Hepatic artery anatomy is highly variable (Michels classification, 10 types). Standard anatomy (type I, present in 55-75% of individuals): proper hepatic artery from the celiac trunk divides into right and left hepatic. Common variants: replaced right hepatic artery arising from the SMA (present in 11-21%); replaced left hepatic artery arising from the left gastric artery (present in 11-14%); replaced common hepatic artery from the SMA (present in 2.5%); and accessory variants alongside the replaced vessels.
Replaced hepatic artery variants are critical in hepatic surgery (right hepatectomy, liver transplantation), Whipple pancreaticoduodenectomy, and gastric surgery. A replaced right hepatic artery from the SMA runs in the hepatoduodenal ligament posterior to the CBD and portal vein — its inadvertent ligation during cholecystectomy or biliary surgery causes right lobe ischaemia. Pre-operative CT angiography of the celiac and SMA axes identifies hepatic artery variants before planned surgery. In liver transplantation, variant hepatic arteries require arterial reconstruction to ensure adequate graft perfusion.
A replaced right hepatic artery running posterior to the bile duct in the hepatoduodenal ligament may be mistaken for the cystic artery during cholecystectomy and ligated, causing right hepatic lobe ischaemia; pre-operative awareness of hepatic artery variants from CT angiography and careful hepatoduodenal dissection before any vessel division prevents this complication.
