Sodium and potassium excretion in patients with ileostomies

The output of sodium and potassium from urine and ileostomy was investigated in 35 healthy patients with ileostomies; 17 had undergone proctocolectomy for ulcerative colitis and 18 for Crohn's colitis. Fifteen of the patients with Crohn's disease had also had small bowel resections, varying from 15 to 46% of the original bowel length. The patients were investigated at home because most studies of sodium and water balance in patients with ileostomies have been done in hospital wards, which may not reflect actual conditions. Mean (SD) ileostomy output was 565 (152) ml in patients with ulcerative colitis and 1,267 (540) ml in patients with Crohn's disease. The intrapatient variation was limited, whereas the interpatient variation was significant and correlated with the length of small bowel resected. The sodium concentration in the ileostomy discharge was 110 (9.2) mmol/l and did not change consistently with ileostomy volume. The potassium concentration was 10 (2.1) mmol/l. There was a significant inverse correlation between daily ileostomy sodium output and urinary sodium concentration (r = -0.44, p less than 0.01), and a significant correlation between the daily output of sodium in ileostomy contents and the sodium:potassium ratio in urine. We conclude that patients with ileostomies are at risk of sodium and water depletion, particularly those who have had small bowel resections. Increased sodium output from the ileostomy is associated with a reduction in the sodium:potassium ratio in the urine. To screen patients at risk, an estimate of the sodium balance can be made by measuring sodium and potassium concentrations in a single specimen of urine.