A 52-year-old man with chronic kidney disease (eGFR 35 mL/min/1.73m²) and hypertension presents with ankle edema and breathlessness. He is already on lisinopril and amlodipine. Which diuretic is the drug of choice for managing his fluid overload?

Explanation

## Clinical Context The patient has moderate-to-advanced CKD with volume overload (edema, breathlessness). Loop diuretics are the preferred choice in this scenario because they: 1. Remain effective even at reduced GFR (glomerular filtration rate) 2. Produce more potent natriuresis and diuresis than thiazides 3. Are the only diuretics reliably effective when eGFR < 30 mL/min/1.73m² ## Why Furosemide is First-Line Here **Key Point:** Loop diuretics (furosemide, torsemide, bumetanide) are the preferred agents for volume overload in CKD because they work via active secretion into the proximal tubule lumen, independent of GFR. **High-Yield:** Furosemide is the most commonly used loop diuretic in India and globally. It is effective even in advanced renal disease and produces rapid onset of action (1 hour oral, 5 minutes IV). **Clinical Pearl:** In CKD, thiazide diuretics lose efficacy when eGFR falls below 30 mL/min/1.73m², making loop diuretics mandatory. The patient's eGFR of 35 is borderline; furosemide is safer and more reliable. ## Mechanism Furosemide inhibits the Na⁺-K⁺-2Cl⁻ cotransporter in the thick ascending limb of the loop of Henle, blocking ~25% of filtered sodium reabsorption — the most potent site of action among all diuretics. ## Dosing in CKD - Start: 40 mg once or twice daily - Titrate based on response (may need higher doses in advanced CKD) - Monitor: serum creatinine, potassium, uric acid ## Comparison with Other Options | Diuretic | Mechanism | Efficacy in CKD | Use in This Case | |---|---|---|---| | **Furosemide** | Loop (Na⁺-K⁺-2Cl⁻ inhibitor) | Excellent (eGFR any level) | **First-line** | | Hydrochlorothiazide | Thiazide (distal convoluted tubule) | Poor (eGFR < 30) | Contraindicated | | Spironolactone | K⁺-sparing (aldosterone antagonist) | Moderate; **hyperkalemia risk** | Avoid in CKD without close monitoring | | Mannitol | Osmotic | Ineffective in CKD; **nephrotoxic** | Contraindicated | **Warning:** Spironolactone is contraindicated in moderate-to-advanced CKD due to high risk of hyperkalemia, especially when combined with ACE inhibitor (lisinopril). Mannitol is nephrotoxic and worsens renal function.