • Outpatient surgical follow-up (2-4 weeks) - wound check, histopathology discussion
  • "If malignancy: Oncology referral for staging (CT chest/abdomen/pelvis, PET if lymphoma) and treatment plan (chemotherapy, surveillance)"
  • "If benign: Discharge from surgical care after wound healing"

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Viva Scenario 3: Transient Small Bowel Intussusception (Incidental Finding)

Stem: "A 45-year-old woman undergoes CT abdomen/pelvis for suspected appendicitis. The report states: 'Normal appendix. Incidental finding of small bowel intussusception in the left mid-abdomen, measuring 2.5 cm in diameter and 2 cm in length. No lead point identified. No proximal bowel dilatation. No free fluid.' She has no abdominal pain now, is well-appearing, and tolerating oral fluids."

Question 1: What is transient small bowel intussusception? How common is it?

Model Answer:

• Definition: Transient (or physiologic) small bowel intussusception is an incidental CT finding of small bowel invagination, usually asymptomatic and self-limiting
• Incidence: 2-9% of abdominal CT scans [PMID: 10588935, PMID: 16985557]
• Pathophysiology:
  • Likely represents normal variant of peristalsis - transient telescoping during normal bowel contractions
  • May be triggered by viral enteritis (hypermotility), hypermotility states
• Characteristics:
  • Usually below 3 cm diameter, below 3 cm length
  • No identifiable lead point
  • No proximal bowel obstruction (no dilated bowel)
  • Patient asymptomatic or minimal symptoms
• Natural history: 80-90% resolve spontaneously within days to weeks [PMID: 16985557]

Question 2: How do you differentiate transient intussusception from pathologic intussusception requiring surgery?

Model Answer:

Question 3: What is your management plan for this patient?

Model Answer:

• Disposition: Discharge home (well-appearing, asymptomatic, no lead point, no obstruction)
• Safety-netting advice:
  • "Return to ED if:"
    • Abdominal pain develops or worsens
    • Vomiting (especially bilious)
    • Inability to tolerate oral fluids
    • Bloody stools
  • GP follow-up in 1 week
• Interval imaging:
  • Repeat CT or ultrasound in 1-2 weeks to confirm resolution (if patient develops symptoms)
  • If asymptomatic, repeat imaging optional (may be omitted as 80-90% resolve spontaneously)
• Surgical referral:
  • NOT required if asymptomatic
  • Refer if persistent on repeat imaging OR symptoms develop

Question 4: When would you admit this patient or consult surgery?

Model Answer:

• Admit and consult surgery if:
  1. Symptoms develop (abdominal pain, vomiting, obstruction)
  2. Peritonitis on examination (guarding, rebound tenderness)
  3. Persistent intussusception on repeat imaging (after 1-2 weeks) with symptoms
  4. Lead point identified on CT (any size mass/polyp)
  5. Bowel obstruction on CT (proximal dilatation)
  6. Ischaemia signs on CT (poor enhancement, free fluid)
• In this case: None of the above criteria met → safe to discharge with safety-netting

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Viva Scenario 4: Postoperative Intussusception

Stem: "A 32-year-old woman presents to ED 10 days post-laparoscopic Roux-en-Y gastric bypass with intermittent colicky abdominal pain and nausea. CT abdomen/pelvis shows jejunojejunal intussusception at the jejunojejunostomy anastomosis, 4 cm in diameter. The patient is haemodynamically stable, abdomen soft with mild periumbilical tenderness, no peritonitis. Lactate 1.2 mmol/L."

Question 1: What is postoperative intussusception? Why does it occur after bariatric surgery?

Model Answer:

• Definition: Postoperative intussusception is a recognized complication of abdominal and pelvic surgery, particularly laparoscopic procedures
• Incidence:
  • 0.08-0.1% after laparoscopic procedures [PMID: 18584272]
  • 0.1-0.3% after Roux-en-Y gastric bypass
  • "Timing: usually 1-4 weeks post-surgery (range 3 days to 2 years)"
• Mechanisms:
  1. Altered bowel motility: Post-surgical ileus recovery → abnormal peristalsis → telescoping
  2. Anastomosis as lead point: Jejunojejunostomy creates "lead point" where bowel is fixed
  3. Long mesenteric limbs: Roux-en-Y creates long alimentary and biliopancreatic limbs with increased mobility
  4. Adhesions: Early adhesion formation may tether bowel, create lead point

Question 2: How does management differ from spontaneous (non-postoperative) intussusception?

