Which condition would typically show a concentrated urine (high specific gravity)?

Which condition would typically show a concentrated urine (high specific gravity)?

• A. SIADH
• B. Diabetes Insipidus
• C. Hyperaldosteronism
• D. Renal Calculi

Answer: (A)

High urine concentration happens when ADH is acting on the kidneys to reabsorb water in the collecting ducts. In SIADH, ADH is released inappropriately, so the kidneys keep reabsorbing water even when plasma osmolality is low. That leads to a concentrated urine with a high urine specific gravity and high urine osmolality, along with dilutional hyponatremia. Diabetes insipidus, by contrast, involves not enough ADH or kidney insensitivity to it, so the urine is dilute and the specific gravity is low. Renal aldosterone excess and renal calculi don’t routinely produce the pattern of persistently concentrated urine seen with SIADH, so they aren’t the classic matches for high urine specific gravity.

High urine concentration happens when ADH is acting on the kidneys to reabsorb water in the collecting ducts. In SIADH, ADH is released inappropriately, so the kidneys keep reabsorbing water even when plasma osmolality is low. That leads to a concentrated urine with a high urine specific gravity and high urine osmolality, along with dilutional hyponatremia.

Diabetes insipidus, by contrast, involves not enough ADH or kidney insensitivity to it, so the urine is dilute and the specific gravity is low.

Renal aldosterone excess and renal calculi don’t routinely produce the pattern of persistently concentrated urine seen with SIADH, so they aren’t the classic matches for high urine specific gravity.