Cholangitis: This is often considered the most common cause of CBD (common bile duct) stricture, particularly in the context of recurrent or chronic inflammation. Cholangitis can lead to scarring and narrowing of the bile duct.

Trauma: Traumatic injury to the bile ducts, either from external causes like accidents or iatrogenic causes such as surgical complications, can lead to stricture formation due to healing and scarring.
Malignant causes: Tumors, either primary (like cholangiocarcinoma) or secondary (metastatic), can cause strictures by invading the bile duct wall.

Primary sclerosing cholangitis (PSC): Although less common, PSC is a chronic liver disease that leads to scarring, inflammation, and destruction of the bile ducts inside and outside the liver. It can cause multiple strictures and has a significant association with the development of cholangiocarcinoma.
Hepatic artery aneurysm or pseudoaneurysm: These can cause extrinsic compression or erosion into the CBD, leading to stricture or obstruction, and are potentially life-threatening if ruptured.

Congenital anomalies: Conditions like choledochal cysts can sometimes present with strictures, although these are typically identified earlier in life.
Parasitic infections: Certain parasites, such as Ascaris lumbricoides, can cause biliary obstruction and potentially lead to stricture formation, although this is more common in endemic areas.
Ischemic strictures: These can occur due to reduced blood flow to the bile ducts, which might be seen in conditions like vasculitis or after certain types of surgical procedures.