Ultrasonographic "endometrial three-layer" pattern: a unique finding in ectopic pregnancy.

Although diagnostic ultrasonography is playing an increasing role in the investigation of the patient with suspected ectopic pregnancy (EP), it has significant limitations in the very early stages of pregnancy. By sonographically exploring the intrauterine echoes in 45 cases of documented EP, we demonstrated a unique pattern in 28 cases (62.2%). A well-defined spheric structure forming an endometrial three-layer (ETL) pattern was seen, probably formed by a midline echo between the two adjacent edematous proliferative layers of the endometrium, the latter resembling the late proliferative endometrium. In 17 patients with a proved EP (37.8%), the ETL pattern was not demonstrated. However, the ETL was not demonstrated in all 40 cases of early intrauterine pregnancy and all 50 cases of miscarriage. These findings suggest a 100% specificity and a sensitivity of 62.2% for the ETL pattern in the diagnosis of EP.