Infection of the biliary tract or cholangitis is a potentially life-threatening systemic disease that results from a combination of bile duct obstruction and infection. Choledocholithiasis is the most common cause of acute cholangitis.

Other important causes include benign and malignant bile duct strictures, instrumentation or surgery involving the biliary tree, and rare causes including infection with hepatobiliary parasites, acquired immune deficiency syndrome cholangiopathy, and recurrent pyogenic cholangitis.

Several mechanisms have been proposed to contribute to the pathogenesis of cholangitis, including bacterial ascension from the small bowel (ascending cholangitis), bacterial translocation through the bowel wall followed by hematogenous seeding, and bacterial contamination of portal blood.

The most common organisms responsible for cholangitis are enteric gram-negative bacteria including Escherichia coli and Klebsiella , and gram-positive bacteria such as enterococci. Infection with multiple bacteria and anaerobic organisms is common in elderly patients and those with abnormal postsurgical biliary anatomy.

In the absence of established diagnostic criteria, a combination of clinical features, laboratory tests, and imaging studies are used to accurately diagnose acute cholangitis.