Model Answer:

Question 3: What is your management plan for this stable patient?

Model Answer:

• Initial conservative management (Trial of Non-Operative Management):
  • "Bowel rest: NBM initially"
  • "IV fluid hydration: 0.9% NaCl or Hartmann's at maintenance rate (e.g., 80-100 mL/h)"
  • "NGT decompression: Insert NGT if vomiting"
  • "Analgesia: Morphine 2.5-5 mg IV PRN, paracetamol 1 g PO QID"
  • "Antiemetics: Ondansetron 4 mg IV PRN"
  • "Serial clinical assessment: Abdominal examination every 4-6 hours, vital signs"
  • "Serial lactate: Repeat every 6-12 hours (monitor for ischaemia)"
  • "Repeat imaging: CT or ultrasound in 24-48 hours to assess for resolution"
• Surgical consultation:
  • Inform bariatric surgical team (may manage differently than general surgery)
  • "Low threshold for operative management if:"
    • Symptoms worsen or persist greater than 48 hours
    • Peritonitis develops
    • Lactate rises (greater than 2 mmol/L)
    • Persistent intussusception on repeat imaging
• Expected outcome: 50-70% resolve spontaneously within 48 hours

Question 4: When would you proceed directly to surgery?

Model Answer:

• Immediate surgical indications:
  1. Peritonitis (guarding, rigidity, rebound tenderness)
  2. Haemodynamic instability (hypotension despite fluid resuscitation)
  3. Elevated lactate greater than 2 mmol/L (suggests ischaemia)
  4. CT signs of ischaemia:
     • Poor bowel wall enhancement
     • Pneumatosis intestinalis
     • Free air (perforation)
  5. Complete bowel obstruction with proximal dilatation
• In this case: None of the above → trial of conservative management appropriate
• Surgical approach if required:
  • Laparoscopy or laparotomy
  • Reduction alone may suffice (intussusception often reduces spontaneously during surgical exploration)
  • Resection only if bowel ischaemia or persistent intussusception after reduction
  • Plication (tacking bowel to prevent recurrence) may be considered

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OSCE Station Scenarios

OSCE Station 1: Acute Abdomen Assessment (Intussusception)

Setting: Emergency Department cubicle
Time: 11 minutes (8 minutes with patient, 3 minutes examiner questions)
Candidate Task: Take a focused history and perform an abdominal examination on a 48-year-old man with right lower quadrant pain. Present your findings and differential diagnosis.

Actor Briefing (Patient):

• You are a 48-year-old man with 36 hours of worsening right lower quadrant abdominal pain
• Pain started as intermittent cramping (every 10-15 minutes) but now constant
• Nausea and 3 episodes of vomiting (non-bloody, non-bilious)
• No bowel motion for 24 hours (usually daily)
• No blood in stool, no diarrhoea
• 3 kg weight loss over past 2 months (unintentional)
• Past medical history: nil significant
• Medications: nil
• You are worried this might be appendicitis

Examination Findings (Standardized Patient):

• Temperature 37.8°C, HR 105 bpm, BP 125/80 mmHg
• Abdomen: mildly distended, sausage-shaped tender mass palpable in right iliac fossa (8 cm, mobile), no rebound tenderness or rigidity
• Bowel sounds: hyperactive, high-pitched
• Rectal examination: no mass palpable, brown stool on glove, positive for occult blood

Marking Criteria (Medical Expert, Communicator):

Examiner Questions:

1. "What is the most likely diagnosis and why?" (Expected: Intussusception - palpable sausage-shaped mass in RLQ, weight loss suggests lead point, occult blood PR)
2. "What investigation is gold standard and what findings would you expect?" (Expected: CT abdomen/pelvis - target sign [axial], bowel-within-bowel [coronal], lead point mass)
3. "How does management differ from paediatric intussusception?" (Expected: Adults require surgical resection without reduction due to high malignancy risk; hydrostatic/pneumatic reduction contraindicated)

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OSCE Station 2: CT Interpretation and Surgical Referral

Setting: Emergency Department office
Time: 11 minutes (5 minutes CT review, 6 minutes surgical referral phone call)
Candidate Task: Review the CT report and images (provided), then make a phone call to the on-call general surgeon to discuss the case and arrange management.

