A 34-year-old woman comes to the physician complaining of frequent urination. She has tried limiting her fluid intake but found it difficult because she got very thirsty. The physician assesses the water-conserving function of her kidneys by performing a water restriction test, which shows inappropriately dilute urine. Laboratory studies drawn during the period of water deprivation show low vasopressin levels. The physician diagnoses the patient with central diabetes insipidus and explains that her kidneys are unable to absorb the proper amount of water due to defective hormone production. Which of the following areas of the nephron is normally impermeable to water regardless of serum vasopressin levels?

Question

A 34-year-old woman comes to the physician complaining of frequent urination.  She has tried limiting her fluid intake but found it difficult because she got very thirsty.  The physician assesses the water-conserving function of her kidneys by performing a water restriction test, which shows inappropriately dilute urine.  Laboratory studies drawn during the period of water deprivation show low vasopressin levels.  The physician diagnoses the patient with central diabetes insipidus and explains that her kidneys are unable to absorb the proper amount of water due to defective hormone production.  Which of the following areas of the nephron is normally impermeable to water regardless of serum vasopressin levels?

Quizplus · Accepted Answer

11ec160b_3cef_9c14_9249_bf5df20e2981_MD0001_00 Free water excretion by the kidney depends primarily on serum vasopressin (antidiuretic hormone) levels. This hormone acts on the nephron to regulate the osmotic pressure of body fluids by varying the water permeability of the distal portion of the nephron. Water and electrolyte permeability varies in different regions of the nephron as follows: Educational objective: The ascending limb of the loop of Henle is impermeable to water regardless of serum vasopressin levels. Reabsorption of electrolytes by the Na⁺/K⁺/2Cl^- cotransporter occurs in the thick ascending limb and contributes to formation of the corticomedullary concentration gradient.

A 34-Year-Old Woman Comes to the Physician Complaining of Frequent