A Case-Control Study of Sonographic Maximum Ovarian Diameter as a Predictor of Ovarian Torsion in Emergency Department Females With Pelvic Pain.

Abstract

Color and power Doppler ultrasound are commonly used in the evaluation of ovarian torsion but are unreliable. Because normal-sized ovaries are unlikely to cause torsion, maximum ovarian diameter (MOD) could theoretically be used as a screening test in the ED. Identification of MOD values below which torsion is unlikely would be of benefit to providers interpreting radiology department or point-of-care pelvic ultrasound. The objective was to determine if sonographic MOD can be used as a screening tool to rule out torsion in selected patients. Via a retrospective case-control study spanning a 14-year period, we examined the ultrasound characteristics of patients with torsion and age-matched controls, all presenting to the emergency department with lower abdominal pain and receiving a radiology department pelvic ultrasound for "rule-out torsion." Standardized data collection forms were utilized. Distributions of MOD were compared and sensitivity, specificity, and likelihood ratios were calculated for multiple cutoffs. We identified 92 cases of surgically confirmed ovarian torsion and selected 92 age-matched controls. In postmenarchal patients the sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of 3- and 5-cm MODs were 100% (96%-100%), 30% (20%-41%), 1.4 (1.3-1.7), and 0 and 91% (83%-97%), 92% (83%-97%), 11.2 (5.5-22.9), and 0.09 (0.04-0.19), respectively. The 5-cm MOD, however, excluded an additional 52 of 84 (62%) postmenarchal patients. A threshold MOD of 5cm on pelvic ultrasound may be useful to rule out ovarian torsion in postmenarchal females presenting with lower abdominal and pelvic pain.