Primary polydipsia
Primary polydipsia or psychogenic polydipsia is a special form of polydipsia.[1] It is usually associated with a patient's increasing fluid intake due to the sensation of having a dry mouth.
When the term "psychogenic polydipsia" is used, it implies that the condition is caused by mental disorders. However, the dry mouth is often due to phenothiazine medications used in some mental disorders, rather than the underlying condition.[2]
Some forms of primary polydipsia are explicitly characterized as non-psychogenic.[3]
Pathophysiology
The patient drinks large amounts of water, which dilutes the extracellular fluid, decreasing its osmotic pressure. The body responds to this by decreasing the level of vasopressin (antidiuretic hormone), with a resultant increased production of urine (polyuria). This urine will have a low electrolyte concentration.
Clinical presentation
Patients have been known to seek fluids from any source possible.
In extreme episodes, the patient's kidneys will be unable to deal with the fluid overload, and weight gain will be noted.
Primary polydipsia can be life threatening as serum sodium is diluted to an extent that seizures and cardiac arrest can occur.
Diagnostic workup
The test of choice to distinguish primary polydipsia from diabetes insipidus is by fluid restriction. In primary polydipsia, the urine osmolality should increase and stabilize at above 280 Osm/kg.[4] Stabilization in this test means, more specifically, when the hourly increase in osmolality is less than 30 Osm/kg per hour for at least 3 hours.[4] A stabilization at an osmolality of less than 280 Osm/kg indicates diabetes insipidus.
Treatment
If the patient is institutionalised, close monitoring by staff is necessary to control fluid intake.
In treatment-resistant polydipsic psychiatric patients, regulation in the inpatient milieu can be accomplished by use of a weight-water protocol. First, baseline weights must be established and correlated to serum sodium levels. Weight will normally fluctuate during the day, but as the water intake of the polydipsic goes up, the weight will naturally rise. The physician can order a stepped series of interventions as the weight rises. The correlation must be individualized with attention paid to the patient's normal weight and fluctuations, diet, comorbid disorders (such as a seizure disorder) and urinary system functioning. Progressive steps might include redirection, room restriction, and increasing levels of physical restraint with monitoring. Such plans should also progressive increases in monitoring, as well as a level at which a serum sodium level is drawn.
It is important to note that the majority of psychotropic drugs (and a good many of other classes) can cause dry mouth, but this is not to be confused with true polydipsia in which a dangerous drop in serum sodium will be seen.
Primary polydipsia often leads to institutionalization as it can be very difficult to manage outside the inpatient setting.
Patient profiles
Psychogenic polydipsia is a type of polydypsia described in patients with mental illnesses and/or the developmentally disabled. It is present in a subset of people with schizophrenia. These patients, most often with a long history of illness, exhibit enlarged ventricles and shrunken cortex on MRI, making the physiological mechanism difficult to isolate from the psychogenic.
While psychogenic polydipsia is usually not seen outside the population of those with serious mental disorders, it may occasionally be found among others in the absence of psychosis, although there is no extant research to document this other than anecdotal observations. Such persons typically prefer to possess bottled water that is ice cold, consume water and other fluids at excessive levels, and may be falsely diagnosed as suffering from diabetes insipidus, since the chronic ingestion of excessive water can produce symptoms and diagnostic results that mimic mild diabetes insipidus.
Veterinary Medicine
Psychogenic polydipsia is also observed in some animal patients.
Further reading
- Psychogenic polydipsia with hyponatremia: report of eleven cases. Am J Kidney Dis. 1987 May;9(5):410-6. PMID 3107377
- Risk factors for the development of hyponatremia in psychiatric inpatients. Arch Intern Med. 1995 May 8;155(9):953-7. PMID 7726704
- Efficacy of clozapine in a non-schizophrenic patient with psychogenic polydipsia and central pontine myelinolysis. Hum Psychopharmacol. 2002 Jul;17(5):253-5. PMID 12404683
See also
References
- ^ Saito T, Ishikawa S, Ito T; et al. (1999). "Urinary excretion of aquaporin-2 water channel differentiates psychogenic polydipsia from central diabetes insipidus". J. Clin. Endocrinol. Metab. 84 (6): 2235–7. doi:10.1210/jc.84.6.2235. PMID 10372737.
{{cite journal}}: Explicit use of et al. in:|author=(help); Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ Rippe, James M.; Irwin, Richard S. (2008). Irwin and Rippe's Intensive care medicine. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. p. 909. ISBN 0-7817-9153-7.
{{cite book}}: CS1 maint: multiple names: authors list (link) - ^ Tobin MV, Morris AI (1988). "Non-psychogenic primary polydipsia in autoimmune chronic active hepatitis with severe hyperglobulinaemia". Gut. 29 (4): 548–9. doi:10.1136/gut.29.4.548. PMC 1433532. PMID 3371724.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ a b Elizabeth D Agabegi; Agabegi, Steven S. (2008). Step-Up to Medicine (Step-Up Series). Hagerstwon, MD: Lippincott Williams & Wilkins. ISBN 0-7817-7153-6.
{{cite book}}: CS1 maint: multiple names: authors list (link)