Branching cross-examination

This is a MedVellum formative viva. It is not an official RACP, MRCPCH, ABP, ACGME or RCPSC station, mark scheme, duration or pass standard. Release each update only after the candidate states the failing system, the immediate action and the reassessment endpoint. [1] [2]

Candidate brief

You are the senior paediatric clinician in a rural district emergency department. Speak as you would during resuscitation. Secure immediate threats before the diagnosis is certain, state the change you expect from each action, and say what you will reassess. This is one continuous case. Each escalation branch leads to the next update. [2]

Question 1 — Doorway and the first 60 seconds

Stimulus update. A parent carries a four-year-old who is drooling and refusing drinks. The parent found a remote control missing a twenty-millimetre lithium battery about two hours ago. Before you touch the child you see drooling, a soft stridor at rest, and a child who is alert but uncomfortable. Question: What do you say and do now? [1]

Consultant-level model answer. "I am immediately concerned about an oesophageal button battery with a threatened airway. I call the senior paediatrician, endoscopist, anaesthetist and ENT or surgical teams now, name a leader, allocate roles, and bring age- and weight-appropriate equipment and monitoring. I keep the child nil by mouth, give oxygen, position for airway safety, and prepare to protect the airway if the stridor worsens or haematemesis develops. The time since ingestion is already two hours, so the removal clock is running, and I am mobilising endoscopy within the two-hour target. Stabilisation precedes diagnosis." [1] [8]

Probing follow-up. "Why secure the airway and call the endoscopy team before you image?" A strong answer is: "Because the airway and the clock are the two time-critical threats. Drooling and stridor place the battery in the oesophagus and threaten the airway, and the two-hour removal target is already at risk. Imaging is decisive but it follows airway safety and team mobilisation." [1] [5]

Common weak answer. "I will order a chest X-ray and wait for the report." Imaging follows airway safety and team mobilisation, and a single film nasopharynx to anus is the standard, not a chest film alone. [2]

Escalation branch. If the candidate secures the airway and mobilises the team, release the radiograph in Question 2. If they anchor on imaging first, ask which failing system they will treat while it is arranged. [1]

Question 2 — The radiograph and the halo sign

Stimulus update. The airway is stable with oxygen, access is established, and the team is assembling. The radiograph shows a round density in the upper oesophagus with a halo and a step-off on the lateral view. Question: How do you interpret this, and what is the removal target? [1] [2]

Consultant-level model answer. "The halo and double-ring on the AP view and the step-off on the lateral view confirm this is a button battery, not a coin. It is lodged in the upper oesophagus, so this is a time-critical emergency. The removal target is endoscopic removal within two hours of presentation, regardless of symptoms, by a senior endoscopist with anaesthetic and surgical or ENT standby. The injury can begin within two hours of contact and rises steeply thereafter." [1] [5]

Probing follow-up. "Why image nasopharynx to anus rather than the chest alone?" A strong answer is: "A single film from nasopharynx to anus in AP and lateral localises the object, confirms oesophageal versus gastric position, distinguishes a battery from a coin, and counts any magnets. A chest film alone would miss a battery at the cricopharyngeus or a magnet in the stomach." [2]

Common weak answer. "The round density is probably a coin, so I will observe." A coin is smooth and single-density without a halo, double-ring or step-off. [1]

Escalation branch. If the candidate confirms the battery and the two-hour target, release in Question 3 that the child is over twelve months and can swallow. If they plan to observe, ask them to re-examine the signs for a battery. [1] [6]

Question 3 — The honey adjunct and its limits

Stimulus update. The child is four years old, drooling but able to swallow safely, with no airway compromise, no suspected perforation, no sepsis and no honey allergy. Endoscopy can begin in twenty minutes. Question: What do you give while awaiting removal, and what are its limits? [6] [7]

