Sigmoid cancer versus chronic diverticular disease: differentiating features at CT colonography.

Abstract

To retrospectively identify morphologic findings at computed tomographic (CT) colonography that are the most reliable in the differentiation of masslike chronic diverticular disease from sigmoid carcinoma in a large patient cohort. This study was approved by the institutional review boards. The need for signed consent was waived for this retrospective study. The cohort consisted of 212 patients (mean age, 68 years; 113 women, 99 men) with focal masslike findings in the sigmoid colon at CT colonography, representing chronic diverticular disease (n = 97) or sigmoid carcinoma (n = 115). CT colonography studies were scored according to presence or absence of potential discriminators by a panel of four readers in consensus. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated, and multivariate analysis was performed. Absence of diverticula in the affected segment showed high NPV and PPV (0.95 and 0.93, respectively). Also, shoulder phenomenon showed a high NPV (0.92) and PPV (0.75). Segment length of 10 cm or less (NPV, 0.85; PPV, 0.61) and destroyed mucosal folds (NPV, 1.00; PPV, 0.62) had a high NPV but a low PPV. Although segments affected by carcinoma often showed straightened and eccentric growth patterns, no thick fascia sign, and more and larger local-regional lymph nodes (all P < .05), NPV was insufficient for discrimination (NPV ≤ 0.66). Combination of absence of diverticula and presence of shouldering showed a high diagnostic certainty (93%). Carcinoma is best differentiated from masslike diverticular disease by the absence of diverticula in the affected segment and the presence of shoulder phenomenon.