Interstitial ectopic pregnancy (sometimes called cornual) occurs in the interstitial portion of the fallopian tube. It accounts for 2-4% of all ectopics. The morbidity and mortality are higher due to later presentation, and the tendency to massive hemorrhage.

The diagnosis is suggested by visualization of an intrauterine gestational sac or decidual reaction located high in the fundus, that is not surrounded by more than 5 mm of myometrium in all planes.

An interstitial line sign - an echogenic line from the mass to the endometrial echo complex reportedly has high sensitivity (80%) and specificity (98%).

Management of interstitial ectopic includes methotrexate (either systemic or local), potassium chloride injection, conservative laparoscopic surgery, uterine artery embolization, cornuectomy or hysterectomy. The latter two are usually reserved for the emergency case or for failure of other methods.

Image contributed by: Dr Laughlin Dawes.