Intussusception — branching viva

Opening — framing the problem

The examiner begins: a previously well seven-month-old has had four hours of episodes of screaming, going pale and drawing up the knees, with a drowsy interval between them, and has vomited twice. Talk me through your approach. [1]

I would frame this as intussusception, the commonest cause of bowel obstruction in an infant, and recognise the rhythmic pattern of peristalsis-driven colic as itself the key clue. My priorities would be to assess and resuscitate, to confirm the diagnosis with ultrasound, and to involve the surgeon and radiologist early, because early enema reduction is curative in most and delay risks the bowel. [1] [2]

Branch A — confirming the diagnosis

How would you confirm it, and what sign would you expect? [5]

I would arrange an abdominal ultrasound as the first-line investigation, which has a sensitivity in the high nineties. The diagnostic sign is the target sign on the transverse view, the concentric alternating rings of the oedematous telescoped bowel wall, and the pseudokidney sign on the longitudinal view. Feeling the sausage-shaped mass in the right upper quadrant during a quiet interval, which I would palpate for, would already make the diagnosis highly likely. [5] [2]

Branch B — resuscitation before reduction

What would you do before any attempt at reduction? [6]

I would make the child safe first. I would keep him nil by mouth, secure intravenous access, pass a nasogastric tube on free drainage to decompress the stomach, and give an intravenous bolus of ten to twenty millilitres per kilogram of isotonic crystalloid, reassessing for dehydration. I would provide analgesia and check the glucose, and I would have the paediatric surgeon and radiologist present for the reduction. I would examine specifically for tenderness and guarding, because peritonitis would contraindicate an enema. [6] [2]

Branch C — the definitive treatment

The ultrasound confirms the target sign. What is the treatment, and why that choice? [3]

Non-operative enema reduction is the treatment of choice for a stable child without peritonitis, and I would use air enema rather than liquid or contrast enema. A meta-analysis showed air reduction achieves a higher success rate, is faster, uses less radiation and makes any perforation easier to manage than liquid contrast, and it succeeds in roughly three-quarters to four-fifths of attempts. I would reserve surgery for a failed reduction or for signs of peritonitis or ischaemia. [3] [6]

Branch D — the pivot to the older child

Now a four-year-old presents similarly, but two attempts at air enema fail to reduce it. What changes? [7]

The age changes the suspicion. In a child over three years a pathological lead point is far more likely, so I would think of a Meckel diverticulum, a juvenile polyp, an intestinal lymphoma or a duplication cyst, and I would expect surgery rather than further enema. After failed enema reduction the child proceeds to a laparoscopic or open manual reduction, with resection of any non-viable bowel and of the lead point that is found. [7] [6]

Closing — the vaccine question

A parent asks whether the rotavirus vaccine their baby is due to receive causes intussusception. What do you say? [9]

I would explain that oral rotavirus vaccine carries a small, well-recognised excess risk of intussusception in the week after the first dose, but that the absolute risk is tiny and the benefit in preventing severe dehydrating rotavirus disease overwhelmingly outweighs it. On that basis I would recommend the vaccine on schedule and not delay it, which is the consistent position of immunisation authorities in Australia, New Zealand and worldwide. [9] [1]