Why does the osmolarity gradient in the kidney medulla diminish with insufficient ADH despite a functioning countercurrent multiplier?

💡 Explanation

The medullary osmotic gradient relies on slow blood flow through the vasa recta to prevent solute washout. Insufficient ADH leads to increased medullary blood flow, disrupting the countercurrent exchange, because the solutes are carried away faster than they can be reabsorbed; therefore, the gradient diminishes, rather than being maintained by the countercurrent multiplier.

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