The surgical newborn — bilious vomiting with a double-bubble

Clinical information for the examiner

Setting: Postnatal ward, 18 hours of life. Term male infant, spontaneous vaginal delivery, birth weight 3.1 kg. Pregnancy was complicated by polyhydramnios; antenatal ultrasound showed a double-bubble. Apgars were 9 and 9. [4]

On your arrival:

• The infant is alert but mildly dehydrated; the anterior fontanelle is slightly sunken. [10]
• Vomit is documented as "green, bile-stained" — the colour test is positive. [1]
• The abdomen is soft, non-distended and non-tender (a proximal obstruction pattern). [10]
• The perineum shows a normal patent anus in the correct position, excluding an anorectal malformation. [10]
• Dysmorphic features consistent with Down syndrome are noted (brushfield spots, single palmar crease, hypotonia). [4]

Investigation provided: A plain abdominal radiograph shows two large gas-filled structures in the upper abdomen (the stomach and the dilated proximal duodenum) with no distal bowel gas — the classic double-bubble. [4]

Task 1 — Focused assessment and the colour test (3 marks)

The candidate should perform an ordered assessment and act on the colour. [1] [10]

1. Recognise the colour: document that the vomit is green (bilious) — this is the trigger for the whole pathway. [1]
2. Assess hydration and perfusion: sunken fontanelle, capillary refill, vital signs — resuscitate in parallel. [10]
3. Examine the abdomen: soft and non-distended suggests a proximal obstruction. [10]
4. Inspect the perineum: confirm a patent anus, excluding an anorectal malformation. [10]
5. Note the Down syndrome features and link them to the diagnosis. [4]

Pass criterion: candidate identifies the bilious vomit as obstruction, notes the proximal (non-distended) pattern, inspects the perineum, and links the Down syndrome features to duodenal atresia. [4]

Task 2 — Immediate management in order (4 marks)

The candidate gives the fixed, non-negotiable sequence before any further imaging. [10]

• NPO — nil by mouth immediately. [10]
• Large-bore NG tube (10–12 French) on free drainage — not a fine-bore tube, which blocks. [10]
• IV access and isotonic crystalloid resuscitation (10 mL/kg boluses), with glucose and electrolyte correction. [10]
• Broad-spectrum antibiotics, because surgery is imminent and NEC is a differential. [10]
• Urgent paediatric surgical and neonatal referral. [10]

Pass criterion: candidate gives the sequence in the correct order and explains why a large-bore tube is essential. [10]

Task 3 — Diagnosis, imaging and the association (3 marks)

• The plain radiograph shows a double-bubble (stomach and proximal duodenum) with no distal gas, confirming complete duodenal obstruction — duodenal atresia. [4]
• In this stable infant with a diagnostic radiograph, no further contrast study is required — proceed to surgery. [4]
• The Down syndrome association (~30% of duodenal atresia) requires a karyotype and an echocardiogram before surgery to exclude the cardiac anomalies (classically an endocardial cushion defect) that shape the anaesthetic risk. [4]

Pass criterion: candidate names duodenal atresia, recognises the double-bubble as sufficient, and requests the cardiac and genetic workup. [4]

Task 4 — Definitive surgery, prognosis and pitfalls (2 marks)

• Definitive operation: diamond-shaped duodenoduodenostomy (Kimura procedure), bypassing the atresia; an annular pancreas, if found, is bypassed and never divided. [4]
• Prognosis: excellent after elective repair, with near-normal gastrointestinal function; outcome governed by the cardiac and chromosomal associations. [4]
• Pitfall to name: the danger of attributing the green vomit to a feeding problem or swallowed bile — the classic error that delays diagnosis; the candidate should contrast this stable infant with the volvulus trap, where an unstable infant goes straight to theatre without contrast. [5]