If a patient's distal convoluted tubule (DCT) becomes impermeable to water due to a genetic defect affecting aquaporin channels, which consequence follows for urine production?

💡 Explanation

An impermeable DCT prevents water reabsorption via osmosis, because the osmotic gradient created by the countercurrent multiplier cannot drive water movement across the tubule wall. Therefore, a large volume of dilute urine will be produced, rather than concentrated urine, and osmolality will decrease.

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