Preoperative use of angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers and diuretics increases the risk of dehydration after ileostomy formation: population-based cohort study.

Background: Readmission rates following ileostomy formation are high. Dehydration and consecutive renal failure are common causes of readmission, potentially pronounced by drugs affecting the homeostasis. The aim of the study was to assess the risk of dehydration after ileostomy formation in patients treated with angiotensin-converting enzyme inhibitors (ACEI), angiotensin II receptor blockers (ARB) or diuretics.

Method: This nationwide population-based cohort study used data derived from the Colorectal Cancer Data Base of several Swedish healthcare registers. The study included all patients operated on with elective anterior resection and temporary ileostomy for rectal cancer clinically staged I-III in Sweden in 2007-2016. Exposure was at least two dispensations of ACEI, ARB or diuretics within 1 year prior to surgery. Outcome was 90-day readmission due to dehydration including acute renal failure.

Results: In total, 3252 patients were included with 1173 (36.1%) exposed to ACEI, ARB or diuretics. The cumulative incidence for 90-day readmission due to dehydration was 29.0% (151 of 520) for exposed versus 13.8% (98 of 712) for unexposed. The proportion of readmissions due to any reason was 44.3% (520 of 1173) for exposed compared to 34.2% (712 of 2079) for unexposed. The incidence rate ratio for readmission due to dehydration was 2.83 (95% c.i. 2.21 to 3.63, P < 0.001). The hazard rate ratio was 2.45 (95% c.i. 1.83 to 3.27, P < 0.001) after adjusting for age, gender and comorbidity.

Conclusion: Medication with ACEI, ARB or diuretics defines a vulnerable patient group with increased risk of readmission due to dehydration after ileostomy formation.