1582 A Case of Complicated Diverticulitis Masquerading as Crohn's Disease: A Diagnostic Dilemma

Abstract

INTRODUCTION: Diverticular disease can have a complicated course in patients younger than 40 years of age and may mimic Crohn's disease (CD), thus presenting a diagnostic challenge. We report a case of a young adult presenting with complicated diverticulitis which was initially mistaken as CD. CASE DESCRIPTION/METHODS: A 31 year old man was admitted for left flank pain for 6 months and a flank mass for a week associated with weight loss, fever and fatigue. Exam showed a tender palpable mass in the left flank. Initial laboratory data showed leukocytosis of 13.7 k/uL with elevated ESR and CRP. Inflammatory bowel disease (IBD) serology was consistent with CD. Abdominal CT showed mural thickening of the descending and sigmoid colon with multiple fistulae extending into the left flank muscles and a diagnosis of CD was suggested by radiology. Colonoscopy showed erythematous mucosa in the descending colon with normal terminal ileum and biopsy showing stromal fibrosis with lymphoid aggregates. CT guided incision and drainage (I&D) was performed and patient was treated with antibiotics. Within 4 weeks of his discharge he had a similar presentation requiring repeat I&D. The clinical presentation, patient's young age, positive serology and radiological findings led to a presumptive diagnosis of CD. Infliximab was started but he continued to have hospitalizations for recurrent retroperitoneal abscesses. Finally, a left hemicolectomy was done. Pathology showed acute and chronic diverticulitis with mural scarring and abscess formation without any evidence of granulomas, ulcerations and crypt abscesses to suggest IBD. DISCUSSION: Diverticular disease has been described as not only rare but virulent in young patients. 25% of patients with diverticulitis develop complications including perforation, fistulae, obstruction or a stricture which can mimic CD. Although a common site of involvement in diverticulitis, the sigmoid colon is also involved in 70% of cases in Crohn's colitis. Radiologic findings can mimic the features of CD in complicated diverticulitis. IBD serology can be misleading due to its low specificity. Histologically, granulomas are only seen in 30% of cases in CD. No response to CD therapy can sometimes be the only clue to review the diagnosis. Differential may also include segmental colitis associated with diverticulosis that can develop into CD. This case highlights the virulent course of diverticulitis in young patients and serves as a reminder to have a high index of suspicion in this population.