18–22 September 2011, Los Angeles, CA, USA Oral poster abstracts stored by this examiner. A second examiner, unaware of real-time ultrasound, evaluated the 3D volumes using multiplanar display and virtual navigation and also had to provide a presumptive diagnosis (benign or malignant). This second examiner, like the first one, had information about patient’s age, menopausal status and complaints. All women underwent surgery or were followed-up until cyst resolution. Both examiners were experts on gynecological ultrasound. Histologic diagnosis was used as gold standard. Cysts that resolved spontaneously were considered as benign for analytical purposes. The Kappa index was used to assess the agreement between real time ultrasound and 3D-volume analysis. Sensitivity and specificity of both methods were calculated and compared using McNemar test. Results: Forty-one masses were malignant and fifty-eight were benign. Agreement between real-time ultrasound and 3D volume analysis was very good (Kappa index: 0.82, 95%CI: 0.70–0.93). Sensitivity for real-time ultrasound and 3D-volume analysis were 100% and 93%, respectively (McNemar test, P = 1.000). Specificity for real-time ultrasound and 3D-volume analysis were 91% and 84%, respectively (McNemar test, P = 1.000). Conclusions: Off-line 3D volume analysis may be a useful method for assessing adnexal masses, showing a good agreement with real-time ultrasound and having a similar diagnostic performance. OP24.07 Morphological and vascular ultrasound characteristics of pelvic masses of non-gynecological origin M. Zikan 1 , D. Fischerova 1 , I. Pinkavova 1 , P. Dundr 2 , D. Cibula 1 1 Oncogynecologic Center, Clinic of Obstetrics and G, Charles University, First Faculty of Medicine, Prague, Czech Republic; 2 Department of Pathology, Charles University, 1 st Faculty of Medicine and General University Hospital, Prague, Czech Republic Objectives: Analysis of the ultrasound (sonomorphologic, vascular and physical) characteristics of non-gynecological pelvic tumors. Identification of ultrasound characteristics typical for most common non-gynecological tumors in the pelvis. Methods: In a group of patients with pelvis mass who had undergone ultrasound examination with subsequent surgery or tru-cut biopsy revealing non-gynecological origin of such tumor, we retrospectively analyzed set of sonomorphologic, physical and vascular parameters. All the parameters were evaluated for the whole group of non- gynecological tumors as well as separately for each specific tumor type. Results: A total of 92 patients were included in this study. The most frequent non-gynecological malignancies were: colorectal cancer, followed by upper gastrointestinal tract tumors (pancreas, gall bladder), lymphoma, Krukenberg tumor and breast cancer; other cancers were represented by small number of cases. In our study, features indicative of a non-gynecologic tumor in pelvis included particularly non-ovarian or retroperitoneal location of the tumor, solid structure or solid component (no tumor without at least the solid component) and presence of necrosis. Conclusions: The analysis of ultrasound characteristics allowed for determining the parameters typical for pelvic tumors of non- gynecological origin. Some of these parameters have not been previously described (i.e. necrosis). OP24.07: Table 1. Most frequent parameters or parameters probably typical for non-genital tumors Location Non-ovarian or retroperitoneal (50%); retroperitoneal (42.31%) Laterality Unilateral (87.04%) Structure Completely solid or solid component (100%) Echogenity Necrosis (in completely solid tumors 51.8%; in solid component 83.67%) Vascular features Grade 3 in subjective assessment (average) Metastases Liver metastases (33.96%) OP24.08 Intra- and inter-observer reproducibility of two morphological ultrasound features of adnexal masses and of ultrasound diagnosis regarding malignancy L. Zannoni 1,2 , L. Savelli 1 , L. Jokubkiene 2 , A. Di Legge 3 , G. Condous 4 , A. Testa 3 , P. Sladkevicius 2 , L. Valentin 2 1 Gynaecology and Reproductive Medicine Unit, S.Orsola-Malpighi University Hospital, Bologna, Italy; 2 Obstetrics & Gynaecology, Malm ¨ o University Hospital, Lund University, Malm ¨ o, Sweden; 3 Obstetrics & Gynaecology, Catholic University of the Sacred Heart, Roma, Italy; 4 Early Pregnancy and Advanced Endosurgery Unit, Nepean Clinical School, University of Sydney, Sydney, NSW, Australia Objectives: To determine intra- and inter-observer reproducibility of two morphological ultrasound features of adnexal masses and of ultrasound diagnosis regarding malignancy. Methods: Gray scale videoclips of 83 adnexal masses were evaluated independently twice by 4 experienced and 3 less experienced ultrasound examiners. The variables analyzed were tumor type (unilocular, unilocular solid, multilocular, multilocular solid, solid), presence of papillary projections and ultrasound diagnosis (benign, borderline, malignant). Intraobserver repeatability was evaluated for each observer. Interobserver agreement was calculated between the experienced observers (6 pairs), between the less-experienced observers (3 pairs) and between observers with different levels of experience (2 pairs with observers from the same and one pair with observers from different institutions). Results are presented as agreement (%) and Cohen’s kappa (k) (weighted k for diagnosis) and expressed as the mean (range) of the respective pairs. Results: Intraobserver agreement for tumor type was 90.5% (87–95), k .88 (.83–.94), for presence of papillary projections 95% (92–100), k .82 (.72–1) and for diagnosis 93% (85.5–98), k .88 (.78–.94). Interobserver agreement for the three variables was respectively 79% (72–84), k .73 (.65–.80), 86% (81–89), k .58 (.38–.66), 87% (83–91.5), k .82 (.76–.87) for the experienced examiners and 71% (67–75), k .66 (.58–.67), 87% (84–89), k .43 (.35–.58), 81% (78–83), k .71 (.66–.74) for the less experienced examiners. Interobserver agreement was higher for observers with different levels of experience coming from the same than from different institutions: 85% (84–86), k .80 (.79–.81), 89% (87–90), k .61 (.52–.70), 85.5% (84–87), k .78 (.75–.81) vs. 61% (k .51), 76% (k .15), 79.5% (k .67). Conclusions: Intraobserver agreement with regard to tumor type, presence of papillary projections and diagnosis was excellent irrespective of level of experience. Interobserver agreement was fair to good and was best for diagnosis. OP25: NORMAL AND ABNORMAL FETAL GROWTH OP25.01 Gestational age determination by last menstrual period versus crown–rump length in a United States cohort M. Rosner , J. Gebb, P. Dar OBGYN, Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, NY, USA Objectives: ACOG recommends re-dating by 1 st trimester ultrasound (US) if the discrepancy between gestational age by LMP (LMPGA) and ultrasound (USGA) is > 7 days at < 12 weeks or > 10 days at 12–20 weeks. We sought to evaluate the discrepancy and the need for re-dating in our patient population. Methods: Retrospective review of 5117 singleton gestations with an US performed at 6–14 weeks from January 2009–2011. Patients with unknown LMP, LMPGA/USGA discrepancy of >4 weeks, fetal anomaly or NT> =3 mm were excluded. LMPGA/USGA Ultrasound in Obstetrics & Gynecology 2011; 38 (Suppl. 1): 56–167 127