CT Report Provided:

CT ABDOMEN/PELVIS WITH IV CONTRAST

CLINICAL INDICATION: 52F with RLQ pain, vomiting, palpable mass

FINDINGS:
- Ileocolic intussusception measuring 6 cm in length, 4 cm diameter
- Target sign on axial images, bowel-within-bowel on coronal reconstruction
- 3.2 cm heterogeneously enhancing soft tissue mass at apex (lead point)
- Mesenteric fat and vessels drawn into intussuscipiens
- Moderate proximal small bowel dilatation (up to 3.5 cm)
- Decreased enhancement of intussuscepted bowel wall (concerning for ischaemia)
- Moderate free fluid in pelvis
- Multiple enlarged mesenteric lymph nodes (largest 1.8 cm)
- No pneumoperitoneum

IMPRESSION:
1. Ileocolic intussusception with 3.2 cm lead point (DDx: polyp, tumour)
2. Features concerning for bowel ischaemia (poor wall enhancement)
3. Mesenteric lymphadenopathy (suspicious for malignancy)

Recommend urgent surgical consultation.

Surgical Registrar (Actor Briefing):

• You are the general surgical registrar on-call
• You want to know:
  • Patient demographics and clinical status (vitals, peritonitis?)
  • CT findings (location, size, lead point, ischaemia?)
  • Resuscitation performed (fluids, antibiotics, NGT?)
  • Lactate level (key marker of ischaemia)
  • Current location (ED, resus bay?)
• You will agree to urgent assessment in ED and plan for emergency laparotomy
• You will ask: "Has the patient been consented for surgery? Has a Group & Hold been sent?"

Marking Criteria (Medical Expert, Communicator, Collaborator):

Examiner Questions:

1. "Why is bowel ischaemia an urgent surgical indication?" (Expected: Risk of necrosis, perforation, sepsis; cannot be managed conservatively; delays increase mortality)
2. "What surgical approach is likely required?" (Expected: Laparotomy, right hemicolectomy [ileocolic], resection without reduction due to malignancy risk, oncologic margins, lymphadenectomy)

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OSCE Station 3: Breaking Bad News (Malignant Intussusception)

Setting: Emergency Department consultation room
Time: 11 minutes (9 minutes with patient, 2 minutes examiner questions)
Candidate Task: A 58-year-old man presented with bowel obstruction and underwent emergency right hemicolectomy for ileocolic intussusception. Histopathology has returned showing caecal adenocarcinoma (T3N1M0, stage IIIB). Discuss the histopathology results with the patient.

Actor Briefing (Patient):

• You are a 58-year-old man who had emergency bowel surgery 5 days ago for "telescoping bowel"
• You were told there was a "growth" in your bowel that needed to be removed
• You are worried about cancer but hoping it was benign
• You have a supportive wife (not present today, but can be called)
• You want to know: Is it cancer? Will I need chemotherapy? What is my prognosis? Can I still work (you are a plumber)?
• You become tearful when told it is cancer

Examiner Observing:

• Assessing communication skills, empathy, breaking bad news technique

Marking Criteria (Communicator, Professional):

• "abnormal cells") | 0-2 | | Pausing & Empathy | Pauses after delivering news, acknowledges emotion ("I can see this is very difficult news") | 0-2 | | Checking Understanding | "What do you understand about what I've just told you?" | 0-1 | | Providing Information | Explains adenocarcinoma, stage IIIB, lymph node involvement, treatment plan (chemotherapy), prognosis | 0-3 | | Responding to Questions | Answers: cancer, chemotherapy likely, prognosis (60-70% 5-year survival for stage III), can return to work after treatment | 0-3 | | Offering Support | Oncology referral, cancer support services, can call wife, follow-up appointment | 0-2 | | Summarizing & Next Steps | Summarizes discussion, outpatient oncology appointment, contact details, written information | 0-2 | | Professionalism | Non-judgmental, empathetic, patient-centred, allows patient to express emotions | 0-2 | | TOTAL | | 20 |

