Original article Assessment of recurrence and complications following uncomplicated diverticulitis N. C. Buchs 1 , B. Konrad-Mugnier 1 , A.-S. Jannot 2 , P.-A. Poletti 3 , P. Ambrosetti 1 and P. Gervaz 1 Departments of 1 Surgery, 2 Clinical Epidemiology and 3 Radiology, Geneva University Hospital and Medical School, Geneva, Switzerland Correspondence to: Dr P. Gervaz, Coloproctology Unit, Clinique La Colline, Avenue de la Roseraie 76A, 1205 Geneva, Switzerland (e-mail: pascalgervaz@gmail.com) Background: The natural history of sigmoid diverticulitis has been inferred from population-based or retrospective studies. This study assessed the risk of a recurrent attack following the first episode of uncomplicated diverticulitis. Methods: Patients admitted between January 2007 and December 2011 with a first episode of uncomplicated sigmoid diverticulitis confirmed on computed tomography were enrolled in this prospective study. After successful medical management of the first episode, follow-up was conducted through yearly telephone interviews. Cox proportional hazards regression was performed to model the impact of various parameters on eventual recurrences and complications. Results: During a median follow-up of 24 (range 3–63) months, 46 (16·4 per cent) of 280 patients experienced a second episode of diverticulitis. Six patients (2·1 per cent) subsequently developed complicated diverticulitis and four (1·4 per cent) underwent emergency surgery for peritonitis. In multivariable analysis, a raised serum level of C-reactive protein (over 240 mg/l) during the first attack was associated with early recurrence (hazard ratio 1·75, 95 per cent confidence interval 1·04 to 2·94; P = 0·035). Conclusion: Uncomplicated sigmoid diverticulitis follows a benign course with few recurrences and little need for emergency surgery. Registration number: NCT01015378 (http://www.clinicaltrials.gov). Paper accepted 6 February 2013 Published online in Wiley Online Library (www.bjs.co.uk). DOI: 10.1002/bjs.9119 Introduction Although sigmoid diverticulitis is common, there are no modern prospective data to elucidate the natural history. Original literature suggested a high risk of recurrence and subsequent complications 1 . However, recent series suggest that the natural history of sigmoid diverticulitis is more benign in the era of modern antibiotics 2 . Few series have looked at the true recurrence risk; the diagnosis was often based on clinical parameters without imaging by computed tomography (CT) 3,4 . This study was designed to assess the natural history of uncomplicated sigmoid diverticulitis diagnosed by CT. Methods Between January 2007 and December 2011, all patients with a first episode of uncomplicated diverticulitis, documented by CT and requiring admission to hospital, were included prospectively in the present study. Informed consent was obtained from all patients. The study was undertaken in accordance with ethical guidelines after being reviewed by the Ethics Committee for Clinical Research at this institution. This study was registered in ClinicalTrials.gov (registration number NCT01015378). Inclusion was based on a definition of simple diver- ticulitis that comprised clinical, biological, radiological and endoscopic criteria 5 : acute lower abdominal pain or discomfort; inflammatory syndrome (serum C-reactive protein (CRP) concentration over 50 mg/l or white blood cell count exceeding 11 × 10 9 /l); signs of inflammation of the sigmoid and/or descending colon on CT; and endo- scopic documentation of the presence of diverticula, while ruling out another associated condition. Exclusion criteria were: age younger than 18 or older than 85 years, malig- nancy, pericolic or pelvic abscess indicating complicated diverticulitis, an associated colorectal condition, and refusal to give informed consent.  2013 British Journal of Surgery Society Ltd British Journal of Surgery 2013; 100: 976–979 Published by John Wiley & Sons Ltd