polyuria

Polyuria is the medical term for excessive urine production. In adults, it is commonly defined as urine output greater than about 3 liters per day, though individual thresholds may vary. Polyuria may occur with increased fluid intake (polydipsia) or reflect an underlying disorder that impairs the kidney’s ability to concentrate urine. It is often accompanied by thirst, but not always.

Common causes of polyuria include osmotic diuresis from elevated blood glucose in diabetes mellitus, and various forms of diabetes insipidus (central DI due to insufficient antidiuretic hormone, or nephrogenic DI where the kidneys do not respond to it). Other causes include the use of diuretics, certain medications such as lithium, and renal tubular disorders that reduce concentrating ability. Less common etiologies include psychogenic polydipsia, pregnancy-related changes, and chronic kidney disease in some settings.

Evaluation begins with a detailed history and physical examination, focusing on fluid intake, medications, and symptoms. Diagnostic workup typically includes measurement of 24-hour urine volume, urine osmolality, serum electrolytes, glucose, and creatinine. Additional tests may involve a water deprivation test with evaluation of vasopressin (desmopressin) response to differentiate central from nephrogenic diabetes insipidus. Imaging or more specialized tests may be indicated based on suspected causes.

Management targets the underlying condition. For osmotic diuresis, control of hyperglycemia and other contributing solutes is key. Central diabetes insipidus is treated with desmopressin; nephrogenic diabetes insipidus may respond to low-sodium diet, thiazide diuretics, and NSAIDs. Correcting electrolyte disturbances, ensuring adequate hydration, and adjusting offending medications are important components. The prognosis depends on the specific cause and its treatability.