Abdominal wall endometriosis: differentiation from other masses using CT features

To assess the utility of morphologic and quantitative CT features in differentiating abdominal wall endometriosis (AWE) from other masses of the abdominal wall.

Retrospective IRB-approved study of 105 consecutive women from two institutions who underwent CT and biopsy/resection of abdominal wall masses. CTs were independently reviewed by two radiologists blinded to final histopathologic diagnoses. Associations between CT features and pathology were tested using Fisher's Exact Test. Sensitivity, specificity, positive, and negative predictive values were calculated. P values were adjusted for multiple variable testing.

24.8% (26/105) of patients had histologically proven abdominal wall endometriosis. The other most common diagnoses included adenocarcinoma NOS (21%; 22/105), desmoid (14.3%; 15/105), and leiomyosarcoma (8.6%; 9/105). CT features significantly associated with endometriosis for both readers were location below the umbilicus (P = 0.0188), homogeneous density (P = 0.0188), and presence of linear infiltration irradiating peripherally from a central soft tissue nodule (i.e., "gorgon" sign) (P < 0.0001). The highest combined sensitivity (0.69, 95% CI: 0.48-0.86) and specificity (0.97, 95% CI: 0.91-1.00) for both readers occurred for patients having all three of these features present. Border type (P = 0.0199) was only significant for R2, peritoneal extension (P = 0.0188) was only significantly for R1, and the remainder of features were insignificant (P = 0.06-60). There was overlap in Hounsfield units on non-contrast CT (N = 26) between AWE (median: 45HU, range: 39-54) and other abdominal wall masses (median: 38.5HU, range: 15-58).

CT features are helpful in differentiating AWE from other abdominal wall soft tissue masses. Such differentiation may assist decisions regarding possible biopsy and treatment planning.