S1898 Clostridioides difficile Colitis Masquerading as Colorectal Malignancy

Abstract

Introduction: Clostridioides difficile (C. diff) is an enteric pathogen typically associated with the use of antimicrobials that disrupt the normal gut microbiome. Its endoscopic appearance ranges from patchy erythema, edema to large segmental pseudomembranes to sharply demarcated ulcers. We present a case of C. diff colitis masquerading as a friable mass concerning for malignancy. Case description/methods: This is a 60-year-old female with history of Lynch Syndrome without recent colonoscopy who presented with 3 weeks of right lower quadrant abdominal pain with profuse diarrhea, early satiety and unintentional weight loss. She had been hospitalized 2 weeks prior for septic shock with initial CT demonstrating pneumatosis intestinalis within the ascending colon. She was treated non-operatively and left against medical advice after subjective improvement in her symptoms. On repeat imaging, there was evidence of long segment terminal ileal wall thickening with resolution of her pneumatosis intestinalis. She was found to be C. diff positive and started on oral vancomycin therapy. A diagnostic ileocolonoscopy demonstrated circumferential sloughing and erythematous friable mucosa with narrowing in the terminal ileum and a large, lateral spreading, ulcerative mass in the sigmoid colon with associated stricture. Biopsies showed colonic mucosa with ulcer and crypt architectural distortion without dysplasia and malignancy. A repeat colonoscopy done 1 month after treatment given her history of Lynch Syndrome demonstrated complete resolution of her previous endoscopic findings. Discussion: While the endoscopic appearance of C diff colitis is well-described and variable, this is the first case, to our knowledge, of it mimicking as focal malignancy. C. diff may be endoscopically indistinct from acute infectious colitis or present as pseudomembrane colitis, a non-specific term used to describe acute endothelial damage characterized by multiple discrete, raised yellow plaques distributed over erythematous mucosa. It shares a pathogenic mechanism with ischemic colitis where blood flow and tissue oxygenation is disrupted with overlapping endoscopic features wherein the punctate pseudomembranes coalesce and form large segmental membranes. If focal, the edema and ulceration can resemble colonic adenocarcinoma with luminal narrowing by a lobulated mass effect. This clinical case highlights the importance of confirmatory histology and endoscopic re-evaluation.Figure 1.: Panel A: Initial CT demonstrated pneumatosis intestinalis in the ascending colon. Panel B: Repeat CT 2 showed terminal ileal wall thickening. Panel C: Ulcerative mass in the sigmoid colon with luminal narrowing Panel D: Circumferential sloughing and friable mucosa in the terminal ileum Panel E: Repeat colonoscopy with complete resolution of mucosal changes between previously tattooed sites Panel F: Repeat colonoscopy with healthy appearing terminal ileum mucosa.