CT, portal angiogram: A large tortuous vessel is seen connecting the portal vein to the caudal vena cava. This is an aberrant vessel which increases the diameter of the caudal vena cava more than two-fold. Shunt vessel measures approximately 6.3 mm at its widest point, approximately the same diameter as the caudal vena cava going through the diaphragm. There is no evidence of urolithiasis. There is no evidence of pleural free fluid. There is no evidence of intrathoracic abnormalities.