A 71-year-old woman visits the office for a check-up. She has a history of systolic heart failure and was admitted to the hospital two weeks ago for an exacerbation that was treated with intravenous diuretics. The patient has been taking oral diuretics since her discharge and reports that her shortness of breath has improved, but she is now experiencing muscle weakness and cramping. The blood pressure is 128/72 mm Hg, and the pulse rate is 80 beats per minute. A physical examination reveals that the lower extremities have mildly decreased muscle strength. A serum potassium level of 2.2 mEq/L is determined by laboratory testing. The patient is given potassium supplements, which help with his weakness. Another diuretic is added to her treatment plan to help prevent this side effect in the future. This additional medication predominantly acts on which of the following nephron segments?

Question

Quizplus · Accepted Answer

Eductional Objective: Except for potassium-sparing diuretics, all diuretics cause potassium loss by increasing sodium delivery to the late distal tubule and cortical collecting duct, where aldosterone-induced sodium reabsorption takes place at the expense of potassium. To counteract the effects of aldosterone, potassium-sparing diuretics (e.g., spironolactone, amiloride) act on the late distal tubule and cortical collecting duct.

A 71-Year-Old Woman Visits the Office for a Check-Up