Consultant-level model answer. "I give honey 10 millilitres, roughly two teaspoons, by mouth every ten minutes for up to six doses while awaiting endoscopy. The alternative is sucralfate 1 gram per 10 kilograms. The mechanism is that honey and sucralfate reduce the pH at the negative pole and limit hydroxide generation, buying time within the removal window. The limits are absolute: the adjunct never replaces or delays endoscopy, and honey is contraindicated in infants under twelve months because of the botulism risk. The human evidence is limited to case series and porcine models, so I present it as a promising bridge, not a proven standard." [6]

Probing follow-up. "What if the child were ten months old?" A strong answer is: "Honey is contraindicated under twelve months because of infant botulism. I would use sucralfate 1 gram per 10 kilograms as the alternative bridge, and the two-hour removal target would still apply." [6] [7]

Common weak answer. "I will give honey and then wait to see if the battery passes." The adjunct is a bridge, never a treatment, and waiting is the classic fatal error. [1]

Escalation branch. If the candidate gives the adjunct correctly and keeps the removal target, release in Question 4 the multiple-magnet counterpoint. If they treat the adjunct as a cure, ask what the adjunct actually treats. [6] [1]

Question 4 — The multiple-magnet counterpoint

Stimulus update. The battery is removed successfully and the burn is moderate. Now a second child is referred: a well six-year-old whose radiograph shows two round densities, one in the stomach and one in the proximal jejunum, after a building-set magnet box was found open. Question: How does this differ from a single magnet, and what will and will not you do? [9]

Consultant-level model answer. "This is a high-risk multiple-magnet ingestion. Two magnets can attract across opposing bowel walls and cause fistula, perforation, obstruction, volvulus and ischaemia. The child being well does not reassure me, because the magnets can sit silently in separate loops before attracting through the walls. I will remove them if they are within endoscopic reach, with surgical standby. If they are beyond reach and the child is asymptomatic, I will observe closely with surgical standby and repeat imaging, removing them if they fail to progress or if any symptoms develop. I will not give laxatives or induce emesis, because moving magnets or raised intraluminal pressure can precipitate obstruction or bring attracting magnets into apposition." [9] [12]

Probing follow-up. "Why are laxatives harmful here?" A strong answer is: "Laxatives move the magnets unpredictably and raise intraluminal pressure, which can bring attracting magnets into apposition across bowel walls and precipitate the very obstruction and ischaemia we are trying to prevent." [9]

Common weak answer. "The child is well, so I will send them home with a laxative." A well child with two magnets is still high-risk, and laxatives are contraindicated. [12]

Escalation branch. If the candidate manages the magnets correctly, move to Question 5 on delayed complications and prevention. [9]

Question 5 — Delayed complications, safeguarding and prevention

Stimulus update. The first child is admitted after battery removal. Question: What delayed complications do you watch for, and how do you discharge and prevent? [1]

Consultant-level model answer. "The leading cause of death after button-battery ingestion is delayed great-vessel injury, classically an aorto-oesophageal fistula presenting as massive, often fatal haematemesis days to weeks after an apparently successful removal. I therefore admit for serial review of delayed perforation, fistula and stricture, arrange follow-up endoscopy, and watch for tracheo-oesophageal fistula, stricture and recurrent laryngeal nerve palsy. My safety net names chest pain, fever, haematemesis, dysphagia and abdominal pain with the route back to care. I run safeguarding when ingestion is recurrent or supervision is inadequate, and I counsel the family to secure battery compartments, keep spare batteries and magnets out of reach, and buy child-resistant packaging." [1] [6]

Probing follow-up. "What is the one principle you most want the team to carry forward?" A strong answer is: "An oesophageal button battery is removed within two hours, the honey adjunct is a bridge and never a cure, two or more magnets are high-risk even when well, and delayed complications after removal are the leading cause of death, so surveillance and prevention run in parallel with acute care." [1] [9]

Common weak answer. "The battery came out whole, so the child can go home." The injury can continue after removal, and delayed-complication surveillance is mandatory. [1]