Intrahepatic bile duct stones: 1. Cholesterol stones: High risk factors include female, obesity, pregnancy, advanced age, use of birth control pills and hormone replacement therapy. 2. Cholestatic stones: High-risk factors include chronic hemolysis, cirrhosis, biliary tract infection, parasites, and other related factors. Pathological changes: Bile duct obstruction. Biliary duct inflammation. Bile duct cancer. Clinical symptoms: Abdominal pain, fever, jaundice, etc. Treatment: Drugs: Ursodeoxycholic acid (for primary cirrhosis, prevention of gallstones induced by rapid weight loss due to dieting, etc.). Surgery: including choledochotomy for stone extraction, biliary-intestinal anastomosis, hepatectomy. Residual stone management (about 20-40%): choledochoscopy (stone retrieval after 6-8w postoperative).