Psychogenic polydipsia
Encyclopedia
Primary polydipsia or psychogenic polydipsia is a special form of polydipsia
. 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.
Some forms of primary polydipsia are explicitly characterized as non-psychogenic.
, 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.
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.
is by fluid restriction. In primary polydipsia, the urine osmolality should increase and stabilize at above 280 Osm/kg. 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. A stabilization at an osmolality of less than 280 Osm/kg indicates diabetes insipidus.
, 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.
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.
Polydipsia
Polydipsia is a medical symptom in which the patient displays excessive thirst. The word derives from the Greek πολυδιψία, which is derived from πολύς + δίψα...
. 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
Phenothiazine
Phenothiazine is an organic compound that occurs in various antipsychotic and antihistaminic drugs. It has the formula S2NH. This yellow tricyclic compound is soluble in acetic acid, benzene, and ether. The compound is related to the thiazine-class of heterocyclic compounds...
medications used in some mental disorders, rather than the underlying condition.
Some forms of primary polydipsia are explicitly characterized as non-psychogenic.
Pathophysiology
The patient drinks large amounts of water, which dilutes the extracellular fluidExtracellular fluid
Extracellular fluid usually denotes all body fluid outside of cells. The remainder is called intracellular fluid.In some animals, including mammals, the extracellular fluid can be divided into two major subcompartments, interstitial fluid and blood plasma...
, decreasing its osmotic pressure
Osmotic pressure
Osmotic pressure is the pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane....
. The body responds to this by decreasing the level of vasopressin
Vasopressin
Arginine vasopressin , also known as vasopressin, argipressin or antidiuretic hormone , is a neurohypophysial hormone found in most mammals, including humans. Vasopressin is a peptide hormone that controls the reabsorption of molecules in the tubules of the kidneys by affecting the tissue's...
(antidiuretic hormone), with a resultant increased production of urine (polyuria
Polyuria
Polyuria is a condition usually defined as excessive or abnormally large production or passage of urine . Frequent urination is sometimes included by definition, but is nonetheless usually an accompanying symptom...
). 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
Cardiac arrest
Cardiac arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively...
can occur.
Diagnostic workup
The test of choice to distinguish primary polydipsia from diabetes insipidusDiabetes insipidus
Diabetes insipidus is a condition characterized by excessive thirst and excretion of large amounts of severely diluted urine, with reduction of fluid intake having no effect on the concentration of the urine. There are several different types of DI, each with a different cause...
is by fluid restriction. In primary polydipsia, the urine osmolality should increase and stabilize at above 280 Osm/kg. 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. A stabilization at an osmolality of less than 280 Osm/kg indicates diabetes insipidus.
Treatment
If the patient is institutionalisedMental Hospital
Mental hospital may refer to:*Psychiatric hospital*hospital in Nepal named Mental Hospital...
, 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 ventriclesVentricular system
The ventricular system is a set of structures containing cerebrospinal fluid in the brain. It is continuous with the central canal of the spinal cord.-Components:The system comprises four ventricles:* right and left lateral ventricles* third ventricle...
and shrunken cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
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
Psychosis
Psychosis means abnormal condition of the mind, and is a generic psychiatric term for a mental state often described as involving a "loss of contact with reality"...
, 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
Diabetes insipidus
Diabetes insipidus is a condition characterized by excessive thirst and excretion of large amounts of severely diluted urine, with reduction of fluid intake having no effect on the concentration of the urine. There are several different types of DI, each with a different cause...
, since the chronic ingestion of excessive water can produce symptoms and diagnostic results that mimic mild diabetes insipidus.
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