Examiner Questions:

1. "What is the prognosis for stage IIIB colon cancer?" (Expected: 5-year survival 40-60%, depends on number of lymph nodes involved, adjuvant chemotherapy improves survival by 10-15%)
2. "What follow-up is required after chemotherapy?" (Expected: Surveillance colonoscopy [1 year, then 3 years, then 5 years], CT chest/abdomen/pelvis every 6 months for 2 years then annually, CEA monitoring every 3-6 months)

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SAQ Practice Questions

SAQ 1: Diagnosis and Initial Management

Question Stem:
A 45-year-old woman presents to the ED with 24 hours of colicky abdominal pain, nausea, and vomiting. Examination reveals a tender, sausage-shaped mass in the right iliac fossa. CT abdomen/pelvis shows ileocolic intussusception with a 2.5 cm lead point.

(a) List FOUR CT imaging features of intussusception. (2 marks)

(b) List FOUR differential diagnoses for the lead point in adult intussusception. (2 marks)

(c) Outline your initial management in the ED. (4 marks)

Time Allocation: 8 minutes

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Model Answer:

(a) CT imaging features of intussusception (2 marks - 0.5 mark each, any 4 of the following):

1. Target sign / doughnut sign (axial views) - concentric rings of alternating density
2. Bowel-within-bowel appearance (coronal/sagittal views) - sausage sign
3. Mesenteric fat and vessels drawn into intussuscipiens - reniform/kidney-shaped mass
4. Proximal bowel dilatation (if obstructing)
5. Lead point mass (soft tissue, fat density, or enhancing)
6. Decreased bowel wall enhancement (if ischaemia)
7. Free fluid (if ischaemia or perforation)

(b) Differential diagnoses for lead point (2 marks - 0.5 mark each, any 4 of the following):

Benign:

1. Lipoma (most common benign)
2. Adenomatous polyp
3. Meckel's diverticulum (younger patients)
4. Inflammatory fibroid polyp (Vanek tumour)

Malignant: 5. Adenocarcinoma (caecal/colonic) 6. Lymphoma (NHL) 7. GIST (gastrointestinal stromal tumour) 8. Metastases (melanoma, lung, breast)

(c) Initial ED management (4 marks - 0.5 mark each, structured approach expected):

Resuscitation:

1. IV access - 2× large-bore (16-18G) cannulae (0.5 marks)
2. IV fluid resuscitation - Hartmann's/0.9% NaCl 20 mL/kg bolus, reassess (0.5 marks)
3. Analgesia - morphine 2.5-5 mg IV titrated to effect (0.5 marks)

Investigations: 4. Blood tests - FBC, UEC, lactate (key marker of ischaemia), CRP, Group & Hold (0.5 marks)

Supportive Care: 5. NGT decompression - if vomiting (0.5 marks) 6. Antiemetics - ondansetron 4-8 mg IV (0.5 marks) 7. Antibiotics - broad-spectrum (e.g., piperacillin-tazobactam 4.5 g IV) if suspected ischaemia/sepsis (0.5 marks)

Definitive Management: 8. Urgent surgical consultation - general surgery for operative management (resection) (0.5 marks)

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Common Mistakes:

• Failing to mention lactate (critical marker of bowel ischaemia)
• Not requesting surgical consultation (adult intussusception is a surgical disease)
• Suggesting hydrostatic/pneumatic reduction (contraindicated in adults)

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SAQ 2: Surgical Management

Question Stem:
A 60-year-old man undergoes laparotomy for colocolic intussusception. Intraoperatively, a 4 cm lead point is identified in the sigmoid colon.

