Abstract: Colonic diverticulitis is a common gastrointestinal disease which can be acute or chronic in course. In this paper we report the management of a patient with chronic colonic diverticulitis. The patient had an atypical clinical presentation, whose imaging showed a high likelihood of occupying lesions. PET/CT showed hypermetabolism focus and colonoscopy saw mucosal thickening, pathological return of inflammation in the acute phase, which were difficult in differential diagnosis with colorectal cancer and inflammatory bowel disease. After comprehensive consideration, follow-up observation was recommended and the diagnosis was finally clarified. The management of this patient demonstrates the importance of evidence-based medicine in the diagnosis and treatment of diseases.