Acute vomiting in infants and children: Viva

Branch 1: Recognising the time-critical problem

The candidate must immediately recognise that bilious vomiting in a neonate is malrotation with midgut volvulus until proven otherwise, and that this is a surgical emergency rather than a cause for reassurance or an outpatient referral. The green vomit, the fullness of the abdomen, the change from a well-feeding baby, and the failure to pass stool all point to obstruction, and a volvulus can infarct the entire midgut within hours. The single most important statement is that any delay costs bowel. [1]

The candidate should state the first actions in parallel: make the baby nil by mouth, place a nasogastric tube on free drainage to decompress the stomach, obtain intravenous access, start fluid resuscitation, check a glucose, and call the paediatric surgical team immediately. Investigations follow but do not delay the surgical call in an unwell baby. [1]

Branch 2: Confirming the diagnosis and the decision to operate

The examiner will ask how the candidate would confirm the diagnosis. In a stable infant, the investigation of choice is an urgent upper gastrointestinal contrast study, which shows an abnormally placed duodenojejunal flexure and the corkscrew appearance of a volvulus. An ultrasound may show an abnormal relationship of the superior mesenteric vessels. The candidate should be clear, though, that a shocked baby or one with a surgical abdomen and signs of peritonitis goes straight to theatre without waiting for imaging. [1]

The examiner may probe why the delay matters so much. The strong candidate explains that the midgut, from the duodenum to the mid-transverse colon, hangs on the narrow pedicle of the superior mesenteric artery when malrotation is present, so a twist strangles the blood supply to the whole small bowel, and prompt operative detorsion and a Ladd procedure are the only way to save it. Published delay data confirm that late recognition of bilious vomiting still causes preventable bowel loss. [1]

Branch 3: Broadening to the age-based differential

The examiner will then broaden the discussion to how the candidate would think about vomiting more generally. The candidate should offer a structured framework: split first by the colour of the vomit into bilious versus non-bilious, then by age, then by the surgical, medical and non-gastrointestinal buckets. In the neonate the priorities are malrotation, necrotising enterocolitis, congenital obstruction, sepsis and inborn errors of metabolism, while in the older infant pyloric stenosis, gastroenteritis and intussusception dominate. [2]

The examiner may ask what would make the candidate think of a cause outside the gut. The candidate should name the mimics: diabetic ketoacidosis, sepsis, urinary tract infection and raised intracranial pressure, and should state that a glucose is mandatory in every seriously vomiting child and that early-morning vomiting with headache or abnormal eye movements points to raised intracranial pressure. [2]

Branch 4: The common problem and the fluid decision

The examiner will pivot to the common scenario of gastroenteritis. The candidate should describe grading dehydration with a validated clinical scale, and then choosing the least invasive effective route: oral rehydration solution given in small frequent amounts is first-line for mild and moderate dehydration and is as effective as intravenous fluids with fewer complications. Breastfeeding continues throughout, and early refeeding follows. [2]

The examiner will ask about the role of antiemetics. The strong candidate explains that a single dose of oral ondansetron reduces vomiting, improves the success of oral rehydration, and reduces the need for intravenous fluids and admission, and that it is used selectively to rescue oral rehydration rather than routinely. Metoclopramide and prochlorperazine are avoided in young children because of extrapyramidal side effects, and antiemetics are never given to an undiagnosed or surgical abdomen where they mask progression. [3]

Branch 5: Safety-netting and disposition

The examiner will finish by asking how the candidate would advise a family of a child discharged with gastroenteritis. The candidate should give a specific, behaviour-based safety-net: offer small frequent sips of oral rehydration solution, and return immediately if the vomit turns green or bloody, if the child becomes drowsy or floppy, if there is severe or constant abdominal pain, or if the child cannot keep any fluid down or stops passing urine. Checking that the family can repeat the warning signs back confirms understanding. [2]

The candidate should state the admission thresholds: failed oral rehydration, moderate-to-severe or worsening dehydration, a suspected surgical or metabolic cause, an unwell or high-risk young infant, and social circumstances that make safe home care unlikely. This closes the loop from the emergency at the start of the viva to the safe discharge of the common case. [2]