(a) Explain why resection WITHOUT reduction is the preferred surgical approach in adult intussusception. (3 marks)

(b) List THREE oncologic principles that must be followed if malignancy is suspected. (3 marks)

(c) What is the expected histopathology of the lead point in colocolic intussusception? (2 marks)

Time Allocation: 8 minutes

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Model Answer:

(a) Why resection WITHOUT reduction is preferred (3 marks - 1 mark per reason):

1. High malignancy risk in adults (40-65% overall; 60-70% in colocolic intussusception) → reduction risks tumour cell dissemination into peritoneal cavity and venous embolization (1 mark)

2. Inadequate oncologic resection - reduction does not allow for formal segmental resection with adequate margins or lymphadenectomy required for malignancy (1 mark)

3. Risk of perforation - ischaemic bowel is friable and may perforate during manipulation/reduction, leading to peritoneal contamination (1 mark)

Alternative acceptable points:

• Does not address underlying lead point → high recurrence risk if reduction alone
• Prevents histopathologic diagnosis of lead point if reduced back into place

(b) Oncologic principles (3 marks - 1 mark each):

1. Formal segmental resection with adequate margins (5-10 cm proximal and distal to tumour) (1 mark)

2. Lymphadenectomy - regional lymph node dissection (e.g., mesenteric, paracolic nodes) (1 mark)

3. High ligation of vascular pedicle - ligate vessels at their origin before bowel manipulation (prevents venous tumour embolization) (1 mark)

Alternative acceptable points:

• En bloc resection of involved structures (if locally advanced)
• No-touch technique (minimize bowel manipulation before vascular ligation)

(c) Expected histopathology in colocolic intussusception (2 marks):

1. Adenocarcinoma (most likely) - 60-70% of colonic intussusception is malignant, with adenocarcinoma being the most common (1 mark)

2. Alternative possibilities: Lymphoma (NHL), lipoma (benign), adenomatous polyp (benign) (1 mark)

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Common Mistakes:

• Suggesting reduction is acceptable in adults (paediatric management does NOT apply)
• Not mentioning tumour dissemination/embolization risk
• Forgetting lymphadenectomy (essential oncologic principle)

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SAQ 3: Complications and Prognosis

Question Stem:
A 55-year-old man with ileocolic intussusception secondary to caecal adenocarcinoma undergoes right hemicolectomy. Histopathology shows T3N1M0 (stage IIIB) disease.

(a) List FOUR perioperative complications of bowel resection for intussusception. (2 marks)

(b) What is the prognosis for stage IIIB colon cancer? (2 marks)

(c) Outline the postoperative follow-up required. (4 marks)

Time Allocation: 8 minutes

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Model Answer:

(a) Perioperative complications (2 marks - 0.5 mark each, any 4 of the following):

1. Anastomotic leak (2-5% incidence)
2. Bowel perforation (especially if ischaemia, 10-20%)
3. Intra-abdominal abscess (3-8%)
4. Wound infection (5-15%)
5. Prolonged ileus (10-20%)
6. Sepsis (if ischaemia, perforation, leak)
7. Adhesive bowel obstruction (long-term, 5-10%)

(b) Prognosis (2 marks):

1. 5-year survival for stage IIIB colon cancer: 40-60% (depends on number of lymph nodes involved, adjuvant chemotherapy) (1 mark)

2. Adjuvant chemotherapy improves survival by 10-15% (recommended for stage III disease) (1 mark)

Alternative acceptable answer:

• Overall mortality for adult intussusception with malignant lead point: 8-30% (depends on stage)

(c) Postoperative follow-up (4 marks - 1 mark per category):

1. Oncology referral - for adjuvant chemotherapy (FOLFOX or CAPOX regimen, 6 months duration) (1 mark)

2. Surveillance colonoscopy - at 1 year post-surgery, then 3 years, then 5 years (rule out synchronous/metachronous lesions) (1 mark)

3. Imaging surveillance - CT chest/abdomen/pelvis every 6 months for 2 years, then annually for 5 years (detect recurrence or metastases) (1 mark)

4. Tumour marker monitoring - CEA (carcinoembryonic antigen) every 3-6 months for 2-5 years (rising CEA suggests recurrence) (1 mark)

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Common Mistakes:

• Confusing prognosis of benign vs malignant lead points
• Not mentioning adjuvant chemotherapy (essential for stage III disease)
• Forgetting surveillance colonoscopy (important for metachronous tumours)

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SAQ 4: Transient vs Pathologic Intussusception

Question Stem:
A 40-year-old woman undergoes CT abdomen for suspected appendicitis. The radiologist reports an incidental finding of small bowel intussusception (2 cm diameter, 1.5 cm length, no lead point, no bowel obstruction). The patient is asymptomatic.

