A middle-aged man is evaluated for polydipsia and polyuria. His 24-hour urine volume is 7.0 L with a low osmolality, and is negative for red blood cells, leukocytes, protein, and glucose. His blood pressure and heart rate are both normal. Which of the following is a likely cause of polyuria in this patient?
A) Acute attack of diabetes mellitus without glucosuria
B) Acute renal failure with a severe decrease in glomerular filtration rate (GFR)
C) Cerebrovascular accident damaging the anterior pituitary gland
D) Renal supersensitivity to the effects of antidiuretic hormone (ADH)
E) Suppression of ADH secretion due to polydipsia

Question

Quizplus · Accepted Answer

The patient's symptoms of polydipsia (excessive thirst) and polyuria (excessive urination) along with a low urine osmolality and absence of glucose, protein, or blood cells in the urine suggest a diagnosis related to an issue with water balance rather than a primary kidney or glucose handling problem. Suppression of ADH (antidiuretic hormone) secretion due to polydipsia is a likely cause, as excessive intake of water can lead to a decrease in ADH secretion, resulting in the production of a large volume of dilute urine.

A Middle-Aged Man Is Evaluated for Polydipsia and Polyuria