MCQ NO 1
An 8-year-old boy with acute lymphoblastic leukemia (ALL) started chemotherapy 2 days ago. His mother reports that he has not passed urine for the last 12 hours. On examination, he is lethargic and has puffiness around the eyes. Laboratory investigations reveal:
| Investigation | Result |
|---|---|
| Serum sodium | 132 mmol/L |
| Serum potassium | 5.8 mmol/L |
| Bicarbonate | 17 mmol/L |
| Creatinine | 1.0 mg/dL |
| Phosphorus | 2.8 mmol/L |
| Calcium | 6.7 mg/dL (1.7 mmol/L) |
| Uric acid | 12.3 mg/dL (732 μmol/L) |
| Lactate dehydrogenase (LDH) | 4233 IU/L |
How can this complication be prevented?
A. Fluid restriction
B. Delaying chemotherapy
C. Intravenous hyperhydration
D. Fresh frozen plasma infusion
E. Phosphate binders
Answer: C. Intravenous hyperhydration
Explanation:
This child has developed tumor lysis syndrome (TLS), a potentially life-threatening oncologic emergency that commonly occurs in patients with acute lymphoblastic leukemia after initiation of chemotherapy. Rapid destruction of tumor cells releases intracellular contents into the bloodstream, resulting in hyperuricemia, hyperkalemia, hyperphosphatemia, hypocalcemia, and acute kidney injury.
The most effective preventive measure is intravenous hyperhydration, initiated before and continued during chemotherapy. Adequate hydration increases renal perfusion and urinary excretion of uric acid and electrolytes, reducing the risk of renal failure. High-risk patients are also given allopurinol or rasburicase as prophylaxis.
Why not the other options?
- A. Fluid restriction: Contraindicated, as it increases the risk of uric acid crystal deposition and acute kidney injury.
- B. Delaying chemotherapy: Not recommended. Appropriate prophylactic measures should be instituted before chemotherapy rather than postponing treatment.
- D. Fresh frozen plasma infusion: Has no role in the prevention of tumor lysis syndrome.
- E. Phosphate binders: May be used in the management of hyperphosphatemia but do not prevent the development of tumor lysis syndrome.
Clinical Pearl:
In a child with leukemia who develops oliguria/anuria, hyperuricemia, hyperkalemia, hyperphosphatemia, hypocalcemia, and elevated LDH shortly after chemotherapy, think of tumor lysis syndrome. Prevention includes aggressive IV hydration and uric acid–lowering therapy (allopurinol or rasburicase).