Improved Identification of Occult Peritoneal Endometriosis Using ABCt

BACKGROUND: Peritoneal endometriosis is the most common form of endometriosis and often overlooked due to its variable and nonpigmented appearance. Despite advances, identifying occult lesions remains challenging. The Aqua Blue Contrast Technique (ABCt), using retroperitoneal methylene blue infusion, was developed to enhance lesion visibility. METHOD: A total of 126 specimens from 14 women undergoing laparoscopic surgery for peritoneal endometriosis were evaluated using a sequential inspection protocol: initial visual assessment by a gynecology resident, followed by an experienced surgeon, and finally after applying the ABCt. The primary outcome was the number of endometriosis lesions identified by each observer. Secondary outcomes included lesion distribution and positive predictive values. RESULTS: In excised specimens, 78 (61.9%) of them were histologically confirmed as endometriosis. Endometriosis lesions were distributed as follows: posterior pelvic sidewall, 35 (44.9%); anterior pelvic sidewall, 22 (28.2%); and cul-de-sac, 21 (26.9%). For total specimen counts, the surgeon identified 59/78 lesions from 76 specimens (75.6%), and the resident 43/78 from 52 specimens (55.1%). Compared with these groups, ABCt identified 24.4% more lesions than the surgeon and 44.9% more than the resident. Subgroup analysis confirmed that ABCt achieved significantly higher detection rates than the resident across all pelvic sites and outperformed the surgeon at the cul-de-sac and posterior pelvic sidewall. CONCLUSIONS: Retroperitoneal contrast staining with ABCt improves the intraoperative detection of occult and nonpigmented peritoneal endometriosis lesions, supporting more comprehensive excision and reducing the chance of missed lesions.