Necrotising enterocolitis and spontaneous intestinal perforation — formative SAQs

SAQ 1 — The deteriorating preterm with established NEC (10 marks)

A 26-week, 780 g infant is day 9 of life, established on formula feeds. Over 12 hours the gastric residuals have increased and become bilious, the abdomen is distended and tender, and the infant has had three apnoeic spells requiring stimulation. Abdominal radiograph shows bubbly lucency in the bowel wall of the terminal ileum and branching lucency over the liver. The platelet count has fallen from 220 to 90 × 10⁹/L and the capillary gas shows a base excess of −8. ^[3]

a) Give the diagnosis, the radiological stage, and two signs that mark this as severe disease. (3 marks) ^[1]

The diagnosis is necrotising enterocolitis (NEC). The bubbly bowel-wall lucency is pneumatosis intestinalis and the branching liver lucency is portal venous gas, which places this at modified Bell Stage IIB (definite NEC, moderate). Two signs of severity are the portal venous gas itself (a marker of advanced, often pan-intestinal disease) and the falling platelet count with metabolic acidosis, indicating systemic deterioration towards Stage III. ^{[1] [3]}

b) Outline the immediate medical bundle, including the antibiotic principle and the planned duration of gut rest. (4 marks) ^[3]

Make the infant nil by mouth for 7 to 14 days depending on the course, and pass a large-bore nasogastric tube for free drainage and decompression. Take blood, urine and CSF cultures. Start broad-spectrum antibiotics with anaerobic cover — a gram-negative agent plus metronidazole or clindamycin, adjusted to local resistance and to any positive cultures — for a duration of 7 to 14 days for established NEC, prolonged if perforation or ongoing sepsis occurs. ^[3]

c) State three surgical triggers that would prompt urgent operative intervention, and describe the operative options for a perforated infant. (3 marks) ^[4]

Three surgical triggers are: a new pneumoperitoneum; a fixed and persistent loop with clinical deterioration; and abdominal wall discolouration with shock, or a positive diagnostic paracentesis (brown or bile-stained fluid, bacteria on Gram stain). 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 NET trial found PD did not improve survival versus laparotomy, so the choice is individualised. ^{[4] [13]}