Comparison of magnetic resonance imaging and ultrasonography in the early diagnosis of interstitial pregnancy

OBJECTIVE: To investigate the usefulness of ultrasonography (USG) and magnetic resonance imaging (MRI) in the early diagnosis of interstitial pregnancy. STUDY DESIGN: Four cases of interstitial pregnancy that showed characteristic ultrasonographic and MRI findings were studied. All cases received cornual resection, and the presence of interstitial pregnancy was confirmed by pathologic examination. RESULTS: Three of four cases had a gestational sac in the uterine cornu or a protruding cornual mass and myometrium between the sac and uterine cavity on both USG and MRI. In the remaining case, preoperative diagnosis was inconclusive because no gestational sac was demonstrated by USG or MRI. Color flow mapping was conducted in three cases and revealed prominent peritrophoblastic blood flow. CONCLUSION: The findings suggest that USG combined with color flow mapping is the first choice in the early diagnosis of interstitial pregnancy. MRI, which is an extremely expensive imaging technology, should be used only if transvaginal USG with color flow mapping is inconclusive in ruling out the diagnosis of interstitial pregnancy.