A contrast dye CT scan is not the most reliable method of finding gallstones in bile ducts, according to University of Michigan Health System. Magnetic resonance cholangiopancreatography, or MRCP, and the endoscopic ultrasound are both better at detecting these stones.
While bile duct stones are sometimes visible on a CT scan or ultrasound, an MRCP produces very detailed images of the bile ducts. In addition, an MRCP provides clear views of the pancreas, liver and gallbladder. Intricate images of the digestive tract are obtained by way of the sound waves resulting from the ultrasound aspect of the procedure. An ERCP, or endoscopic retrograde cholangiopancreatography, is the preferred method of stone removal, explains University of Michigan Health System.