Refeeding Syndrome Diagnosis — MRCPsych Paper B MCQ

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ModerateEating DisordersRefeeding Syndrome DiagnosisMRCPsych Paper B

An 18-year-old woman with anorexia nervosa is admitted to a medical ward for nutritional rehabilitation. Her serum phosphate, potassium and magnesium concentrations are within the local reference ranges before feeding begins. On the third day of refeeding, she develops peripheral oedema, tachycardia and confusion. Blood tests now show phosphate 0.3 mmol/L, potassium 2.9 mmol/L and magnesium 0.5 mmol/L. What is the most likely diagnosis?

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Correct answer: A — Refeeding syndrome

The correct answer is A, refeeding syndrome. Nutritional restoration after prolonged starvation produces an insulin-mediated shift of phosphate, potassium and magnesium into cells. This can cause profound hypophosphataemia, hypokalaemia and hypomagnesaemia, alongside sodium and water retention. Oedema, tachycardia and confusion are compatible clinical manifestations. The decisive features are that the electrolyte abnormalities were new and developed during refeeding, particularly the marked hypophosphataemia. Iatrogenic fluid overload may cause oedema but does not account for this characteristic biochemical pattern. Wernicke encephalopathy can cause confusion in malnutrition but does not explain the electrolyte changes or oedema. Purging can cause hypokalaemia, but marked hypophosphataemia after refeeding is more characteristic of refeeding syndrome. Pulmonary embolism does not explain the biochemical abnormalities.

Reference: Royal College of Psychiatrists. Medical Emergencies in Eating Disorders: Guidance on Recognition and Management (MEED), CR233, Chapter 4: Safe refeeding of malnourished patients with restrictive eating disorders, 2022. https://www.rcpsych.ac.uk/docs/default-source/improving-care/better-mh-policy/college-reports/college-report-cr233-medical-emergencies-in-eating-disorders-%28meed%29-guidance.pdf?sfvrsn=2d327483_55