The deteriorating preterm — suspected necrotising enterocolitis

Clinical information for the examiner

Setting: Tertiary NICU, day 9 of life. The infant was born at 26 weeks to a mother who received one dose of antenatal corticosteroid; one dose of surfactant was given at birth for respiratory distress syndrome. Feeds were advanced on formula to 120 mL/kg/day by day 8. [1]

On your arrival:

• Heart rate 168 (was 150), respiratory rate 65 with increased work, SpO₂ 88% in air. [3]
• Temperature 36.9°C but capillary refill 4 seconds; blood pressure 38/24 (mean 28). [1]
• Abdomen is distended and tender, with mild erythema of the lower abdominal wall; bowel sounds are absent. A nasogastric tube is draining 28 mL of bilious fluid. [3]
• Recent bloods: platelets 90 × 10⁹/L (was 220), CRP 42, base excess −8. [1]
• Abdominal radiograph: pneumatosis intestinalis in the terminal ileum and portal venous gas over the liver; no free air. [3]

Task 1 — Focused assessment and staging (3 marks)

The candidate should perform an ordered assessment. [1] [3]

Inspect the abdomen for distension, asymmetry and wall erythema/oedema; palpate gently for tenderness, guarding and a palpable fixed loop; auscultate for bowel sounds (absent here); then assess perfusion — capillary refill, blood pressure and pulse quality. The candidate should read the radiograph aloud, naming pneumatosis intestinalis and portal venous gas, and should state the modified Bell stage (IIB) with a one-line justification. [1] [2]

Must-hit points: pneumatosis as the hallmark; portal venous gas as a severity marker; Stage IIB; recognition that absent bowel sounds and wall erythema signal peritonitis. [1]

Task 2 — The immediate medical bundle (4 marks)

The candidate must give the bundle in full. [3]

• Nil by mouth for 7 to 14 days depending on the course. [1]
• Large-bore nasogastric tube for free drainage and decompression (already in place).
• Cultures: blood, urine and CSF. [3]
• Broad-spectrum antibiotics with anaerobic cover — a gram-negative agent plus metronidazole or clindamycin, adjusted to local resistance and positive cultures. [3]
• Resuscitation in parallel: isotonic fluid boluses for hypotension, inotropes if needed, correction of acidosis and coagulopathy, and respiratory support. [1]
• Serial monitoring: abdominal exam and girth, bloods (platelets, gas, CRP) and abdominal radiograph every 6 to 12 hours. [1]

Must-hit points: the anaerobic-cover principle is the antibiotic key; gut-rest duration of 7 to 14 days; resuscitation runs in parallel, not after. [3]

Task 3 — The surgical trigger and the operative options (3 marks)

The candidate must name the trigger and the options. [4]

The surgical triggers are: a new pneumoperitoneum; a fixed and persistent loop with clinical deterioration (the loop that does not change on serial films is dead bowel); abdominal wall discolouration with shock; or a positive diagnostic paracentesis (brown or bile-stained fluid, bacteria on Gram stain). [1] [13]

The operative options for perforation are primary peritoneal drainage (a bedside right-lower-quadrant catheter draining gas and meconium, used for ELBW or unstable infants as bridge or sole therapy) and laparotomy (resection of necrotic bowel with stoma or, in selected cases, primary anastomosis). The candidate should cite the NET trial (Rees 2008): PD did not improve survival versus laparotomy in ELBW infants with perforated NEC, so the choice is individualised. [4]

Must-hit points: the trigger is met before the antibiotic course completes; the fixed loop is dead bowel; the NET trial frames the PD-versus-laparotomy choice. [4] [13]

Task 4 — Contrast with spontaneous intestinal perforation (2 marks)

The examiner now changes the picture: "Suppose instead a day-6, 560 g infant exposed to early indomethacin and dexamethasone is found to have an isolated pneumoperitoneum on a routine film, with no pneumatosis, no portal gas, and a stable, well infant. What is different?" [7]

The candidate should recognise spontaneous intestinal perforation (SIP). The three discriminators are: the infant is haemodynamically stable; there is no pneumatosis and no portal gas; and the risk profile fits — an ELBW infant exposed to early postnatal indomethacin combined with glucocorticoid (antenatal steroids carry no adverse SIP association). [7] [11]

The management and prognosis differ: SIP is often managed definitively with primary peritoneal drainage alone, with targeted antibiotics and far less sepsis resuscitation, and SIP mortality (~10 to 15%) is markedly better than perforated NEC (~20 to 30%). Over-treating a SIP infant with an aggressive NEC laparotomy is the classic trap. [7] [4]

Must-hit points: name SIP; state that antenatal steroids do not raise SIP risk while postnatal indomethacin plus steroid does; recognise PD-alone as often definitive; better prognosis than perforated NEC. [7] [11]