As in many medical conditions, the most important part of making the diagnosis of gallbladder disease is the patient’s history and physical exam. If gallstone problems are suspected, sometimes routine liver blood tests are ordered as well as certain radiologic imaging studies. Abdominal ultrasound is the most commonly used tool to evaluate the gallbladder. Ultrasound is approximately 95% effective in diagnosing gallstones while they are in the gallbladder, but it is not very helpful for typically evaluating the common bile duct. Ultrasounds can also be helpful in determining whether there is evidence of cholecystitis by evaluating the thickness of the gallbladder wall, which typically increases with inflammation and infection. CAT scans can sometimes be used, but they are not as accurate as abdominal ultrasound. A nuclear medicine test referred to as a HIDA scan is sometimes helpful to tell us how the gallbladder is functioning and whether or not there is evidence of obstruction of the cystic duct, which drains the gallbladder or the common bile duct. An endoscopic tool sometimes used is an endoscopic ultrasound (EUS), which can sometimes be very helpful to evaluate the common bile duct, pancreas, and even the gallbladder. When there is evidence of bile duct obstruction, another endoscopic test referred to as ERCP (endoscopic retrograde cholangiopancreatography) is sometimes used to access the common bile duct and extract stones if they appear to be stuck in that area.