Tumour lysis syndrome — FFICM MCQ

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HardRenal and MetabolicTumour lysis syndromeFFICM

A 58-year-old man with high-grade lymphoma is admitted to ICU 24 hours after chemotherapy. He develops arrhythmias and oliguria. Bloods show potassium 6.4 mmol/L, phosphate 2.9 mmol/L, urate 820 micromol/L, calcium 1.82 mmol/L and creatinine 260 micromol/L. What is the most likely diagnosis?

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Correct answer: B — Tumour lysis syndrome

The correct answer is B, tumour lysis syndrome. This man developing arrhythmias, oliguria and AKI within 24 hours of chemotherapy for a high-grade lymphoma, with hyperkalaemia, hyperphosphataemia, marked hyperuricaemia and hypocalcaemia, is the classic biochemical and clinical picture of tumour lysis syndrome (TLS). TLS occurs when rapid chemotherapy-induced lysis of a large, chemosensitive tumour burden releases intracellular potassium, phosphate and nucleic acids (metabolised to urate) faster than the kidneys can excrete them, and the resulting hyperphosphataemia binds calcium, causing hypocalcaemia. High-grade lymphoma is a recognised high-risk histology for TLS, and the 24 hour post-chemotherapy timing fits the expected window (typically within 12 to 72 hours). Renal function deteriorates further as urate and calcium phosphate crystals precipitate in the renal tubules, worsening the AKI and electrolyte derangement. Why the other options are wrong: A. Refeeding syndrome: this causes hypophosphataemia, hypokalaemia and hypomagnesaemia due to insulin driven intracellular shift on reintroducing carbohydrate, the opposite electrolyte pattern to this hyperphosphataemic, hyperkalaemic picture. C. Addisonian crisis: causes hyperkalaemia and hyponatraemia from mineralocorticoid deficiency but does not explain the markedly raised urate, phosphate or the temporal link to chemotherapy. E. Diabetic ketoacidosis: there is no mention of hyperglycaemia, ketosis or acidosis, and phosphate is typically low or normal rather than elevated. D. Rhabdomyolysis alone: can raise potassium and phosphate but does not account for the markedly raised urate and does not fit the specific chemotherapy trigger described. Key point: hyperkalaemia, hyperphosphataemia, hyperuricaemia, hypocalcaemia and AKI within 12 to 72 hours of chemotherapy for a high-grade, high-turnover malignancy defines tumour lysis syndrome.

Reference: British Society for Haematology (British Committee for Standards in Haematology), Guidelines for the management of tumour lysis syndrome in adults and children with haematological malignancies, Br J Haematol 2015 (updated 2024/2025), https://onlinelibrary.wiley.com/doi/10.1111/bjh.13403