The patient was a 62-year-old woman with a chest X-ray abnormality. Transthoracic echocardiography (TTE) showed a dilated right ventricle and right atrium and an enlarged coronary sinus (CS), but definite diagnosis was not possible. Using contrast-enhanced 64-slice multidetector computed tomography (MDCT), curved planar reconstruction along the CS showed a direct connection of the left atrium and CS, in addition to the CS to right atrium connection. Unroofed CS is a rare congenital cardiac anomaly that is difficult to diagnose with TTE alone. Our case indicates that MDCT is useful for determining structural information that cannot be obtained from TTE. &lt
Learning objective: The diagnosis of unroofed coronary sinus (CS) is often difficult because the ability of transthoracic echocardiography to visualize the posterior cardiac structure is limited. In our case, images from 64-slice multidetector computed tomography provided clear visualization of the morphology of the CS and permitted a definite diagnosis of unroofed CS.&gt