An iso-osmolar oral supplement increases natriuresis and does not increase stomal output in patients with an ileostomy: A randomised, double-blinded, active comparator, crossover intervention study.

Background: Patients with an ileostomy often experience fluid and electrolyte depletion because of gastrointestinal loss. This study aimed to compare how an iso-osmolar and a hyperosmolar oral supplement affect ileostomy output, urine production, and natriuresis as proxy measurements of water-electrolyte balance.

Methods: In a randomised, double-blinded, active comparator, crossover intervention study, we included eight adult ileostomy patients who were independent of parenteral support. We investigated how an iso-osmolar (279 mOsm/kg) and a hyperosmolar (681 mOsm/kg) oral supplement affected ileostomy output mass, urine volume, and natriuresis. In addition to their habitual diet, each participant ingested 800 mL/day of either the iso-osmolar or hyperosmolar supplement in each of two study periods. Each period started with 24-hour baseline measurements, and the supplements were ingested during the following 48 h. All measurements were repeated in the last 24 h.

Results: No statistically significant changes in ileostomy output were detected following the intake of either oral supplement (median (range) 67 (-728 to 290) g/day, p = 0.25) despite increased fluid intake. Compared with the hyperosmolar supplement, the iso-osmolar supplement induced a statistically significant increase in urine volume (470 (0-780) mL/day, p = 0.02) and natriuresis (36 (0-66) mmol/day, p = 0.02).

Conclusion: Intake of the two oral supplements did not affect ileostomy output during this short intervention. Natriuresis increased following intake of the iso-osmolar supplement compared to that after ingesting the hyperosmolar supplement, indicating that patients with an ileostomy may benefit from increasing their ingestion of iso-osmolar fluids. ClinicalTrials.gov identifier:NCT03348709.