A patient with severe dehydration has impaired kidney function. Why does decreased glomerular filtration rate lead to oliguria (low urine output)?

💡 Explanation

Oliguria arises because the decreased filtration reduces the initial volume entering the nephron. Since the body retains water more efficiently due to an increased medullary osmotic gradient driving increased water reabsorption by osmosis, therefore urine output declines rather than increases as would be expected with decreased water retention mechanisms.

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