Complications of colonic diverticulosis include diverticulitis, hemorrhage, perforation and stricture, and surgery should be immediately considered in case of poor response to conservative treatment. In this article, the authors report a recent case of colonic diverticulitis with various complications, from coloduodenal fistula to extensive stricture, along with a discussion of relevant literature. The subject was a 37-year-old male. Despite receiving treatment for recurrent colonic diverticulitis for five years, no cure had been achieved. Upper gastrointestinal series and other tests showed extensive stricture including ileocolonic fistula, coloduodenal fistula, colopancreatic tail fistula and mesenteric abscess. The patient did not respond to conservative treatment, and underwent a subtotal colectomy, end-to-end anastomosis of the ileum to sigmoid colon, and gastrostomy. No histopathologically recognized atypical cells were found, and inflammatory cell invasion and granulation tissue were seen in the diverticulum, hence a diagnosis of multiple colonic diverticulitis associated with repeated acute and chronic inflammation was made.