VP04.13: Evaluating the IOTA ultrasound features and classification in women with endometriosis

To evaluate the IOTA classification in patients with endometriosis. Patients, with cysts, were prospectively included at the Gynecologic Department, Rigshospitalet, Denmark from Jan. 2020. Cysts were described using IOTA terminology. Clinical decisions were not based on IOTA classification. We performed a retrospective application of IOTA simple rules in cases w. endometriosis. CA-125 levels were evaluated when available. N= 47 patients (median age 41 years (range 24 – 72)) w. histologically verified endometriosis were included. 3 had co-existing pathology (2 dermoids and 1 borderline ovarian tumour). 34/47 (72.3%) were examined by an IOTA certified gynecologist. Cysts were classified as: 17 unilocular, 2 unilocular solid, 16 multilocular, 7 multilocular solid, and 5 solid. B features present in 35/47 (74.6%) (20 w. 2 B-features and 2 w. 3 B-features): 17 unilocular lesions (B1), 4 w. acoustic shadowing (B3), 10 smooth multilocular lesions w. diameter < 100mm (B4), and 28 w. colour score 1 (B5). M features were present in 4/47 cases (8.5%); 1 w. ascites (M2), 2 w. ≥4 papillary structures (M3), and 1 irregular multilocular solid lesion w. diameter ≥100mm (M4). In 8/47 (17.0%) cases both B and M features were present or not applicable. According to simple rules, 35 should be classified as benign, 4 as malignant & 8 not classifiable. CA125 was ≥ 35 U/ml in 29/38 (76.3%) measured cases (median 62 U/ml (range 7–1490)). Based on routine ultrasound (US) & CA-125, clinicians classified cysts as suspected endometriosis 35/47 (74.5%), benign cyst 5/47 (10.6%) and borderline/malignant 7/47 (14.9%). CA-125 (n = 8) and/or US (n = 7) led to PET-CT scan before surgery in 15/47 (32%) despite endometriosis suspicion. 3/47 (6.4%) were operated by laparotomy because PET-CT scan did not exclude malignancy suspicion. Simple rules classified endometriosis better than routine US and CA-125. Endometriosis is a challenging diagnosis in a tertiary centre, primarily using risk of malignancy index for triage. Positive PET-CT lead to unnecessary laparotomy in 3 cases.