Primary Polydipsia

Excerpt

Primary polydipsia (PP) is a condition where there is excess consumption of fluids leading to polyuria with diluted urine and, ultimately, hyponatremia. Polyuria can be defined as urine production greater than 40-50 ml/kg in a twenty-four-hour period. Primary polydipsia can be categorized into two types. 1) Psychogenic polydipsia and 2) Dipsogenic polydipsia. As the name suggests, psychogenic polydipsia is seen in patients with psychiatric disorders. Dipsogenic polydipsia, also called compulsory water drinking, is seen mostly in people who consciously drink large quantities of water to maintain a healthy lifestyle or in those whose hypothalamus is affected. Compulsory water drinking is perceived to improve, maintain good health, and is on the rise of late given the popularity of lifestyle programs.

This article will discuss the etiology, pathophysiology, diagnosis, and potential treatment options available for psychogenic polydipsia and dipsogenic polydipsia. Another entity to remember is beer potomania, which does not quite fit the definition of polyuria but can present with hyponatremia. This is from acute or chronic alcoholism with excessive beer drinking in patients who are typically malnourished, resulting from low solute intake/high carbohydrate intake. Psychogenic polydipsia is seen in many psychiatric conditions but is more commonly seen in schizophrenic patients. The exact mechanism is unknown, but various hypotheses have been put forward. Hyponatremia is a severe complication of primary polydipsia.

The main differential diagnosis for primary polydipsia is diabetes insipidus (DI). The diagnostic method that has been used for a long time is the indirect water deprivation test (WDT), which is an indirect measurement of the arginine vasopressin (AVP) activity, combined with the administration of desmopressin. This test differentiates primary polydipsia from diabetes insipidus and also helps differentiate central from nephrogenic diabetes insipidus. However, this traditional test is not without flaws. Various new methods have been recently proposed and are being considered as the latest diagnostic standard for the diagnoses mentioned above. These tests include copeptin measurement at baseline and after hypertonic saline infusion, the other method being the measurement of copeptin at baseline and after arginine infusion.

Regarding the treatment of this condition, there is not one particular proven strategy. The recommended treatment is to control the water intake, but this poses a compliance problem, especially in patients with psychogenic polydipsia with compulsive behavior. Changes in medications that have anticholinergic side effects can be tried. Various classes of drugs have been studied, and none is effective. Behavioral treatment trials showed mixed results. Coordination and inter-professional approach can help treat the patients better.