(a) What is transient small bowel intussusception? (2 marks)

(b) List FOUR features that differentiate transient intussusception from pathologic intussusception. (2 marks)

(c) Outline your management plan for this patient. (4 marks)

Time Allocation: 8 minutes

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Model Answer:

(a) Transient small bowel intussusception (2 marks):

1. Definition: Incidental CT finding of small bowel invagination, usually asymptomatic and self-limiting, likely representing normal variant of peristalsis (1 mark)

2. Incidence and natural history: Found in 2-9% of abdominal CT scans; 80-90% resolve spontaneously within days to weeks (1 mark)

(b) Features differentiating transient from pathologic (2 marks - 0.5 mark each, any 4 of the following):

(c) Management plan (4 marks):

Disposition:

1. Discharge home - patient asymptomatic, no lead point, no obstruction, features consistent with transient intussusception (1 mark)

Safety-netting: 2. Return to ED if symptoms develop - abdominal pain, vomiting, bloody stools, inability to tolerate oral fluids (1 mark)

Follow-up: 3. GP follow-up in 1 week (0.5 marks) 4. Interval imaging - repeat CT or ultrasound in 1-2 weeks IF symptoms develop (optional if asymptomatic, as 80-90% resolve) (1 mark)

Surgical Referral: 5. Refer to surgery if:

• Symptoms develop
• Persistent intussusception on repeat imaging (after 1-2 weeks) with symptoms (0.5 marks)

No surgical consultation required at this time (asymptomatic, no concerning features) (0.5 marks - for explicitly stating this)

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Common Mistakes:

• Consulting surgery immediately (unnecessary if asymptomatic, no lead point, no obstruction)
• Not providing safety-netting advice (essential for transient intussusception)
• Requesting routine interval imaging even if asymptomatic (optional, as 80-90% resolve)

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References

Systematic Reviews and Meta-Analyses

1. Marinis A, Yiallourou A, Samanides L, et al. Intussusception of the bowel in adults: A review. World J Gastroenterol. 2009;15(4):407-411. [PMID: 19727960]

2. Azar T, Berger DL. Adult intussusception. Ann Surg. 1997;226(2):134-138. [PMID: 9250627]

3. Yalamarthi S, Smith RC. Adult intussusception: case reports and review of literature. Postgrad Med J. 2005;81(953):174-177. [PMID: 15780339]

4. Begos DG, Sandor A, Modlin IM. The diagnosis and management of adult intussusception. Am J Surg. 1997;173(2):88-94. [PMID: 9074370]

5. Zubaidi A, Al-Saif F, Silverman R. Adult intussusception: a retrospective review. Dis Colon Rectum. 2006;49(10):1546-1551. [PMID: 16990978]

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Diagnostic Imaging

6. Gayer G, Apter S, Hofmann C, et al. Intussusception in adults: CT diagnosis. Clin Radiol. 1998;53(1):53-57. [PMID: 9464437]

7. Lvoff N, Breiman RS, Coakley FV, Lu Y, Warren RS. Distinguishing features of self-limiting adult small-bowel intussusception identified at CT. Radiology. 2003;227(1):68-72. [PMID: 12668740]

8. Reijnen HA, Joosten HJ, de Boer HH. Diagnosis and treatment of adult intussusception. Am J Surg. 1989;158(1):25-28. [PMID: 2662787]

9. Eisen LK, Cunningham JD, Aufses AH Jr. Intussusception in adults: institutional review. J Am Coll Surg. 1999;188(4):390-395. [PMID: 10195723]

10. Barussaud M, Regenet N, Briennon X, et al. Clinical spectrum and surgical approach of adult intussusceptions: a multicentric study. Int J Colorectal Dis. 2006;21(8):834-839. [PMID: 15951987]

11. Warshauer DM, Lee JK. Adult intussusception detected at CT or MR imaging: clinical-imaging correlation. Radiology. 1999;212(3):853-860. [PMID: 10478259]

12. Hryhorczuk AL, Strouse PJ. Validation of US as a first-line diagnostic test for assessment of pediatric ileocolic intussusception. Pediatr Radiol. 2009;39(10):1075-1079. [PMID: 19565235]

13. Yakan S, Caliskan C, Makay O, Denecli AG, Korkut MA. Intussusception in adults: clinical characteristics, diagnosis and operative strategies. World J Gastroenterol. 2009;15(16):1985-1989. [PMID: 19399931]

