OP09.02: Sonographic characteristics of abdominal wall endometriosis

To describe the sonographic characteristics of endometriotic lesions in the abdominal wall and assess the prevalence of coexisting intra-abdominal endometriosis. Consecutive women (n = 42, with 47 lesions) undergoing a structured transvaginal and transabdominal ultrasound examination, by an experienced examiner at Södersjukhuset, Stockholm during 2021–2022 with a histologically confirmed abdominal wall endometriosis (AWE) were included. The median age of the patients was 37 years (IQR 32-41), and the median BMI 25 (IQR 21-29). Ninety percent (38/42) had a history of previous surgery, most commonly Caesarean section (CS) (36/42, 86%). The majority (38/47, 81%) of lesions were located in or near a SC scar. In women without prior surgery, lesions were located in the Inguinal canal (n = 2), or in the umbilical region (n = 2). On ultrasound (US) three patients were diagnosed with endometriomas, and two with deep infiltrating endometriosis. According to US, the median maximal diameter was 21 mm (IQR 14-31). On US 44 lesions (94%) had an irregular shape, 45 (96%) had mixed echogenicity (25 with and 20 without hypoechoic cysts), and two were hypoechoic, vascularisation was absent in 25 (53%), and sparse in 22 (47%). Lesion location on US; skin, subcutaneous fat and muscle (n = 1), subcutaneous fat (n = 17), subcutaneous fat and fascia (n = 20), in the muscle under the fascia (n = 7), Inguinal canal (n = 2). In 27/40 (68%) the location of the lesion was confirmed at surgery. 7 lesions engaging the muscle fascia were misdiagnosed as subcutaneous, and 6 lesions subcutaneous lesions was suspected to engage the fascia. The most common localisation AWE is in or near a CS scar, in the subcutaneous tissue. On US, the majority of lesions have irregular shape, with mixed echogenicity with or without hypoechoic cysts, and with sparse or no vascularisation. Concurrent intraabdominal endometriotic manifestations are uncommon.