A patient with kidney disease has impaired countercurrent multiplier function. What happens to urine osmolality as fluid moves through the collecting duct?

💡 Explanation

With impaired countercurrent multiplication, the medullary gradient is reduced, meaning less water is reabsorbed via osmosis from the collecting duct. Because the concentration of solutes in the urine increases as water leaves, urine osmolality rises throughout the duct; therefore, the osmolality increases, rather than decreases as it progresses.

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