Polyuria

Polyuria is a condition usually defined as excessive or abnormally large production or passage of urine (greater than 2.5 or 3 L over 24 hours in adults). Frequent urination is sometimes included by definition but is nonetheless usually an accompanying symptom. Increased production and passage of urine may also be termed diuresis. Polyuria often appears in conjunction with polydipsia (increased thirst), though it is possible to have one without the other, and the latter may be a cause or an effect. Psychogenic polydipsia may lead to polyuria.

Causes

The most common cause of polyuria in both adults and children is uncontrolled diabetes mellitus, which causes osmotic diuresis, when glucose levels are so high that glucose is excreted in the urine. Water follows the glucose concentration passively, leading to abnormally high urine output. In the absence of diabetes mellitus, the most common causes are decreased secretion of aldosterone due to adrenal cortical tumor, primary polydipsia (excessive fluid drinking), central diabetes insipidus and nephrogenic diabetes insipidus. Polyuria may also be due to various chemical substances, such as diuretics, caffeine, and ethanol. It may also occur after supraventricular tachycardias, during an onset of atrial fibrillation, childbirth, and the removal of an obstruction within the urinary tract. Diuresis is controlled by antidiuretics such as vasopressin, angiotensin II and aldosterone. Cold diuresis is the occurrence of increased urine production on exposure to cold, which also partially explains immersion diuresis. High-altitude diuresis occurs at altitudes above 10,000 feet (3,000 m) and is a desirable indicator of adaptation to high altitudes. Mountaineers who are adapting well to high altitudes experience this type of diuresis. Persons who produce less urine even in the presence of adequate fluid intake are probably not adapting well to altitude.