Referring to urinary excretion in excess of 3 quarts (appx. 2.8 liters), polyuria typically results from hyperglycemia, conditions causing nocturnal polyuria and drinking large amounts of water, which is the most obvious. Taking certain medications, especially those ordered for high blood pressure, also increase the output of urine. Save for excessive water drinking, the common causes of polyuria can be linked to several abnormal conditions occurring within the body — either there is a critical reduction in the antidiuretic hormone (ADH) response or in the amount of ADH released. It is also associated with urinary excretion of solutes such as glucose and salt. Polyuria is found most in those with diabetes mellitus that has not been managed and in the elderly population.
Hyperglycemia, the condition of having excessive sugar within the blood, ends in polyuria. This is brought about by the altered functioning of the kidneys as they attempt to handle the large amounts of glucose for its return to the body. In lieu, the kidneys fail at filtering it as there aren't enough proteins available to move all of the glucose out of the kidneys, eventually leading to excretion of glucose in the urine. The reason this happens has to do with the fact that sugar, like salt, concentrates the urine, pulling water in to dilute its concentration as water flows from an area of higher water concentration to one that is lower. Often an earlier indication of diabetes insipidus and mellitus, causes of polyuria include polydipsia, a notable thirst leading to increased amounts of excreted urine.
Characterized by tiredness, edema of the lower extremities, and breathing difficulties, congestive heart failure is included in the causes of polyuria, particularly at night. Etiology of increased production of urine at night in the case of congestive heart failure involves the inability of the heart to efficiently move blood throughout systemic circulation, which causes fluid to build up in places like the abdomen and ankles. At night during sleep, the body attempts to reabsorb fluid, releasing large amounts of urine. Nocturnal polyuria tends to affect the elderly population.
Determined to be one of the causes of polyuria, the metabolism of certain drugs leads to increased urinary output. Used in the treatment of hypertension, diuretics work to lower blood pressure via urination. Salt is excreted along with the urine as directed by the kidneys and, because there is less water volume within blood, the pressure is thereby decreased. Other drugs having polyuria as a result include metronidazole, which is provided for trichomoniasis, as well as antihistamines such as chlorpheniramine maleate.