Examqo › Examqo library › Oncology › Oncologic emergencies · IMLE
Tumour lysis syndrome
Rapid breakdown of tumour cells releases potassium, phosphate and nucleic acids (which become uric acid) — the kidneys are injured and there is a danger of arrhythmia; prevention with hydration and allopurinol or rasburicase by risk is the most important treatment.
Why it matters in the exam
The syndrome is asked in almost every exam, in oncology and internal medicine. The typical scenario is a patient with bulky lymphoma or leukaemia with a high count who, a few days after starting treatment, develops renal failure, high potassium and low calcium. The question tests recognition, prevention and correct treatment.
Recurring points: rasburicase breaks down existing uric acid but is forbidden in G6PD deficiency; allopurinol prevents new uric acid formation but does not lower existing uric acid; urine is not alkalinised; and asymptomatic low calcium is not corrected, because this increases calcium-phosphate deposition in tissues. Solid tumours and newer treatments such as venetoclax can also cause the syndrome.
Key points
- Tumour lysis syndrome includes high uric acid, potassium and phosphate and low calcium, and occurs mainly in fast and bulky tumours.
- The main dangers are renal failure and arrhythmia from high potassium, so prevention starts before treatment.
- At intermediate risk hydration and allopurinol are given, and at high risk hydration and rasburicase.
- Rasburicase is forbidden in G6PD deficiency, and allopurinol does not lower uric acid that has already formed.
- Urine is not alkalinised, and asymptomatic low calcium is not corrected, so as not to increase calcium-phosphate deposition.
Summary table
| Issue | What to know | Exam detail |
|---|---|---|
| High-risk tumours | Burkitt lymphoma, acute leukaemia with a high count, bulky diffuse large cell lymphoma | Rare in solid tumours — small cell, germ cell; venetoclax in CLL |
| Laboratory | High uric acid, potassium and phosphate; low calcium (secondary to phosphate) | Laboratory definition: 2 or more abnormal values from 3 days before to 7 days after treatment |
| Clinical syndrome | The laboratory definition plus kidney injury, arrhythmia, seizure or death | Kidney injury from uric acid crystals and calcium-phosphate deposits |
| Prevention at intermediate risk | Hydration and allopurinol | Allopurinol inhibits xanthine oxidase — prevents formation, does not lower existing uric acid |
| Prevention at high risk or established syndrome | Hydration and rasburicase | Rasburicase turns uric acid into allantoin; forbidden in G6PD deficiency (haemolysis and methaemoglobinaemia) |
| Electrolyte treatment | High potassium — immediate treatment by protocol; low calcium — treat only when symptomatic | No urine alkalinisation — it increases calcium-phosphate deposition |
| Dialysis | Refractory potassium or phosphate, fluid overload or advanced renal failure | An early decision, together with a nephrologist |
In the full version for subscribers
- A simple algorithm
- Memory aid
- Exam traps
- 5 review cards
- Enough for IMLE
The full version is open to subscribers of: Oncology, Internal medicine, Emergency medicine, Medical licensing exam (IMLE).
Subscriber? Read the full topic Plans and prices 25 free questions
Sources
- Cairo and Bishop, Tumour lysis syndrome: new therapeutic strategies and classification, British Journal of Haematology, 2004 — Definitions
- Howard, Jones and Pui, The tumor lysis syndrome, New England Journal of Medicine, 2011 — Prevention and management
- NCCN Clinical Practice Guidelines in Oncology: B-Cell Lymphomas, 2026 — Supportive care: tumor lysis syndrome
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.