Acute liver failure: Viva

Branch 1: Diagnosis and the paediatric definition

The candidate should recognise that this boy has acute liver failure. The combination of an international normalised ratio of 3.8 with borderline drowsiness, in a previously well adolescent without known chronic liver disease, meets the paediatric definition, and the low ceruloplasmin and Kayser-Fleischer rings make Wilson disease the leading cause. A strong candidate states the definition precisely: an international normalised ratio of 1.5 or greater with any hepatic encephalopathy, or 2.0 or greater without encephalopathy, in a child without chronic liver disease. ^[1]

The candidate should emphasise the key paediatric distinction that hepatic encephalopathy is not required for the diagnosis, unlike in adults, because infants and young children may not show recognisable encephalopathy until late. In this adolescent the borderline drowsiness is early encephalopathy, but even without it the international normalised ratio of 3.8 alone would confirm the diagnosis. The candidate should also distinguish this from acute-on-chronic failure: although Wilson disease is a chronic condition, this presentation is an acute decompensation in a previously undiagnosed child, which is a classic acute liver failure scenario rather than acute-on-chronic failure of a known disease. ^[1]

If the examiner presses on Wilson disease, the candidate should describe the nearly pathognomonic combination of Coombs-negative haemolytic anaemia, a low or normal alkaline phosphatase relative to the bilirubin, and acute liver failure, often with Kayser-Fleischer rings on slit-lamp examination. The low alkaline phosphatase-to-bilirubin ratio is a bedside clue, and a 24-hour urinary copper or a serum free copper level confirms the diagnosis. ^[2]