BACKGROUND Persistent left superior vena cava (PLSVC) is a congenital anomaly with an estimated incidence of 0.3-0.5% in the normal population. Its usual discovery is often made by an abnormally positioned catheter inserted in the left subclavian or left jugular vein. In this situation, an easy bedside approach to confirm an anatomic variation in the central venous system is helpful. In the majority of cases, the PLSVC drains to the coronary sinus. OBJECTIVE To describe the contribution of bedside echocardiography in diagnosing the unstable patient in whom there is suspicion of a PLSVC. CASE REPORT A 29-year-old man underwent an emergent laparotomy for multiple intra-abdominal abscesses. Postoperatively, after insertion of a central line catheter through the left subclavian vein, a chest X-ray study showed the tip of the catheter in a left paramediastinal position instead of crossing the midline to the superior vena cava. A PLSVC was suspected. The patient was hemodynamically unstable; therefore, a bedside non-invasive confirmation of the diagnosis of PLSVC was preferred. A transthoracic echocardiography study was performed after injection of agitated saline (creating air-filled microbubbles by shaking saline solution in a syringe), which showed that the coronary sinus was opacified, confirming the diagnosis of a PLSVC. CONCLUSION In this brief report, we describe the contribution of echocardiography to the diagnosis of a PLSVC. Echocardiography is a reliable and easy diagnostic tool that allows a bedside approach in a patient in whom there is suspicion of a PLSVC, without administration of radiographic contrast.