Incidental Detection of Situs Inversus Totalis Following Identification of an Unexpected Left-Sided Brachiocephalic Trunk on Carotid Duplex Ultrasound: A Case Report

Situs inversus totalis (SIT) is a challenging diagnosis, as failure to recognize the mirrored anatomy can result in complications during surgery, medical procedures, or emergency care. We present the case of a 60-year-old woman with a medical history of dyslipidemia who was referred for a carotid and vertebral artery duplex ultrasound ordered by the referring physician to evaluate subclinical atherosclerosis. The ultrasound unexpectedly showed that the brachiocephalic trunk was not identified on the right side, and a left-sided innominate artery was present, representing an unusual branching configuration. A subsequent contrast-enhanced computed tomography angiography (CTA) of the thorax and abdomen was performed, which revealed a complete situs inversus with mirror-image anatomy of the great vessels and thoracoabdominal viscera. The patient remained completely asymptomatic with no clinical consequences. This case highlights the importance of recognizing atypical vascular anatomy during routine imaging. The observation of an absent right brachiocephalic trunk on a standard Doppler study served as an unusual clue leading to the recognition of mirror-image anatomy.