Abdominal radiograph and acute imaging decisions — branching viva

Opening branch — the imaging decision for suspected appendicitis

The candidate is expected to define the clinical question (is this appendicitis?), to state that ultrasound is the first-line imaging modality because it uses no ionising radiation, and to explain that the abdominal radiograph has a very low yield and is not the appropriate first test. [3]

The examiner probes the pARC calculator, which stratifies the probability of appendicitis from the age, the sex, the pain duration and migration, the right-lower-quadrant tenderness, the guarding, the rebound, the anorexia, and the nausea. The high-probability child proceeds to surgical review, the intermediate-probability child has the ultrasound as the deciding test, and the low-probability child is observed or discharged with a safety net. [4]

Second branch — the equivocal ultrasound and the computed tomography decision

The examiner presents the equivocal ultrasound, with a non-compressible structure that may or may not be the appendix. The candidate is expected to state that computed tomography is the appropriate next step when the ultrasound is equivocal and the clinical concern persists, and to apply the ALARA principle: the dose is modified to the size of the child, the region is limited to the question, and the intravenous contrast is used when the soft-tissue detail is needed. [2][3]

The examiner probes the Pearce 2012 evidence that the childhood computed tomography carries a small increase in the leukaemia and brain tumour risk with the cumulative dose, and the Image Gently campaign that translates the evidence into the dose-optimisation and the justification practice. [1][2]

Third branch — the infant with bilious vomiting

The examiner shifts to the 5-week-old infant with bilious (green) vomiting. The candidate is expected to recognise the malrotation with midgut volvulus as the diagnosis to exclude, to state that the upper gastrointestinal contrast study demonstrating the abnormal duodenojejunal flexure is the definitive test, and to explain that the bilious vomit in the infant is a surgical emergency because the bowel can infarct within hours. [6]

The examiner probes the consequence of the delay (short bowel syndrome, lifelong parenteral nutrition dependence, death) and the principle that the green vomit in the infant is the malrotation and the volvulus until the contrast study proves otherwise. [6]

Fourth branch — the suspected button battery ingestion

The examiner shifts to the 2-year-old with a suspected button battery ingestion. The candidate is expected to state that the abdominal radiograph is the single most useful test because it localises the battery, and that the double-ring or the halo sign distinguishes the button battery from the uniform disc of the coin. The battery lodged in the oesophagus is the emergency, because it can perforate into the aorta or the trachea within hours, and the urgent endoscopic removal is the management. [7]

The examiner probes the management of the gastric battery, which is observed or removed depending on the size and the symptoms, and the principle that every suspected button battery ingestion gets the radiograph. [7]

Closing — the radiation-aware practice

The examiner closes by asking the candidate to summarise the radiation-aware imaging practice in the acute paediatric abdomen. The expected answer is the modality match (ultrasound first, radiograph for the perforation, obstruction, and foreign body, contrast study for the malrotation, computed tomography for the equivocal or the unstable), the ALARA principle, and the ASK framework that the lowest-dose modality is chosen, the specific question is stated, and every computed tomography scan is justified. [1][2]