Differentiation between small (< 4.5 cm) true subepithelial tumors and ectopic pancreas in the small bowel on computed tomography enterography.

OBJECTIVES

To identify imaging features that can differentiate ectopic pancreas from true subepithelial tumors (SETs) in the small bowel using CT enterography and to assess whether radiologists' performance for the differentiation can be improved with the knowledge of significant CT findings.

METHODS

CT images of ectopic pancreas (n = 29) and pathologically proven SETs (n = 61) were retrospectively reviewed by two radiologists in consensus. CT items analyzed included lesion location, contour (round, ovoid, flat/conformed), growth pattern, margin, homogeneity, necrosis, feeding vessel, surface ulceration, and enhancement pattern. For quantitative analysis, Hounsfield unit, longer diameter (LD), and shorter diameter (SD) of the lesion were measured. Univariate and multivariate analyses were performed. Diagnostic performance for differentiating ectopic pancreas from SETs was independently evaluated by two other radiologists using a receiver operating characteristic analysis.

RESULTS

Age < 63 years, female sex, flat/conformed appearance, homogeneous enhancement, the absence of feeding vessels and necrosis, and an LD/SD ratio > 1.5 were significant variables for differentiating ectopic pancreas from small bowel SETs (p < 0.05). In the multivariate analysis, flat/conformed appearance, the absence of feeding vessels, and female sex remained suggestive features for ectopic pancreas. Area under the curve values for differentiating between two disease entities increased by both independent reviewers with knowledge of these significant CT features.

CONCLUSIONS

Ectopic pancreas in the small bowel can be effectively differentiated from small (< 4.5 cm) true SETs by a flat/conformed appearance and the absence of feeding vessels on CT enterography. In addition, radiologists' performance for differentiating ectopic pancreas from small bowel SETs was improved with the knowledge of these significant CT findings.

KEY POINTS: • Ectopic pancreas in the small bowel can be differentiated from small (< 4.5 cm) subepithelial tumors on CT. • Differential CT findings of the ectopic pancreas are a flat or conformed appearance and the absence of a feeding vessel. • Radiologists' performance for differentiating ectopic pancreas from small bowel SETs can be improved with the knowledge of differential CT findings.