Anomalous middle hepatic artery in laparoscopic cholecystectomy: Wolf in sheep's clothing.

Laparoscopic cholecystectomy is a simple but dangerous operation. The complex anatomy and frequent anomalies of the hepatic arterial and biliary system are often a shocking surprise to the laparoscopic surgeon. When these vital structures cannot be identified correctly, potentially crippling serious vascular and biliary injury can occur. A very rare case of middle hepatic artery encountered in the Calot's coursing over the gall bladder and travelling extraparenchymal into segment IV is reported. Identification and preservation of the middle hepatic artery is essential to prevent the possibility of hepatic artery thrombosis and to avoid ischemic cholangiopathy of segment IV duct. A comprehensive understanding of the hepatic arterial and biliary anatomy of the liver will empower laparoscopic surgeons to avoid crippling vascular and biliary injury.

A young lady, aged 35 years, was admitted with a diagnosis of symptomatic gallstonedisease for laparoscopic cholecystectomy. Review of her history revealed that she was suffering from biliary colic for the past 1 month. There was no history of jaundice, cholangitis or pancreatitis. She was a healthy lady with no comorbid illness or previous surgery. Her bilirubin, alkaline phosphatase and liver enzyme levels were within normal limits. Ultrasound of the abdomen showed multiple gallstones, gall bladder wall thickness measured as 3 mm and common bile duct measured as 6 mm. There were no features of acute cholecystitis. The patient was taken up for elective laparoscopic cholecystectomy. Closed pneumoperitoneum was created and laparoscopic dissection of Calot's proceeded. Cystic duct and artery were isolated. When the presumed cystic artery was dissected, it was found to be coursing anteriorly in the gallbladder fossa up until the midpoint of the body of the gallbladder, where it took an acute turn to run horizontally over segment IV (red arrows) and entered into the parenchyma in segment IV [Figure 1]. What appeared to be the cystic artery was the artery to segment IV or the middle hepatic artery. On further dissection, the cystic artery was found to be arising from the middle hepatic artery. Though the structure remained strange to many members of the team, it was identified by senior members as the middle hepatic artery. The vessel was carefully excluded and cholecystectomy completed.

Figure 1

Laparoscopic view of anomalous middle hepatic artery—red arrows. Divided cystic artery—white arrow

Recognition of vascular and biliary anatomy will empower surgeons to avoid dangerous biliary and vascular injury. The incidence of vascular injury during cholecystectomy has been estimated to be 7% in an autopsy series and the incidence increases to 12–39% when a concomitant biliary injury is present.[1] Couinaud describes that the liver during development is supplied by three main arteries.[2] The left gastric artery supplies the left lateral segment, the common hepatic artery supplies the paramedian segment and the superior mesenteric artery supplies the right lateral segment. Michel et al.[3] have thoroughly studied the vascular anatomy of the liver and classified the arterial supply to the liver. The most commonly encountered is the anomalous right hepatic artery (RHA). The artery to segment IV is called the middle hepatic artery as well. Suzuki et al.[4] reported that the artery was a branch of the left hepatic artery in 54%, RHA in 34% and the bifurcation of proper hepatic artery (PHA) in 8% and direct branch from common hepatic artery in 8% of cases. Jin et al.[5] reported that middle hepatic artery (A4) may course intrahepatically or extrahepatically. In addition, he noted that the middle hepatic artery has a wandering course. Based on the origin of vessels, he classified the dangerous types of segment IV artery variations into four types. Of these types, RHA type and the PHA type and the dual type may be encountered in the Calot's during laparoscopic cholecystectomy. Jin et al. additionally stressed on the importance of preserving the artery, as injury could increase the chance of hepatic artery thrombosis and result in ischemic cholangiopathy of segment IV bile duct.

Although, the clinical consequence of injury to the middle hepatic artery could be minimal, it is important to identify every structure that is not coursing into the gallbladder and to preserve it. The bile duct is supplied exclusively by the arterial system and arterial supply becomes the predominant source of inflow to the liver, especially when the portal venous supply is compromised. Furthermore, misidentification of vessels could lead to misjudgement of biliary structures and could lead to disastrous vasculobiliary injury. Every laparoscopic surgeon should develop a thorough understanding of the complex biliary and vascular anatomy of the liver before venturing into laparoscopic cholecystectomy.

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