Cholecystitis is an inflammation of the gallbladder that is usually caused by gallstones obstructing the cystic duct and causing bile stasis. This leads to irritation, infection, and eventual necrosis of the gallbladder wall. Gallstones form due to factors like cholesterol, bilirubin, calcium salts, and may be pigment, cholesterol, or mixed types. Complications include biliary colic, acute and chronic cholecystitis, cholangitis, pancreatitis and cancer. Diagnosis involves imaging like ultrasound and HIDA scan, while treatment consists of laparoscopic cholecystectomy to remove the gallbladder.