Unguarded tricuspid orifice---a rare cause of fetal right atrial dilatation with characteristic color doppler sign: Case report with review of literature.

The anatomic causes for fetal right atrial dilatation with tricuspid regurgitation include Ebstein anomaly, tricuspid dysplasia, unguarded tricuspid orifice, and Uhl anomaly. Unguarded tricuspid orifice is characterized by complete or partial agenesis of the tricuspid valvular and subvalvular structures. It is commonly associated with pulmonary atresia. Its prenatal diagnosis is usually associated with unfavorable prognosis. We present a prenatally diagnosed case of fetal unguarded tricuspid orifice with description of its diagnostic workup, along with a review of literature, to enhance the understanding of this rarely reported entity. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 45:370-374, 2017.