Risk of colorectal cancer following CT-verified acute diverticulitis: a nationwide population-based cohort study

Aim: Routine colonoscopy to exclude colorectal cancer (CRC) after CT-verified acute diverticulitis is controversial. This study aimed to compare the incidence of CRC in patients with acute diverticulitis with that in the general population.

Method: Patients with an emergency admission for diverticular disease to any Norwegian hospital between 1 January 2008 and 31 December 2010 were included through identification in the Norwegian Patient Registry using International Classification of Diseases (ICD-10) codes K57.1-9. To estimate the age-specific distribution of CT-verified acute uncomplicated diverticulitis (AUD) and acute complicated diverticulitis (ACD) in this nationwide study population, numbers from the largest Norwegian emergency hospital were used. Patients diagnosed with CRC within 1 year following their admission for acute diverticulitis were detected through cross-matching with the Cancer Registry of Norway. Based on both Norwegian age-specific incidence of CRC and estimated age-specific distribution of CT-verified diverticulitis, standard morbidity ratios (SMRs) were calculated.

Results: A total of 7473 patients with emergency admissions for diverticular disease were identified (estimated CT-verified AUD n = 3523, ACD n = 1206); of these 155 patients were diagnosed with CRC within 1 year. Eighty had a CT-verified diverticulitis at index admission [41 AUD (51.3%); 39 ACD (49.7%)]. Compared with the general population, the SMR was 6.6 following CT-verified AUD and 16.3 following ACD, respectively.

Conclusion: In the first year after CT-verified acute diverticulitis, especially after ACD, the risk of CRC is higher than in the general population. This probably represents misdiagnosis of CRC as acute diverticulitis. Follow-up colonoscopy should be recommended to all patients admitted with acute diverticulitis.