Which statement best describes the segmental handling of potassium along the nephron?
- A Potassium is uniformly reabsorbed throughout the tubule, with secretion contributing less than 5% of urinary potassium
- B About 90% of filtered potassium is reabsorbed before the distal nephron, mostly in the proximal tubule and thick ascending limb ✓
- C Most urinary potassium derives from filtered potassium that escapes reabsorption in the loop of Henle
- D Potassium secretion occurs predominantly in the medullary collecting duct through alpha-intercalated cells
Correct answer: B. About 90% of filtered potassium is reabsorbed before the distal nephron, mostly in the proximal tubule and thick ascending limb
Explanation
Roughly 65% of filtered potassium is reabsorbed passively in the proximal tubule and another 25% in the thick ascending limb, leaving under 10% reaching the distal nephron. Nearly all urinary potassium therefore comes from active secretion by principal cells of the connecting segment and cortical collecting duct, driven by aldosterone, distal sodium delivery and tubular flow. Alpha-intercalated cells reabsorb potassium during depletion rather than secreting it.
Reference: Vander's Renal Physiology, 9th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.