Diagnostic accuracy and potential limitations of transvaginal sonography for bladder endometriosis

Abstract

To evaluate the accuracy and the potential limitations of transvaginal sonography (TVS) in the preoperative evaluation of women with clinically suspected bladder endometriosis and to describe the sonographic features of the pathological condition in cases in which it was confirmed. In the period between 2001 and 2006, we operated on 490 patients with clinically/sonographically suspected endometriosis. In 41 cases, bladder endometriosis was diagnosed at surgery and confirmed at histopathological examination. All patients underwent TVS in a standardized manner not more than 1 month before surgery. Findings at preoperative TVS were described and compared with those at laparoscopy in order to evaluate the sensitivity, specificity, and positive and negative predictive values of TVS. Bladder endometriosis was correctly identified at TVS in 18/41 cases (43.9%) while 23/41 (56.1%) patients had a negative preoperative sonogram. The sensitivity, specificity and positive and negative predictive values of TVS for bladder endometriosis were 44% (18/41), 100% (449/449), 100% (18/18) and 95% (449/472), respectively, and the total accuracy was 95% (467/490). The detection rate was strongly related to mean lesion diameter as measured by the pathologist (mean +/- SD, 42.5 +/- 22.1 mm in the nodules detected vs. 28.9 +/- 14.8 mm in the nodules missed; P = 0.029) and to a history of previous surgery for endometriosis (70.6% vs. 25.0%; P = 0.005). At TVS, the nodule was hypoechogenic, its morphology was either elongated ('comma-shaped': 12/18, 66.7%) or spherical (6/18, 33.3%), and the site involved was the dome (11/18, 61.1%) or the base (7/18, 38.9%) of the bladder. Small anechogenic cystic areas within the nodule were seen in five of the 18 patients (27.8%) and a bright hyperechogenic rim was seen in 10 (55.6%). The detection rate of bladder endometriosis by TVS depends on the size of the endometriotic nodules, with detected nodules being larger than those that were missed. A history of previous surgery for endometriosis increases the likelihood of bladder endometriosis being detected on ultrasound examination.