Risk of Emergency Surgery or Death After Initial Nonoperative Management of Complicated Diverticulitis in Scotland and Switzerland

National guidelines on interval resection for prevention of recurrence after complicated diverticulitis are inconsistent. Although US and German guidelines favor interval colonic resection to prevent a perceived high risk of recurrence, UK guidelines do not. To investigate patient management and outcomes after an index inpatient episode of nonoperatively managed complicated diverticulitis in Switzerland and Scotland and determine whether interval resection was associated with the rate of disease-specific emergency surgery or death in either country. This secondary analysis of anonymized complete national inpatient data sets included all patients with an inpatient episode of successfully nonoperatively managed complicated diverticulitis in Switzerland and Scotland from January 1, 2005, to December 31, 2015. The 2 countries have contrasting health care systems: Switzerland is insurance funded, while Scotland is state funded. Statistical analysis was conducted from February 1, 2018, to October 17, 2019. The primary end point defined a priori before the analysis was adverse outcome, defined as any disease-specific emergency surgical intervention or inpatient death after the initial successful nonsurgical inpatient management of an episode of complicated diverticulitis, including complications from interval elective surgery. The study cohort comprised 13 861 inpatients in Switzerland (6967 women) and 5129 inpatients in Scotland (2804 women) with an index episode of complicated acute diverticulitis managed nonoperatively. The primary end point was observed in 698 Swiss patients (5.0%) and 255 Scottish patients (5.0%) (odds ratio, 0.98; 95% CI, 0.81-1.19). Elective interval colonic resection was undertaken in 3280 Swiss patients (23.7%; median follow-up, 53 months [interquartile range, 24-90 months]) and 231 Scottish patients (4.5%; median follow-up, 57 months [interquartile range, 27-91 months]). Death after urgent readmission for recurrent diverticulitis occurred in 104 patients (0.8%) in Switzerland and 65 patients (1.3%) in Scotland. None of the investigated confounders had a significant association with the outcome apart from comorbidity. This study found no difference in the rate of adverse outcome (emergency surgery and/or inpatient death) despite a 5-fold difference in interval resection rates.