Persistent Hypoxia: Where Is the Shunt?

Case Report: A 57-year-old woman with end-stage renal disease presented with a 4-month history of progressive dyspnea. She had a history of polycystic kidney disease, failed renal transplant, and occluded left arteriovenous fistula. Both subclavian veins were thrombosed due to multiple hemodialysis catheter placements. An intrahepatic tunneled catheter was being used for dialysis. On admission, she was found to have an oxygen saturation of 80% on room air, with no evidence of pulmonary congestion on chest radiograph or pulmonary embolism on computed tomography (CT). A right-to-left shunt was considered in the differential diagnosis, and a transthoracic echocardiogram (Vivid e9, GE Healthcare, Pittsburgh, PA, USA; iE33, Philips Healthcare, Andover, MA, USA) was performed. The left and right ventricular systolic function was normal and no valvular abnormalities were noted. Injection of agitated saline in left upper extremity resulted in immediate, dense opacification of the entire left heart (Fig. 1). However, injection via the intrahepatic catheter demonstrated the bubbles to appear in the right heart (Fig. 2), with no evidence of patent foramen ovale. Chest radiograph obtained after placing a left internal jugular catheter (Bard Access Systems, Salt Lake City, UT, USA) showed an abnormal course with the catheter tip positioned in left upper chest (Fig. 3). Contrast venography was then performed to ascertain the position of the catheter, and it showed an obstructed superior vena cava (SVC) with the catheter tip positioned in the hemiazygos vein, and the contrast coursing through the bronchopulmonary plexus into the left atrium (Fig. 4), confirming our suspicion of a right-to-left shunt via systemic-to-pulmonary venous collaterals.