Prenatal Detection of a Right Atrial Echogenic Mass: A Case Report of Hypertrophic Crista Terminalis

Background and Clinical Significance: The crista terminalis (CT) is a fibromuscular ridge located on the posterolateral wall of the right atrium, formed by the junction of the sinus venosus and the primitive right atrium. A hypertrophic or prominent CT (HCT) refers to a thickened or conspicuous configuration of this normal anatomical structure. In prenatal ultrasound (US) and/or echocardiographic assessments, HCT can mimic a right atrial mass, such as a tumor or a thrombus. Case Presentation: Herein, we describe a case of a fetal right atrial echogenic mass detected at 32 weeks, which remained stable through gestation and was confirmed postnatally as a likely HCT. No hemodynamic compromise, growth, or pathological sequelae were observed. Conclusions: Our case reinforces the importance of including atrial structural variants in the differential diagnosis of intracardiac masses, particularly when features favor stability and low risk. Serial imaging, avoidance of premature invasive measures, and careful counseling are key to appropriate management.