Case history

Case history #1

A 46-year-old black man with chronic paranoid schizophrenia is admitted to the acute psychiatric unit for crisis stabilisation. During the course of his admission to hospital he is noted to continually ask staff for water and ice, stating: "I need to flush out the demons". Subsequently, he is found in his room drinking water out of the bath tap.

Case history #2

A 20-year-old female college student presents with increased polydipsia and polyuria since childhood. She has a fluid intake of 6 to 8 litres and a frequency of micturition of 20 to 25 times in a 24-hour period. She denies any psychiatric history and there is no evidence of dehydration, neurological abnormalities, or head trauma.

Other presentations

PPD is most commonly seen in people with schizophrenia, but may present in those with other psychiatric disorders and neurodevelopmental disorders.[1][2][3][4][5][6][7] Polydipsia may be diagnosed by an incidental finding of low plasma sodium (hyponatraemia) or by overt symptoms of water intoxication necessitating medical intervention.[8][9]

Polydipsia can occur in the absence of underlying medical or psychiatric conditions.[10] Increasing popularity of lifestyle programmes that advocate water drinking to improve overall health have led to a rise in polydipsia among the general population.[10]

Chronic excessive hydration may not manifest neurologically, due to volume adaptation by the brain.[11] Between 3% and 6% of patients with PPD and schizophrenia have hyponatraemia.[10][12] With mildly reduced serum sodium levels, symptoms may range from nausea and malaise to lethargy, headache, obtundation, seizures, and coma. Large and rapid fluid intake can lead to severe and symptomatic hyponatraemia. At very low serum sodium levels (<115 mmol/L [<115 mEq/L]), neurological symptoms manifest, due to intracerebral osmotic fluid shifts and cerebral oedema. In the most severe cases, progression to tentorial herniation, brain stem compression, and respiratory arrest can result in death.

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