OC139: Rudimentary horn pregnancy: early sonographic diagnosis confirmed by Magnetic Resonance Imaging

Abstract

To report two cases of rudimentary horn pregnancies (RHP) diagnosed at first trimester by sonography and confirmed by MRI, and to suggest criteria for prerupture sonographic diagnosis of this rare condition. We report on a case in which a routine sonographic examination of the 12th week pregnant nullipara demonstrated a gestational sac with a live fetus in a right uterine horn. A connection between the right horn with the uterine body and cervix could not be demonstrated. With MRI, the uterine body appeared normal, and a gestational sac in a non-communicating rudimentary horn was clearly demonstrated. In the second case, sonographic examination was performed due to vaginal bleeding at 11 weeks pregnancy. Again, a right unicornuate uterus was seen, and a non-communicating left rudimentary horn with a gestational sac including a small embryonic pole. MRI demonstrated a right empty uterus, and a pregnant horn without an endometrial communication to the uterine body. Both patients were operated by laparotomy and the pregnant rudimentary horns were resected with no complications. Histopathologic examination revealed abnormal placentation (accreta) in both pregnancies. We suggest the following criteria for sonographic diagnosis of preruptured RHP, in order to differentiate this condition from tubal pregnancy or pregnancies in a bicornuate or didelphic uterus: 1. a gestational sac within the uterine horn, surrounded by muscular tissue. 2. lack of direct and confluent continuity between the muscular tissue around the sac and the uterine body and cervix. 3. increased trophoblastic vascularization, assessed by color Doppler compared to normal trophoblast. Additionally, MRI can be used to confirm the diagnosis before an invasive procedure is taken.