Incidence and recurrence rate of sigmoid diverticulitis in patients requiring admission to hospital in Iceland from 1985 to 2014: nationwide population‐based register study

Background Diverticulitis is the most common complication of diverticular disease, affecting 10–25 per cent of patients with diverticula. A retrospective, nationwide, population‐based cohort study was performed to analyse the incidence and recurrence rate of sigmoid diverticulitis requiring hospital admission. Methods All patients discharged from hospital in Iceland during 1985–2014 who were diagnosed with diverticular disease were included. The χ2 test was used to analyse the trend of the incidence in the period 2002–2014. The Kaplan–Meier method and the Cox model were used to analyse recurrence. Results Of 8660 admissions for diverticular disease, 4746 were due to diverticulitis, of which 2939 were for diverticulitis diagnosed for the first time. After the first attack, surgery was used to treat 661 patients. Of 2278 patients not treated by resection, 537 had a second attack (23·6 per cent). There was a significant decrease in the incidence of diverticulitis in patients aged 40–89 years during the period from 2002 to 2014 (P = 0·033). The risk of recurrence was associated with younger age at first attack and female sex (P