Application of left lateral hepatolithiasis classification in minimally invasive hepatectomy

Left lateral hepatolithiasis is the most common subtype of intrahepatic bile duct stones. Although minimally invasive left lateral sectionectomy (MLS) is widely applied, postoperative stone recurrence remains frequent, particularly in the B4 bile duct. This study aimed to evaluate the clinical value of a classification based on B4 bile duct orifice involvement and to explore optimal minimally invasive surgical strategies. A retrospective analysis was performed on 238 patients with left lateral hepatolithiasis who underwent minimally invasive surgery between January 2015 and October 2024. Patients were classified into B4 type (stones compressing or obstructing the B4 bile duct orifice) and Non-B4 type. Perioperative outcomes, postoperative complications, stone recurrence, and long-term outcomes were compared. Subgroup analyses were conducted in B4-type patients undergoing MLS or conversion to middle hepatic vein-guided anatomical left hemihepatectomy combined with transhepatic lithotomy (MATL). Logistic regression analyses were used to identify independent risk and protective factors. Compared with the Non-B4 group, B4-type patients had longer operative time, greater blood loss, and significantly higher rates of bile leakage and stone recurrence. Multivariate analysis identified B4 bile duct orifice involvement as an independent risk factor for postoperative bile leakage (OR 16.58, p < 0.001) and stone recurrence (OR 30.87, p < 0.001). Conversion to MATL was an independent protective factor against bile leakage (OR 0.04, p = 0.003) and stone recurrence (OR 0.10, p = 0.003). In B4-type patients, MATL was associated with lower complication and recurrence rates without increasing perioperative risk. Left lateral hepatolithiasis involving the B4 bile duct orifice represents a more complex subtype with higher surgical risk and recurrence potential. Individualized surgical planning based on detailed preoperative imaging and intraoperative findings is essential. MATL may be a valuable option in selected B4-type patients.