OC162: Presence of acoustic streaming in different types of adnexal masses

Acoustic streaming is the movement of fluid in a cyst due to energy transfer from the US wave. A previous study reported that absence of acoustic streaming could be a typical characteristic of an endometrioma (Eoma). The aim is to examine which type of adnexal masses demonstrate acoustic streaming. IOTA phase 2 included patients with an adnexal mass in 19 different centers. Patients were scanned following the same standardized US protocol. The primary outcome was the histological diagnosis. More than 40 demographic and US variables were mandatory, but the evaluation of acoustic streaming was optional. 1940 patients were included, acoustic streaming was evaluated in 1128 cases of which 868 (77%) were benign and 260 (23%) malignant. Acoustic streaming was absent in 1022 (91%) masses and present in 105 (9%) of which 82 (78%) were benign and 23 (22%) malignant. Masses that demonstrated acoustic streaming were 26 Eomas, 21 serous cystadenofibromas, 15 mucinous cystadenofibromas, 10 teratomas,, 3 functional cysts, 3 hydrosalpinges,, 2 simple cysts, 2 rare benign tumors, 12 invasive carcinomas, 10 borderline tumors and 1 metastatic tumor. Masses with acoustic streaming were larger (median for the maximum diameter of the lesion was 88 mm versus 66 mm) and more often had low level echogenicity of the cyst content (63/105 (60%) versus 184/1022 (18%)). The presence of acoustic streaming to discriminate between Eomas and other types of adnexal masses reached a sensitivity of 89.7% (228/254), a specificity of 9.03% (79/874), LR+ 0.986 and LR− 1.14. Eomas with acoustic streaming were larger (median of max diameter lesion 66 mm versus 54.5 mm) and more often had low level echogenicity (30% versus 7%). This study confirms our previous report that acoustic streaming can also be present in Eomas and therefore can not be used as an ultrasound variable to exclude Eomas. It is more often present in large adnexal masses with low level echogenicity.