A 58-year-old man with chronic kidney disease (eGFR 35 mL/min/1.73m²) and hypertension presents with peripheral edema and dyspnea. He is already on lisinopril and amlodipine. Which diuretic is the drug of choice for managing his volume overload?

Explanation

## Diuretic Selection in CKD with Volume Overload **Key Point:** Loop diuretics are the first-line agents for managing volume overload in patients with reduced GFR (eGFR <45 mL/min/1.73m²) because they maintain efficacy despite impaired renal function. ### Why Furosemide is Correct Furosemide is a loop diuretic that: - Remains effective at low GFR (works by secretion into the proximal tubule lumen) - Produces potent natriuresis and diuresis, essential for symptomatic relief in CKD - Does not accumulate to toxic levels in renal impairment - Is the standard agent for edema and dyspnea in advanced CKD **Clinical Pearl:** Loop diuretics work even when creatinine clearance is severely reduced because they are actively secreted into the tubular lumen via organic anion transporters, bypassing glomerular filtration. ### Comparison with Other Agents | Agent | GFR Threshold | Efficacy in CKD | Use in This Case | |-------|---------------|-----------------|------------------| | **Furosemide (Loop)** | Works at any GFR | Maintained | ✓ **First-line** | | **Hydrochlorothiazide (Thiazide)** | Needs GFR >30 | Lost at GFR <30 | ✗ Ineffective here | | **Spironolactone (K-sparing)** | Any GFR | Maintained | ✗ Risk of hyperkalemia in CKD | | **Mannitol (Osmotic)** | Any GFR | Maintained | ✗ Reserved for acute cerebral edema/IOP | **High-Yield:** In CKD with eGFR 35, thiazides lose efficacy; loop diuretics remain the workhorse. Potassium-sparing agents are avoided due to hyperkalemia risk in reduced renal function. **Warning:** Do not use thiazides as monotherapy in advanced CKD — they become ineffective and may worsen metabolic abnormalities (hyperglycemia, hyperuricemia).