December 1, 2016

expert reaction to case study of a woman who drank too much water

BMJ Case Reports has reported a case of a woman who developed hyponatraemia (abnormally low sodium levels) after drinking an excessive amount of water in an attempt to help a recurrent urinary tract infection.

Prof Tom Sanders, Professor emeritus of Nutrition and Dietetics at King’s College London, said:

“This is a case report of a lady with cystitis drinking too much water, too quickly and developing hyponatraemia.  This condition only occurs when large volumes of water are consumed over a short period. Hyponatraemia is unlikely to occur with an intake less than 750 ml per hour (5 small plastic cups of water). NHS advice for people with cystitis is to drink plenty of water rather than drinking specialised alkalising fluids or cranberry juice.

“Although there is a lack of evidence from randomised controlled trials showing benefit this does not mean the advice is wrong. It is unlikely that such a trial could be done because there would be serious ethical concerns about conducting a trial which involved withholding water from patients.  This is because dehydration is a common and life-threatening problem in frail hospital patients.

“Water requirements are about 1ml/kcal energy which gives average fluid intakes of 2000 ml for women and 2500 ml for men. Some water comes with food (400-600 ml) but the rest needs to be drunk.

“It would be quite wrong to interpret this report as suggesting that doctor’s advice to drink plenty of water when you are ill is wrong. Patients should be provided with an adequate supply of water by their beds which they should be encouraged to drink or helped to drink.”

Prof Graham McGeown, Dunville Professor of Physiology at Queen’s University Belfast, said:

“People with an infection are usually advised to keep drinking to avoid dehydration, which is a risk if people stop drinking because they feel unwell, especially if they have a fever and are sweating. Clearly, as this case indicates, it is possible to go too far. It seems that the woman concerned took the doctor’s advice too seriously, drinking several litres in a short time and so dangerously diluting her body fluids.

“The ‘cure’, however, was to limit drinking to 1l (nearly 2 pints) in 24 hours – and not to stop drinking completely. Perhaps the lesson is that doctors need to be more specific in their guidance rather than avoiding advice on drinking in these circumstances.”

* ‘When plenty is too much: water intoxication in a patient with a simple urinary tract infection’ by Laura Christine Lee and Maryann Noronha was published in BMJ Case Studies on Thursday 1st December.

Declared interests

None declared