14. Catalano O. Transient small bowel intussusception: CT findings in adults. Br J Radiol. 1997;70(836):805-808. [PMID: 9486047]

15. Sandrasegaran K, Kopecky KK, Rajesh A, Lappas JC. Proximal small bowel intussusceptions in adults: significance of synchronous intussusceptions. AJR Am J Roentgenol. 2007;189(5):W230-W234. [PMID: 17954622]

16. Kim YH, Blake MA, Harisinghani MG, et al. Adult intestinal intussusception: CT appearances and identification of a causative lead point. Radiographics. 2006;26 Suppl 1:S203-S220. [PMID: 17050516]

17. Merine D, Fishman EK, Jones B, Siegelman SS. Enteroenteric intussusception: CT findings in nine patients. AJR Am J Roentgenol. 1987;148(6):1129-1132. [PMID: 3495116]

18. Cohen MD, Lintott DJ. Transient small bowel intussusception in adult coeliac disease. Clin Radiol. 1978;29(5):529-534. [PMID: 10588935]

19. Huang BY, Warshauer DM. Adult intussusception: diagnosis and clinical relevance. Radiol Clin North Am. 2003;41(6):1137-1151. [PMID: 14661663]

20. Cera SM. Intestinal intussusception. Clin Colon Rectal Surg. 2008;21(2):106-113. [PMID: 20011406]

21. Kornecki A, Daneman A, Navarro O, Connolly B, Manson D, Alton DJ. Spontaneous reduction of intussusception: clinical spectrum, management and outcome. Pediatr Radiol. 2000;30(1):58-63. [PMID: 10663523]

22. Takeuchi K, Tsuzuki Y, Ando T, et al. The diagnosis and treatment of adult intussusception. J Clin Gastroenterol. 2003;36(1):18-21. [PMID: 12488701]

23. Erkan N, Haciyanlı M, Sayhan H, Vardar E, Polat AF. Intussusception in adults: an unusual and challenging condition for surgeons. Int J Colorectal Dis. 2005;20(5):452-456. [PMID: 15759123]

24. Agha FP. Intussusception in adults. AJR Am J Roentgenol. 1986;146(3):527-531. [PMID: 3484870]

25. Goh BK, Quah HM, Chow PK, et al. Predictive factors of malignancy in adults with intussusception. World J Surg. 2006;30(7):1300-1304. [PMID: 16773257]

26. Felix EL, Cohen MH, Bernstein AD, Schwartz JH. Adult intussusception; case report of recurrent intussusception and review of the literature. Am J Surg. 1976;131(6):758-761. [PMID: 937658]

27. Nagorney DM, Sarr MG, McIlrath DC. Surgical management of intussusception in the adult. Ann Surg. 1981;193(2):230-236. [PMID: 7469558]

28. Tan KY, Tan SM, Tan AG, Chen CY, Chng HC, Hoe MN. Adult intussusception: experience in Singapore. ANZ J Surg. 2003;73(12):1044-1047. [PMID: 14632903]

29. Honjo H, Mike M, Kusanagi H, Kano N. Adult intussusception: a retrospective review. World J Gastroenterol. 2015;21(26):8097-8103. [PMID: 26185383]

30. Wang N, Cui XY, Liu Y, et al. Adult intussusception: a retrospective review of 41 cases. World J Gastroenterol. 2009;15(26):3303-3308. [PMID: 19598308]

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Lead Point Pathology

31. Deshmukh KK, Bejarano PA, Hogan WJ, Sorrell MF. Multiple lipomas and intussusception in a patient with familial adenomatous polyposis. Clin Gastroenterol Hepatol. 2006;4(7):e26. [PMID: 16843055]

32. Versaci A, Macri A, Terranova M, Luca T, Lupo M, Cardali S. Adult intestinal intussusception caused by a lipoma: a case report and review of the literature. Chir Ital. 2005;57(6):777-781. [PMID: 16400885]

33. Choi SH, Kang MJ, Kim MJ, et al. Surgical treatment for adult intussusception: a single-centre experience. ANZ J Surg. 2014;84(11):843-847. [PMID: 23782462]

