82-year-old man, with congestive hea failure and a creatinine clearance (CrCl) of 17 mL/min needs a diuretic for treatment of peripheral edema. Which of the following diuretics would be most appropriate in this patient?

The key to this question is understanding that the effectiveness of each diuretic is dependent on the creatinine clearance (CrCl). For example, the "loop" diuretics are effective down to a CrCl of around 10 mL/min. However, the thiazide and potassium-sparing diuretics are effective only down to a CrCl of around 40 mL/min. Therefore, on the basis of this patient's CrCl of 17 mL/min, only a loop diuretic would be recommended. Furosemide is a loop diuretic that is indicated for the treatment of edema associated with congestive hea failure, hepatic cirrhosis, and renal disease. Hydrochlorothiazide and indapamide are thiazide diuretics and therefore would not be recommended for patients with such a low CrCl. Spironolactone and triamterene are potassium-sparing diuretics and therefore would not be recommended for a patient with a CrCl of 17 mL/min.