Gallstones Gallbladder stones are a common disease of the biliary system. With the development of the economy and changes in people’s dietary structure, the incidence of gallbladder stones has shown a significant increase. The first choice of examination for gallstones is ultrasound, for patients with gallstones found by ultrasound, they will often undergo CT examination to further confirm the diagnosis, but if a patient is suspected of having gallstone disease, is it possible to just do CT examination? The answer is no! The main symptoms of cholelithiasis are right upper abdominal pain and jaundice, and complications of cholangitis may include high fever. The pathological basis of cholelithiasis is the precipitation and agglomeration of bile pigments, cholesterol, mucus substances and calcium salts in the bile under the influence of bile stagnation and biliary tract infection. Those occurring in the gallbladder are called gallbladder stones and those occurring in the bile duct are called bile duct stones, collectively known as cholelithiasis. Gallstones can be classified into 3 types according to their chemical composition: cholesterol stones: more than 80% cholesterol; bile pigment stones: less than 25% cholesterol; mixed stones: 55% to 70% cholesterol. Positive stones are stones that are not easily transmitted by X-ray and have a high density; negative stones are stones that are easily transmitted by X-ray and have a low density. The CT scan performance of gallstones correlates with the density of their chemical composition, and their CT values are negatively correlated with cholesterol content and positively correlated with bilirubin and calcium content. Therefore, low-density stones found on CT scan can be determined to be primarily composed of cholesterol. Gallstones can be located in the gallbladder or bile ducts, and their symptoms are related to the size and location of the gallstones and the presence or absence of concomitant cholecystitis. Direct signs of intrahepatic bile duct stones manifest as high-density intrahepatic images, and multiple intrahepatic bile duct stones show a cast pattern. Intrahepatic bile duct stones should be distinguished from intrahepatic calcifications, which have higher CT values, the former often have CT values of about 100 HU, and the latter have no intrahepatic biliary dilatation, the former are often multiple and still visible at multiple levels. Indirect signs of intrahepatic bile duct stones show dilatation of the intrahepatic bile ducts, while extrahepatic bile duct stones are seen above the obstructed segment. Ultrasound is superior to CT scan for the diagnosis of negative stones. The treatment of gallbladder stones by cholecystectomy may not only have a high rate of postoperative complications, but also damage the patient’s body function, which increases the risk of right hemicolectomy and even a 2% mortality rate. It is important to achieve a better result through conservative treatment, especially for patients who are in poor physical condition and cannot tolerate surgery or who want to preserve their gallbladder. When gallstone disease is detected by ultrasound, it should be further examined by CT. Using spiral CT scan, it is possible to determine not only the number and size of stones, but also the density of stones and their composition, and to provide new treatment directions for low-density cholesterol stones, small stones with low calcium salts, and isodense stones with negative CT, such as cholesterol stones with ultrasound lithotripsy or chemical lithotripsy. With the popularization of medical imaging equipment, CT plain scan will provide greater value of clinical imaging data.