Gallbladder wall thickness of 4mm belongs to the thickening of gallbladder wall, which is an abnormal manifestation. The gallbladder is one of the organs of the human body, mainly responsible for the concentration and storage of bile. The wall of the gallbladder is generally divided into 3 layers, including the mucosa, submucosa, muscular layer and plasma membrane layer. Under normal circumstances, the wall of the gallbladder is smooth, with a thickness of 1-2 mm, mostly 1 mm, and if the thickness of the wall exceeds 4 mm on ultrasound or CT, the wall of the gallbladder is thickened. Common causes of gallbladder wall thickening include gallbladder disease, liver disease and other diseases. Gallbladder diseases mainly include cholecystitis, gallbladder stones, gallbladder polyps, gallbladder adenomyosis, etc. Liver diseases mainly include cirrhosis, hepatitis, intra- and extra-hepatic bile duct stones, etc. Other types of diseases include gastrointestinal disorders such as Crohn’s disease, duodenal papillary diverticulum, etc., and hemolytic anemia. If the gallbladder ultrasound or CT suggests thickening of the gallbladder wall, it is recommended to consult a doctor in time to clarify the cause of the disease and carry out targeted treatment or therapy.