Acute cholecystitis is a pathological entity of inflammatory origin, with a high prevalence worldwide. The term cholecystitis defines an inflammation of the gallbladder. Although most people with gallstones do not have symptoms and will not go on to develop cholecystitis, cholecystitis occurs most commonly due to blockage of the cystic duct with gallstones (cholelithiasis). In this book, Chapter One provides a contemporary review of acute cholecystitis (AC). Chapter Two examines the diagnosis and treatment options for AC. Chapter Three focuses on the diagnostic work-up of patients with AC. Chapter Four discusses early and delayed cholecystectomy as a treatment for AC. Chapter Five examines the current literature as it pertains to the management of patients who present with Grade II (moderate) acute cholecystitis, specifically looking at the timing of operation and the appropriateness of drainage procedures. Chapter Six reviews cholecystitis in systemic lupus erythematosus.