Except in Budd-Chiari syndrome, alternative drainage pathways have been described rarely. The aim was to describe the alternative collaterals pathways due to tumor hepatic vein (HV) confluence obstruction and its impact in the setting of liver resection.

Between 2006 and 2014, preoperative CT scans of 41 patients resected for malignant tumor(s) compressing the HV confluence were assessed for the presence of accessory veins and collateral veins. A 2:1 matched control group was used for comparison of intraoperative outcomes.

Intrahepatic collaterals were observed in 28 (68%) patients, mostly between segments 3/4b and 5/4b, and subcapsular collaterals were observed in 12 (29%) patients. Patients with isolated right HV obstruction and with an accessory right HV present had fewer collateral pathways develop than patients without (6 of 10 patients [60%] vs 18 of 19 [95%]; p = 0.036). Segment 1 hypertrophy was present in only 6 (15%) patients. Compared with the control group, there was a significant increase in blood loss (900 mL [range 100 to 3,500 mL] vs 500 mL [range 100 to 2,600 mL]; p < 0.001), transfusion requirements (71% vs 15%; p < 0.001), and vascular clamping (hepatic pedicle: 85% vs 72%; p < 0.001, inferior vena cava: 41% vs 11%; p < 0.001) in case of HV obstruction.

Development of collateral pathways is not fortuitous and depends on the number of HVs involved and pre-existing accessory veins. The increased blood loss observed in patients with collaterals leads to consider specific vascular clamping.