The central uterine cavity echo: a useful anatomic sign in the ultrasonographic evaluation of the female pelvis.

The frequency with which the central uterine cavity was seen during gray-scale ultrasonography was evaluated both retrospectively (100 patients) and prospectively (20 patients). In the retrospective study, the echo was seen in 90% of patients; in the prospective study it was demonstrated 100% of the time. Of 30 patients with intrauterine pregnancies between three and twelve weeks fetal age, the echo was not seen on any scan. The demonstration of this echo can be diagnostically useful in excluding an intrauterine pregnancy or identifying the uterus when confusing pelvic pathology is present.