A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
A 60-year-old man comes to the physician because of a 2-day history of blood in his urine, lower abdominal pain, and a burning sensation while micturating. Five months ago, he was diagnosed with high-grade non-Hodgkin lymphoma and a deep vein thrombosis of his right popliteal vein. His medications include polychemotherapy every 3 weeks and a daily subcutaneous dose of low molecular weight heparin. The last cycle of chemotherapy was 2 weeks ago. His temperature is 37°C (98.6°F), pulse is 94/min, and blood pressure is 110/76 mm Hg. Examination shows bilateral axillary and inguinal lymphadenopathy, hepatosplenomegaly, and mild suprapubic tenderness. Laboratory studies show:
Hemoglobin 10.2 g/dL
Leukocytes 4,300/mm3
Platelet count 145,000/mm3
Partial thromboplastin time 55 seconds
Prothrombin time 11 seconds (INR=1)
Urine
RBCs 50–55/hpf
RBC casts negative
WBCs 7/hpf
Epithelial cells 5/hpf
Bacteria occasional
Administration of which of the following is most likely to have prevented this patient's current condition?"
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A
Protamine sulfateIncorrect. Protamine sulfate reverses heparin; while the patient has elevated PTT on LMWH, the bleeding here is bladder-source from chemotherapy, not anticoagulant excess.
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B
Mercaptoethane sulfonateCorrect. MESNA (mercaptoethane sulfonate) binds the toxic metabolite acrolein in the bladder, preventing cyclophosphamide-induced hemorrhagic cystitis.
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C
CiprofloxacinIncorrect. Ciprofloxacin treats bacterial UTI; the urinalysis here shows minimal bacteria with heavy RBC count, more consistent with hemorrhagic cystitis from chemo than infection.
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D
DexrazoxaneIncorrect. Dexrazoxane is a cardioprotectant against doxorubicin-induced cardiotoxicity — it doesn't protect the bladder from cyclophosphamide metabolites.
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E
AllopurinolIncorrect. Allopurinol prevents tumor lysis syndrome by reducing uric acid production; it doesn't protect the bladder mucosa from acrolein-mediated cyclophosphamide toxicity.
↑ Tap an answer to reveal the reasoning
Answer: B. This patient with non-Hodgkin lymphoma receiving polychemotherapy now has hematuria and dysuria with suprapubic tenderness — classic hemorrhagic cystitis from cyclophosphamide (an alkylating agent used in many lymphoma regimens like CHOP). The toxic metabolite is acrolein, formed when cyclophosphamide is broken down; acrolein concentrates in the bladder and damages the urothelium, producing hemorrhagic inflammation.
The prophylaxis (and treatment) is MESNA — sodium 2-mercaptoethane sulfonate (mercaptoethane sulfonate). MESNA contains a free thiol group that binds acrolein in the bladder, neutralizing it before it can damage the urothelium. MESNA is given concurrently with cyclophosphamide or ifosfamide to prevent hemorrhagic cystitis, along with adequate hydration.
Protamine sulfate reverses heparin — not useful here. Ciprofloxacin treats bacterial UTI but the urine shows only occasional bacteria with negative casts and elevated PTT (likely from heparin), suggesting hemorrhagic cystitis from chemo rather than bacterial UTI. Dexrazoxane is a cardioprotectant against doxorubicin-induced cardiotoxicity (chelates iron, reduces reactive oxygen species in cardiomyocytes) — not useful for bladder protection. MESNA is the right answer.
**Why each option:**
**A.** Protamine sulfate reverses heparin; while the patient has elevated PTT on LMWH, the bleeding here is bladder-source from chemotherapy, not anticoagulant excess.
**B.** Correct. MESNA (mercaptoethane sulfonate) binds the toxic metabolite acrolein in the bladder, preventing cyclophosphamide-induced hemorrhagic cystitis.
**C.** Ciprofloxacin treats bacterial UTI; the urinalysis here shows minimal bacteria with heavy RBC count, more consistent with hemorrhagic cystitis from chemo than infection.
**D.** Dexrazoxane is a cardioprotectant against doxorubicin-induced cardiotoxicity — it doesn't protect the bladder from cyclophosphamide metabolites.