Granulomatous inflammation in sigmoid diverticulitis: two diseases or one?

Aims: Histological appearances indistinguishable from Crohn's disease have been described in patients undergoing sigmoid colectomy for complicated diverticular disease. To investigate whether this finding represents coincidental dual pathology or merely a granulomatous colitis confined to the diverticular segment, we undertook clinical follow-up of affected patients. Methods and results: Eight patients (median age 64 years, four males) whose sigmoid colectomy specimens showed acute diverticulitis and granulomatous inflammation were identified. All had a pre-operative diagnosis of diverticular disease and no previous evidence of Crohn's disease. Non-caseating epithelioid granulomas, unrelated to foreign material and usually unrelated to inflamed diverticula were present in the bowel wall of seven cases and in the regional lymph nodes of five. Three had granulomatous vasculitis and two had granulomas in 'background' mucosa. Mural lymphoid aggregates were identified in all cases. However, fissuring ulcers distinct from inflamed diverticula were not identified. On median follow-up of 51 months (range 18-112 months) none of the patients developed evidence of chronic inflammatory bowel disease. Three had died from unrelated causes. Conclusions: Granulomatous inflammation appears to be part of a spectrum of sigmoid diverticulitis, In this setting, caution should be exercised to avoid an inappropriate diagnosis of Crohn's disease.