Diagnosis of interstitial pregnancy with sonography

Interstitial pregnancy is a rare and extremely dangerous form of ectopic pregnancy. Preoperative diagnosis of this condition prior to rupture is difficult, and early detection is essential to avoid a fatal outcome. Six cases in our series were diagnosed as interstitial pregnancy. Their clinical features were missed period, positive pregnancy test, and sudden onset of lower abdominal pain with or without vaginal spotting. The sonographic images showed an endometrial echo in uterine cavity, eccentric sac, protruding mass over the cornual area, and/or the presence of free fluid in the cul-de-sac. Five of 6 patients had sacs found in the cornual area or a protruding cornual mass. We termed the sonographic findings of interstitial pregnancy as "pregnancy in cornus." High resolution transvaginal sonography permits determination of the exact location of the gestational sac and increases the diagnosis rate of interstitial pregnancy.