Fluid Management in Diabetes Insipidus

Introduction to Fluid Management

Patients with diabetes insipidus (DI) can become "net secretors" where they lose more water and sodium than they consume orally, particularly those with short bowel remnants or high-output jejunostomies 1
The American Gastroenterological Association recommends that hypotonic fluids like water, tea, coffee, and alcohol should be limited, as they can worsen fluid losses rather than correct them 2

The European Society for Clinical Nutrition and Metabolism suggests that glucose in the gut lumen stimulates sodium absorption across the small intestine, which is followed by anions and water—this is the physiologic basis for why ORS works better than plain water 2
The World Health Organization recommends that oral rehydration solutions differ critically from commercial sports drinks: ORS has considerably higher sodium content and lower sugar content 2

The National Institute for Health and Care Excellence recommends that all patients with DI should have ad libitum (unrestricted) access to fluid to prevent dehydration, hypernatremia, growth failure, and constipation 1
For patients who can self-regulate their fluid intake, their own thirst sensation should guide consumption, as their osmosensors tend to be more sensitive and accurate than medical calculations 1
Patients may be allowed to drink up to 1000 mL daily of fluids of their choice regardless of osmolarity; additional fluid requirements should be met with isotonic glucose-saline solution 3

The modified World Health Organization cholera solution (St Mark's solution) is specifically recommended, with the following composition:

The American College of Physicians recommends that serum sodium, serum osmolality, and urine osmolality should be measured as initial biochemical work-up 1
Random urinary sodium <20 mmol/L suggests sodium depletion and inadequate treatment 3
A random urinary sodium >20 mmol/L should be the target of treatment 3
Urine output, changes in weight, and complaints of thirst should be monitored to assess adequacy of fluid replacement 2

For infants and young children who cannot self-regulate intake, water should be offered frequently on top of regular fluid intake, with normal-for-age milk intake maintained to guarantee adequate caloric intake 1
Tube feeding (nasogastric or gastrostomy) should be considered if patients have repeated episodes of vomiting and dehydration and/or growth failure 1