Tu1529 Endoscopic Colon Biopsies From Patients With Chronic Clostridium Difficile Infection Have No Characteristic Histologic Abnormalities

Tu1529 Endoscopic Colon Biopsies From Patients With Chronic Clostridium Difficile Infection Have No Characteristic Histologic Abnormalities Ahren C. Rittershaus, Suntrea Hammer, Barbara J. McKenna Pathology, University of Michigan Hospitals, Ann Arbor, MI Clostridium difficile infection is a common cause of hospitaland communityacquired diarrhea, often occurring after antibiotic treatment for a separate infection. Recommended therapy for acute C. difficile colitis is 10 days of metronidazole or vancomycin. The incidence and virulence of C. difficile is increasing, as is the rate of refractory infection, which we refer to as “chronic C. difficile infection” (CCDI). The histologic findings in acute C. difficile colitis are well documented and include focal surface epithelial necrosis with a neutrophilic infiltrate early in the disease, and complete mucosal necrosis with pseudomembrane formation in the late phase (Fig. 1b). We sought to characterize the histologic findings of CCDI, a previously unstudied area.CCDI was defined as two positive stool toxin assays between 10 days and 6 months apart. In our hospital between 2000 and 2008, 792 patients met these criteria. A review of the pathology database identified 137 patients of this group who had endoscopic colon biopsies within six months after their second positive assay. Clinical history was reviewed and seventy-one patients with a known cause of colitis were eliminated from the study, including ulcerative colitis (26), Crohn disease (5), lymphocytic colitis (1) and graft-versus-host disease (39). Sixty-six patients met criteria. Biopsies were reviewed and grouped into four categories: 1) Normal (Fig. 1a), 2) Severe acute C. difficile-like changes (Fig. 1b), 3) Mild changes (focal acute cryptitis, Fig. 1c, and focal chronic changes, Fig. 1d), and 4) Other. The indication for endoscopy in 61 of 66 cases was colitis, diarrhea or hematochezia. The remaining indications were abdominal pain, iron deficiency anemia, polyps (2) and diverticulosis. Endoscopic and histologic findings are summarized in Table 1. The two cases categorized as “other” include one case of diffuse active chronic colitis without features of acute C. difficile colitis and one case of diffuse healed mucosal injury. All 7 cases with severe acute C. difficilelike changes on histology had endoscopic findings of pseudomembranous or ischemic-type colitis. This is the first study to examine the histologic changes of CCDI. We found no characteristic histologic finding or set of findings associated with CCDI. Eighty-six percent of biopsies were either normal or had only mild, non-specific changes which would likely not alert either the pathologist or gastroenterologist to the possibility of C. difficile infection. These results are somewhat unanticipated as we expected CCDI to have either changes of acute C. difficile colitis or more severe combined active and chronic changes due to ongoing mucosal injury. In summary, gastroenterologists should not be surprised when a diagnosis of “normal” is rendered by a pathologist in a patient with CCDI.