Development of a novel difficulty scoring system for laparoscopic liver resection procedure in patients with intrahepatic duct stones

Table 2 Independent factors predicting surgical difficulty by multiple linear regression

Independent variables	P value
Location of stones	0.002
Number of stones ≥ 3	0.037
Stone located in the bile ducts of several grades
Primary bile duct	0
Secondary bile duct	0.022
Tertiary bile duct	0.004
Previous biliary surgery less than twice	< 0.001
Distal bile duct atrophy	< 0.001