Meckel's Diverticulum
Summary
Meckel's diverticulum is the most common congenital anomaly of the gastrointestinal tract, occurring in approximately 2% of the population. It is a "true" diverticulum (containing all layers of the bowel wall) resulting from the incomplete obliteration of the vitelline (omphalomesenteric) duct. While most are asymptomatic, complicatons such as bleeding, obstruction, and inflammation can occur, particularly in children under 2 years of age. [1,2]
The "Rule of 2s"
- 2% of the population.
- 2 feet (60cm) from the ileocecal valve.
- 2 inches (5cm) long.
- 2 types of ectopic tissue (Gastric and Pancreatic).
- 2:1 Male to Female ratio.
- 2 years: Most common age for symptomatic presentation.
Clinical Pearls
The "Silent Bleeder": The classic presentation is painless rectal bleeding in a young child. The blood is typically "brick red" or maroon. This bleeding is caused by ectopic gastric mucosa within the diverticulum secreting acid, which ulcerates the adjacent normal ileum (not the diverticulum itself).
The "Appendicitis Mimic": Meckel's Diverticulitis presents almost identically to Appendicitis (RIF pain, fever, vomiting). If you operate for appendicitis and find a normal appendix, you MUST examine the distal 2 feet of ileum to rule out an inflamed Meckel's.
Intussusception Lead Point: While most childhood intussusception is idiopathic (swollen Peyer's patches), a Meckel's diverticulum can act as a pathological "lead point" dragging the bowel into itself. This type is less likely to reduce with air enema and usually requires surgery.
Demographics
- Prevalence: 2% globally.
- Symptomatic Rate: Only 4-6% of people with a Meckel's ever develop symptoms.
- Age: 50% of symptomatic patients present before age 2.
Embryology
- The Vitelline Duct connects the fetal midgut to the yolk sac.
- Normally, it obliterates by week 7 of gestation.
- Failure of obliteration results in a spectrum of anomalies:
- Meckel's Diverticulum (98%): Proximal part remains patent.
- Umbilical Sinus: Distal part remains patent.
- Vitelline Fistula: Patent connection bowel-to-umbilicus (fecal discharge).
- Fibrous Band: Obliterated but persists as a cord (risk of volvulus).
Histology
- Heterotopia: 50% contain ectopic tissue.
- Gastric: Acid secretion -> Peptic ulceration -> Bleeding/Perforation.
- Pancreatic: Alkaline secretion -> Inflammation.
Symptoms
Signs
- General: assessing hydration and perfusion is priority.
- Abdomen: Palpate RIF. Check Hernial orifices.
- PR Exam: Confirm presence of blood (and exclude anal fissure).
Diagnosis
- Meckel's Scan (Technetium-99m Pertechnetate):
- The Isotope is taken up by gastric mucosa (stomach and ectopic tissue).
- Positive Scan: "Hot spot" in RIF appearing at same time as stomach.
- Note: Sensitivity ~85%. False negatives if no gastric mucosa present or active bleeding washes isotope away.
- Priming: H2-blockers (Ranitidine) generally given before scan to enhance uptake.
Bloods
- FBC: Hb (Anaemia).
- Crossmatch: Vital for bleeds.
Imaging
- Ultrasound / CT: Usually normal unless obstructed/inflamed. May show "blind ending tubular structure".
Management Algorithm
CHILD WITH RECTAL BLEEDING
(Painless)
↓
RESUSCITATE & STABILISE
- IV Access / Fluids
- Crossmatch Blood
- Rule out Anal Fissure / Infectious Colitis
↓
SUSPECT MECKEL'S?
(Brick red blood)
↓
MECKEL'S SCAN
┌───────────┴───────────┐
POSITIVE NEGATIVE
↓ ↓
SURGERY OBSERVE / COLONOSCOPY
(Resection) (Ruling out polyps/IBD)
Surgical Options
- Wedge Resection: Removing the diverticulum and closing the base. Appropriate for simple diverticulitis.
- Segmental Resection: Removing the segment of ileum containing the diverticulum. Mandatory for bleeding cases to ensure the adjacent ulcerated ileum is removed (otherwise bleeding recurs).
Incidental Finding?
- If found during other surgery (e.g., appendectomy):
- Children: Usually resected (prevent future complications).
- Adults: Usually left alone (risk of complication decreases with age) unless clear palpable thickening suggests ectopic tissue.
- Haemorrhage: Life threatening.
- Perforation: Peritonitis.
- Obstruction: Bowel Ischaemia.
- Mortality: Near 0% with elective surgery. 1-2% in emergency/perforated cases.
- Recurrence: None after resection.
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| Paediatric GI Bleed | NASPGHAN | Algorithm for evaluating rectal bleeding. Meckel's scan indicated for painless. |
| Surgical Mgmt | BAPS | Resect adjacent ileum in bleeding cases. |
Landmark Evidence
1. Segmental vs Wedge Resection
- Studies confirm that simple diverticulectomy (wedge) is insufficient for bleeding Meckel's because the ulcer sits in the native ileum opposite the opening. Segmental resection is gold standard.
What is a Meckel's Diverticulum?
It is a small extra pouch on the small intestine. It is a leftover from the umbilical cord connection when the baby was growing in the womb. About 2 in every 100 people have one.
Why is it bleeding?
Often, the pouch contains stomach lining cells. Just like the stomach, these cells make acid. But the intestine isn't built to handle acid, so it burns the lining, causing an ulcer that bleeds.
Is it serious?
The bleeding can be heavy, but it stops once we remove the pouch.
What is the operation?
It is keyhole surgery (laparoscopy) to find the pouch and cut it out. We usually remove a small piece of the intestine with it to make sure we get the ulcer too, then join the ends back together.
Primary Sources
- Sagar J, et al. Meckel's diverticulum: a systematic review. J R Soc Med. 2006.
- Menezes M, et al. Symptomatic Meckel's diverticulum in children: a 16-year review. Pediatr Surg Int. 2008.
Common Exam Questions
- Rule: "Rule of 2s?"
- Answer: 2%, 2 feet, 2 inches, 2 years, 2 types tissue.
- Diagnosis: "Investigation for painless bleeding?"
- Answer: Technetium-99m Pertechnetate Scan.
- Pathology: "Cause of bleeding?"
- Answer: Ectopic Gastric Mucosa -> Acid -> Peptic Ulceration of Ileum.
- Anatomy: "Antimesenteric or Mesenteric?"
- Answer: Anti-mesenteric border.
Viva Points
- Littre's Hernia: What is it? An inguinal/femoral hernia containing a Meckel's diverticulum.
- False Negative Scan: Why? 1. No gastric mucosa present (bleeding from another cause?). 2. Rapid bleeding washed the tracer away.
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.