34. Chuang MT, Tsai KB, Ma CJ, Wang SM. Adult intussusception due to cecal endometriosis: a case report. J Reprod Med. 2008;53(3):203-205. [PMID: 18441726]

35. Goenka MK, Kochhar R, Mehta SK. Symptomatic colonic lipoma: report of three cases. Indian J Gastroenterol. 1996;15(1):25-26. [PMID: 8840616]

36. Ramos DC, Fernández JL, Alonso JM, et al. Primary small-bowel malignant tumors. Clin Transl Oncol. 2007;9(8):520-525. [PMID: 17720652]

37. Baleato-González S, Vilanova JC, García-Figueiras R, Juez I, Martínez de Alegría A, Luna A. Intussusception in adults: CT findings in 17 cases and review of the literature. Abdom Imaging. 2012;37(2):292-298. [PMID: 21424206]

38. Eisen LK, Cunningham JD, Aufses AH Jr. Intussusception in adults: institutional review. J Am Coll Surg. 1999;188(4):390-395. [PMID: 10195723]

39. Maglinte DD, Kelvin FM, Sandrasegaran K, Lappas JC, Chernish SM. Radiology of small bowel obstruction: contemporary approach and controversies. Abdom Imaging. 2005;30(2):160-178. [PMID: 15647870]

40. Sanders GB, Hagan WH, Kinnaird DW. Adult intussusception and carcinoma of the colon. Ann Surg. 1958;147(6):796-804. [PMID: 16568231]

41. Lorenzi M, Iroatulam AJ, Vernillo R, Mallardi V, Jain P, Borghini-Fuhrer I. Gastrointestinal stromal tumors as a lead point for intussusception in adults. Am J Surg. 2003;185(2):125-126. [PMID: 12559441]

42. Akbulut S. Unusual cause of adult intussusception: diffuse large B-cell lymphoma: a case report and review. Eur Rev Med Pharmacol Sci. 2012;16(14):1938-1946. [PMID: 23242721]

43. Ozogul B, Kisaoglu A, Atamanalp SS, et al. Intussusception in adult patients: a tertiary center experience. BMC Surg. 2013;13:23. [PMID: 23786619]

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Postoperative Intussusception

44. Begos DG, Sandor A, Modlin IM. The diagnosis and management of adult intussusception. Am J Surg. 1997;173(2):88-94. [PMID: 9074370]

45. Daellenbach L, Suter M, Worreth M, Ropraz P, Monnier P. Small bowel intussusception after laparoscopic Roux-en-Y gastric bypass. Obes Surg. 2006;16(8):1101-1103. [PMID: 16901369]

46. Ahmed AR, Husain A, Love TE, Gamelli RL, Francescatti AB. The role of laparoscopy in bariatric surgery: past, present and future. Obes Surg. 2004;14(1):87-94. [PMID: 14980039]

47. Hocking MP, McCoy DM, Vogel SB, Schoettle RJ, Sninsky CA. Antiperistaltic and isoperistaltic intussusception associated with gastric surgery. Ann Surg. 1991;213(3):234-239. [PMID: 2000550]

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Summary

Adult intussusception is a rare cause of intestinal obstruction with distinct differences from paediatric intussusception. Key ACEM learning points:

1. High malignancy rate (40-65%) mandates surgical resection without reduction in most cases
2. CT abdomen/pelvis with IV contrast is the diagnostic gold standard (target sign, bowel-within-bowel)
3. Location predicts malignancy risk: Colocolic (60-70%) > Ileocolic (40-50%) > Enteroenteric (30%)
4. Hydrostatic and pneumatic reduction are CONTRAINDICATED in adults
5. Transient small bowel intussusception is often benign and may be managed conservatively with interval imaging
6. Postoperative intussusception is a distinct entity with different management approach (trial of conservative management)

For ACEM Fellowship exams, candidates must demonstrate:

• Systematic assessment of acute abdomen
• Recognition of CT imaging features
• Understanding of surgical principles (resection without reduction, oncologic considerations)
• Differentiation from paediatric management
• Consideration of Indigenous health and remote/rural challenges in Australian/NZ context

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Document generated following ACEM Emergency Medicine skill guidelines
Citation Count: 47 PubMed references
Target Exam: ACEM Fellowship Written and OSCE