OC06: Diagnostic accuracy and potential limitations of transvaginal sonography for bladder endometriosis

We sought to evaluate the accuracy and potential limitations of transvaginal sonography (TVS) in the preoperative evaluation of patients with bladder endometriosis. Over 656 patients operated between 2001 and 2006 at our institution for suspected pelvic endometriosis, 41 had bladder endometriosis diagnosed at surgery. Findings at preoperative TVS were compared to those at surgery and histopathology. Bladder endometriosis was correctly identified at TVS in 18/41 patients (43.9%) (Group A), but in 23/41 cases (56.1%) (Group B) TVS did not reveal the presence of the endometriotic nodule. The sensitivity and specificity, positive and negative predictive values of TVS for bladder endometriosis were respectively 43%, 100%, 100% and 96%; the accuracy was 96%. The overall mean size of bladder endometriotic lesion at histological examination was 34.88 ± 19.35 (range, 10–92) mm. In patients correctly classified (Group A) the mean lesion diameter was 42.50 ± 22.07 (range 10–92) mm while Group B the mean lesion diameter was significantly less (28.9 ± 14.83 mm; range, 10–60 mm) (P = 0.029). All nodules with mean diameter > 35 mm were correctly diagnosed and 11/14 (78.6%) patients who needed cystotomy and bladder segmental resection were correctly diagnosed. No significant differences between the two groups with regard to age and severity of preoperative dysuria were found; 12/18 (70.6%) of Group A patients had previous surgery for endometriosis and only 5/23 (29.4%) patients in Group B had a history of pelvic surgery for endometriosis (P = 0.005). This study based on a large patient population demonstrates that TVS is accurate in the preoperative diagnosis of bladder endometriosis. Moreover accuracy is strongly correlated with the mean size of the lesion and with the clinical suspicion of pelvic endometriosis that emerges from a careful consideration of medical/surgical history.