A 34-year-old woman visits her doctor complaining of frequent urination. She attempted to limit her fluid intake but found it difficult because she became extremely thirsty. The doctor evaluates her kidneys' water-saving function by administering a water restriction test, which reveals excessively dilute urine. Low vasopressin levels have been found in laboratory studies conducted during a period of water deprivation. The doctor diagnoses the patient with central diabetes insipidus and explains that her kidneys are unable to absorb enough water due to faulty hormone production. Which of the following nephron areas is normally water-impermeable regardless of serum vasopressin levels?

Question

Quizplus · Accepted Answer

Eductional Objective: Regardless of serum vasopressin levels, the ascending limb of the loop of Henle is impermeable to water. The Na+/K+/2Cl- cotransporter absorbs electrolytes in the thick ascending limb, contributing to the formation of the corticomedullary concentration gradient.

A 34-Year-Old Woman Visits Her Doctor Complaining of Frequent Urination