Influence of Complex Disease on the Accuracy of Transvaginal Ultrasound Diagnosis of Uterosacral Ligament Endometriosis.

Objective: To assess the impact of complex disease states, including pouch of Douglas (POD) obliteration and deep endometriosis (DE) of the bowel, on the diagnostic accuracy of transvaginal ultrasound (TVUS) for detecting endometriosis of the uterosacral ligaments (USLs) and torus uterinus (TU). Methods: This diagnostic accuracy study evaluated the performance of TVUS in diagnosing DE of the USLs and TU, using laparoscopic visualisation with histological confirmation as the reference standard among two previously reported prospectively collected cohorts. Complex disease states were defined as complete POD obliteration and/or DE of the bowel. Diagnostic accuracy metrics, including sensitivity, specificity, positive and negative predictive values (PPV) and likelihood ratios (LR), were calculated before and after the exclusion of complex disease cases. Results: Among 177 participants, 18.6% (33/177) had POD obliteration, 18.6% (33/177) had DE of the bowel and 16.4% (29/177) had both. Accuracy ranged from 93.1% to 94.7% for USLs and 97.2%-98.5% for TU, with minimal change after exclusion (≤ 1.5%). Sensitivity declined following exclusion, by -6.4% (left USL), -3.5% (right USL) and -2.7% (TU) after POD obliteration exclusion and further decreases of -1.8%, -3.4% and -4.4%, respectively, after bowel DE exclusion. Specificity remained ≥ 97.8% across all sites and reached 100% at the USLs after POD obliteration exclusion. Conclusions: Contrary to the assumption that complex disease states hinder TVUS accuracy, their presence may enhance lesion recognition, likely due to increased sonographic attentiveness when severe disease is suspected. While TVUS remains highly specific, its sensitivity decreases in the absence of complex disease, emphasising the need for meticulous and systematic imaging approaches.