Unexpected Internal Jugular Vein Agenesis During Central Venous Cannulation: Implications for Ultrasound-Guided Access.

The right internal jugular vein (IJV) is the preferred site for central venous access due to its predictable anatomy and direct course to the superior vena cava. Congenital agenesis of the IJV is exceedingly rare and may have significant implications during central venous cannulation. We present a 67-year-old male patient undergoing hepatic resection who required central venous access after failure of peripheral intravenous lines. Pre-procedural ultrasound of the right neck demonstrated the absence of the right IJV despite appropriate positioning. Further examination confirmed right IJV agenesis and compensatory dilation of the left IJV. Given the necessity of central access and hemodynamic monitoring, a multidisciplinary discussion was undertaken regarding the potential risks of cannulating the sole major cerebral venous outflow pathway. The left IJV was successfully cannulated under ultrasound guidance without complication. Postoperative imaging reconfirmed the absence of the right IJV. This case underscores the importance of routine ultrasound evaluation prior to central venous cannulation. Recognition of rare vascular anomalies such as unilateral IJV agenesis is critical to prevent arterial injury and to guide safe anesthetic decision-making.