In a patient with diffuse large B‑cell lymphoma receiving B‑CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone) who develops anuric renal failure with hyperkalemia, hypocalcemia, and hyperphosphatemia, what is the most appropriate next step in management in addition to aggressive intravenous hydration?

Management of Tumor Lysis Syndrome with Anuric Renal Failure

Rasburicase (Option C) is the most appropriate next step in addition to hydration for this patient with clinical tumor lysis syndrome presenting with anuric renal failure, hyperkalemia (6 mmol/L), hypocalcemia, and hyperphosphatemia. 1, 2, 3, 4

Clinical Reasoning

This patient has clinical tumor lysis syndrome (TLS), defined by the presence of at least 2 metabolic abnormalities (hyperkalemia, hyperphosphatemia, hypocalcemia) plus renal failure—even without documented hyperuricemia. 1, 4 The European Hematology Association explicitly states that laboratory TLS requires only 2 of 4 metabolic derangements (hyperkalemia, hyperphosphatemia, hypocalcemia, or hyperuricemia—not necessarily hyperuricemia alone), and treatment of laboratory TLS is identical to clinical TLS. 1, 4

Why Rasburicase is the Correct Answer

• Rasburicase should be administered to all patients with clinical TLS regardless of which specific metabolic abnormalities are present or whether uric acid is documented. 2, 3, 4 The consensus guidelines state that hydration plus rasburicase should be given to all adults with laboratory or clinical TLS. 1

• Administer rasburicase 0.2 mg/kg IV over 30 minutes immediately, continuing daily for 3-5 days. 1, 2, 5 This enzymatically converts existing uric acid to allantoin (5-10 times more soluble), providing immediate reduction of hyperuricemia and preventing further uric acid crystal deposition in renal tubules. 2, 6

• Rasburicase is superior to allopurinol in high-risk TLS because it degrades pre-existing uric acid rather than merely preventing new formation, achieving significantly lower uric acid levels (mean area under curve 128±70 vs 329±129 mg/dL/hour, p<0.001). 1, 2

Why the Other Options are Incorrect

Loop Diuretics (Lasix - Option A) are Contraindicated

• Loop diuretics are explicitly contraindicated in patients with anuria or oliguria despite adequate hydration. 1, 3 The guidelines state that loop diuretics may be used to maintain urine output of ≥100 mL/hour, except in patients with concomitant obstructive uropathy or hypovolemia—and this patient is anuric despite hydration. 1, 2

• This patient requires urgent hemodialysis, not diuretics. 3 The American Society of Nephrology recommends initiating hemodialysis urgently when oliguria or anuria develops despite aggressive hydration. 3

Thiazide Diuretics (Option B) Have No Role

• Thiazide diuretics are not mentioned in any TLS management guideline and would be ineffective in anuric renal failure. 1, 2, 3

• Thiazides work at the distal convoluted tubule and require functioning nephrons—this patient has complete renal shutdown. 3

Prednisone (Option D) is Already Being Given

• Prednisone is a component of the R-CHOP regimen this patient is already receiving (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone). 7, 8

• Additional prednisone has no role in acute TLS management beyond what is already included in the chemotherapy protocol. 1, 2

Concurrent Management of Severe Hyperkalemia

While rasburicase is the answer to the question, this patient's potassium of 6 mmol/L requires immediate concurrent treatment:

• For severe hyperkalemia (≥6 mmol/L), administer rapid insulin 0.1 units/kg IV plus 25% dextrose 2 mL/kg IV, calcium gluconate 50-100 mg/kg IV to stabilize myocardial membrane, and sodium bicarbonate to correct acidosis. 1, 2, 3

• Continuous ECG monitoring is mandatory to detect life-threatening arrhythmias. 1, 3

• Sodium polystyrene sulfonate 1 g/kg orally or by enema can be added for potassium removal. 1, 3

Critical Pitfalls to Avoid

• Never delay rasburicase waiting for uric acid results—clinical TLS with renal failure is an indication regardless of uric acid level. 2, 3, 4

• Do not treat asymptomatic hypocalcemia in the presence of hyperphosphatemia, as calcium administration can cause metastatic calcification and worsen renal function. 1, 2, 3 Only treat if tetany, seizures, or prolonged QT develops. 1, 3

• Do not alkalinize urine when using rasburicase—this increases calcium-phosphate precipitation risk without benefit since rasburicase rapidly degrades uric acid. 2, 3

• Screen for G6PD deficiency before rasburicase in high-risk populations (African or Mediterranean ancestry), as rasburicase is absolutely contraindicated in G6PD deficiency due to risk of severe hemolysis. 1, 5

Dialysis Planning

• This patient will likely require urgent hemodialysis given anuria despite hydration and severe hyperkalemia. 3 Indications include severe oliguria/anuria, persistent hyperkalemia ≥6 mmol/L unresponsive to medical management, hyperphosphatemia with symptomatic hypocalcemia, and severe volume overload. 2, 3

• Hemodialysis can reduce plasma uric acid by approximately 50% with each 6-hour treatment. 2