Polydipsia
Encyclopedia
Polydipsia is a medical symptom in which the patient displays excessive thirst
. The word derives from the Greek
πολυδιψία, which is derived from πολύς (polys, "much, many") + δίψα (dipsa, "thirst"). An etymologically related term is dipsomaniac, meaning an alcoholic.
, often as one of the initial symptoms, and in those who fail to take their anti-diabetic medications or whose dosages have become inadequate. It can also be caused by a change in the osmolality of the extracellular fluid
s of the body, hypokalemia
, decreased blood volume
(as occurs during major hemorrhage), and other conditions that create a water deficit. This is usually a result of osmotic diuresis
. Diabetes insipidus
("tasteless" diabetes, as opposed to diabetes mellitus) can also cause polydipsia. Polydipsia is also a symptom of anticholinergic
poisoning. Zinc is also known to reduce symptoms of polydipsia by causing the body to absorb fluids more efficiently (reduction of diarrhea, induces constipation) and it causes the body to retain more sodium; thus a zinc deficiency can be a possible cause.
, and/or the developmentally disabled. It should be taken very seriously, as the amount of water ingested exceeds the amount that can be excreted by the kidneys, and can on rare occasions be life-threatening as the body's serum sodium level is diluted to an extent that seizures and cardiac arrest can occur.
While psychogenic polydipsia is generally not found outside the population of serious mental disorders, there is some anecdotal evidence of a milder form (typically called 'habit polydipsia' or 'habit drinking') that can be found in the absence of psychosis or other mental conditions. The excessive levels of fluid intake may result in a false diagnosis of diabetes insipidus
, since the chronic ingestion of excessive water can produce diagnostic results that closely mimic those of mild diabetes insipidus. As discussed in the entry on diabetes insipidus
, "Habit drinking (in its severest form termed psychogenic polydipsia) is the most common imitator of diabetes insipidus at all ages. While many adult cases in the medical literature are associated with mental disorders, most patients with habit polydipsia have no other detectable disease. The distinction is made during the water deprivation test, as some degree of urinary concentration above isosmolar is usually obtained before the patient becomes dehydrated." However, prior to a water deprivation test, consideration should be given to a psychiatric consult to see whether it is possible to rule out psychogenic polydipsia or habit polydipsia.
, investigations directed at diagnosing diabetes insipidus
and diabetes mellitus
can be useful. Blood serum tests can also provide useful information about the osmolality of the body's extracellular fluids. A decrease in osmolality caused by excess water intake will decrease the serum concentration of red blood cells
, blood urea nitrogen
(BUN), and sodium.
Thirst
Thirst is the craving for fluids, resulting in the basic instinct of animals to drink. It is an essential mechanism involved in fluid balance. It arises from a lack of fluids and/or an increase in the concentration of certain osmolites, such as salt...
. The word derives from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
πολυδιψία, which is derived from πολύς (polys, "much, many") + δίψα (dipsa, "thirst"). An etymologically related term is dipsomaniac, meaning an alcoholic.
Causes
This symptom is characteristically found in diabeticsDiabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
, often as one of the initial symptoms, and in those who fail to take their anti-diabetic medications or whose dosages have become inadequate. It can also be caused by a change in the osmolality of the extracellular fluid
Extracellular 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...
s of the body, hypokalemia
Hypokalemia
Hypokalemia or hypokalaemia , also hypopotassemia or hypopotassaemia , refers to the condition in which the concentration of potassium in the blood is low...
, decreased blood volume
Blood volume
Blood volume is the volume of blood in the circulatory system of an individual.-Humans:A typical adult has a blood volume of approximately between 4.7 and 5 liters, with females generally having less blood volume than males....
(as occurs during major hemorrhage), and other conditions that create a water deficit. This is usually a result of osmotic diuresis
Osmotic diuresis
Osmotic diuresis is increased urination caused by the presence of certain substances in the small tubes of the kidneys. The excretion occurs when substances such as glucose enter the kidney tubules and cannot be reabsorbed...
. 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...
("tasteless" diabetes, as opposed to diabetes mellitus) can also cause polydipsia. Polydipsia is also a symptom of anticholinergic
Anticholinergic
An anticholinergic agent is a substance that blocks the neurotransmitter acetylcholine in the central and the peripheral nervous system. An example of an anticholinergic is dicycloverine, and the classic example is atropine....
poisoning. Zinc is also known to reduce symptoms of polydipsia by causing the body to absorb fluids more efficiently (reduction of diarrhea, induces constipation) and it causes the body to retain more sodium; thus a zinc deficiency can be a possible cause.
Polydipsia in psychiatric subsets
Psychogenic polydipsia is an excessive water intake seen in some patients with mental illnesses such as schizophreniaSchizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...
, and/or the developmentally disabled. It should be taken very seriously, as the amount of water ingested exceeds the amount that can be excreted by the kidneys, and can on rare occasions be life-threatening as the body's serum sodium level is diluted to an extent that seizures and cardiac arrest can occur.
While psychogenic polydipsia is generally not found outside the population of serious mental disorders, there is some anecdotal evidence of a milder form (typically called 'habit polydipsia' or 'habit drinking') that can be found in the absence of psychosis or other mental conditions. The excessive levels of fluid intake may result in a false diagnosis of 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 diagnostic results that closely mimic those of mild diabetes insipidus. As discussed in the entry on 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...
, "Habit drinking (in its severest form termed psychogenic polydipsia) is the most common imitator of diabetes insipidus at all ages. While many adult cases in the medical literature are associated with mental disorders, most patients with habit polydipsia have no other detectable disease. The distinction is made during the water deprivation test, as some degree of urinary concentration above isosmolar is usually obtained before the patient becomes dehydrated." However, prior to a water deprivation test, consideration should be given to a psychiatric consult to see whether it is possible to rule out psychogenic polydipsia or habit polydipsia.
Diagnosis
Polydipsia is a symptom (evidence of a disease state), not a disease in itself. As it is often accompanied by polyuriaPolyuria
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...
, investigations directed at diagnosing 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...
and diabetes mellitus
Diabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
can be useful. Blood serum tests can also provide useful information about the osmolality of the body's extracellular fluids. A decrease in osmolality caused by excess water intake will decrease the serum concentration of red blood cells
Hematocrit
The hematocrit or packed cell volume or erythrocyte volume fraction is the percentage of the concentration of red blood cells in blood. It is normally about 45% for men and 40% for women...
, blood urea nitrogen
Blood urea nitrogen
The blood urea nitrogen test is a measure of the amount of nitrogen in the blood in the form of urea, and a measurement of renal function. Urea is a by- product from metabolism of proteins by the liver and is removed from the blood by the kidneys.-Physiology:The liver produces urea in the urea...
(BUN), and sodium.