Evaluating the CT diagnosis of Clostridium difficile colitis:: Should CT guide therapy?

OBJECTIVE. The purpose of this study was to further characterize the CT findings of Clostridium difficile colitis and to provide for the first time a diagnostic sensitivity, specificity, positive predictive value, and negative predictive value to help clinicians decide whether antibiotic treatment is warranted on the: basis of CT findings while awaiting stool test results (which may take as long as 48 hr). MATERIALS AND METHODS. A retrospective review covering a 4-year period was performed of the charts and CT scans of 54 symptomatic patients with stool test results positive for C. difficile and of a control group of 56 patients with antibiotic-associated diarrhea with stool test results negative for C. difficile. RESULTS. At our institution, C. difficile colitis was explicitly diagnosed at CT in these patients with a sensitivity of 52% specificity of 93%. positive predictive value of 88%, and negative predictive value of 67%. The sensitivity can be raised to 70% with no change in specificity with more rigid adherence to diagnostic criteria of colon wall thickening of greater than 4 mm combined with an; one or more findings of pericolonic stranding, colon wall nodularity, the "accordion" sign, or otherwise unexplained ascites. CONCLUSION. Although routine CT screening of antitbiotic-associated diarrhea is not advocated, the 88% positive predictive value of a diagnosis of C. difficile colitis in those who Lire scanned may merit consideration of treatment by clinicians on the basis of the CT results alone.