An Accessory Right Hepatic and Cystic Arteries Derived from the Superior Mesenteric Artery: A Cadaveric Case Report

Introduction

The native anatomic celiac trunk is reported to originate from the anterior surface of the abdominal aorta at the level of the twelfth thoracic vertebra. After its origin, the celiac trunk typically travels about 1–2 cm before dividing into 3 major branches: left gastric artery (LGA), splenic artery, and common hepatic artery (CHA). The LGA travels towards the lesser curvature of the stomach, supplying blood to the stomach and lower esophagus. The splenic artery runs towards the spleen, giving off numerous branches that supply the spleen, pancreas, and parts of the stomach. The CHA branches into the gastroduodenal artery and the proper hepatic artery (PHA), the latter of which then bifurcates into the left and right hepatic arteries (LHA and RHA). These LHA and RHA enter the left and right lobes of the liver, respectively.

While the native anatomic vasculature is most frequently reported, there remains a fair amount of anatomic variation reported in the literature [1–4]. Among the first to describe variations in celiac trunk vasculature was Michels, who created a commonly used classification system [1]. This classification system has been used by researchers and clinicians to categorize unique variations in published literature [4–6]. Awareness of the possible variation types has clinical utility for vascular surgery, interventional radiology, and transplantology [6–8]. Knowledge of patient anatomic variations may also help reduce the risk of iatrogenic injury. We present an uncommonly reported variant of an accessory hepatic artery branching from the superior mesenteric artery (SMA).

Case Report

During routine dissection of the foregut of a male cadaver, we identified some unique anatomic variations of the local vasculature. We initially removed the lesser omentum and opened its free border, exposing the portal triad. Next, 2 standard branches of celiac artery were identified: the LGA and CHA. The CHA coursed to the right and gave rise to the gastroduodenal artery before entering the free margin of the lesser omentum to become the PHA. The PHA ran in the free border of the right omentum to the left of the common bile duct. It then gave rise to the right gastric artery before bifurcating into the LHA and RHA (Figure 1A).

Upon further examination of the hepatic vasculature, we discovered an anomalous accessory right hepatic artery (ARHA) located behind the portal triad (Figure 1B). Interestingly, this accessory artery was a branch of the SMA. We then divided and reflected the stomach at the pyloric canal. The pancreas was also reflected at the neck to allow better visualization of the ARHA. We then noted that the ARHA traveled superiorly and laterally from the SMA but was hidden posterior to the portal triad (Figure 2A). Further removal of the portal vein revealed the ARHA traveled deep to the common bile duct before reaching the porta hepatis. Notably, the cystic arteries were derived from this anomalous branch, rather than the functional RHA (Figure 2B). This anomalous artery traveled a unique, separate, course from the RHA and the LHA. An illustration summarizing and comparing our findings to commonly reported native anatomy is shown in Figure 3. An additional noteworthy finding was the retroperitoneal location of the ARHA. The anomalous vessel ran posterior to the neck of the pancreas, duodenum, and portal triad at the same depth as the inferior vena cava (IVC). These findings suggest the ARHA was traveling posterior to the opening of the lesser sac.

Discussion

The celiac trunk originates from the embryonic aorta. During the fourth week of embryonic development, the ventral aspect of the aorta gives rise to paired dorsal aortae, which fuse and eventually form ventral segmental arteries. The paired vessels form the 3 major median vessels (the celiac trunk, superior mesenteric artery, and inferior mesenteric artery) [9,10]. The exact course of hepatic arterial development is complex and poorly understood; however, it may be related to persistence of embryologic right and left hepatic arteries, which typically obliterate [11,12].

There are many reported variations in the configuration of the celiac trunk, most typically classified according to categories by Michels and later by Hiatt [1–3]. Our case most closely resembles Michels’s type 6 (accessory RHA with LHA and middle hepatic; though with a typical RHA rather than a middle hepatic artery in this case) and Hiatt’s type 3 (accessory RHA from the SMA). A paper by López-Andújar and colleagues added 2 additional variations to the existing 10 commonly reported variations originally published by Michels et al [1,4]. Considering these 3 existing classification systems, our case most resembles a Lopez-Andújar Type 6, in which the ARHA arises from the SMA, but the LHA and RHA arise from the PHA [4]. This type of variation is infrequently reported, comprising only 7 (0.6%) of the 1081 subjects in the Lopez-Andújar paper. Further, to the best of our knowledge, this is the one of the first reported cases of a retroperitoneal ARHA, as most ARHAs rather travel near or through the head of the pancreas [13]. Given the infrequency of this variant, it remains important for physicians to be mindful of potential deviations, even from those published in extant literature, to provide optimal care.

Knowledge of anomalies in celiac trunk artery formation is important for a multitude of treatment and imaging modalities. Awareness of variations may have unique utility for surgeons and interventional radiologists, as their knowledge is important for complete treatment and mitigation of iatrogenic vascular injury [4,14]. Identification of abnormal hepatic vasculature is especially essential in pancreaticoduodectomies, where aberrant RHAs may increase bleeding risk [13,15]; in resection of peripheral hepatocellular carcinomas, especially where segmental or hemihepatic vascular clamping is used [16–18], and in laparoscopic procedures where vision is limited [19–21]. Additionally, retroperitoneal ARHAs are very infrequent and may confer additional risk if their unique course if not identified.

Studies have reported that knowledge of these variations may be applicable for interventional radiologists utilizing trans-arterial chemoembolization and emergency angiography [6,14,22], and there may be implications for targeted delivery of mesenchymal stem cells for treatment of cirrhosis as well [23–25]. Procedures such as liver transplantation may greatly benefit from knowledge of hepatic artery variation, as watershed regions of each artery can change with differences in vasculature [4,5,7,8,26]. It is critical to consider all possible configurations of the hepatic vasculature for liver transplantation to appropriately manage each case individually [27–29]. Perez-Saborido et al found poorer survival rates in back-table reconstruction liver transplant patients with RHA variants arising from the SMA [30], but Lai et al presented a differing opinion on revascularization of aberrant arterial patterns [31].

Conclusions

In this case report, we describe an instance of an anomalous accessory hepatic artery arising from the SMA and exclusively supplying the cystic arteries. This artery followed its own unique path, separate from the RHA and LHA arteries. This case adds further depth to the growing understanding of hepatic artery variations. Clinicians should carefully consider hepatic artery anatomic variations when performing hepatobiliary surgery or imaging to mitigate iatrogenic injury and optimize patient outcomes. Future research should explore the prevalence of this specific variant, especially retroperitoneal ARHAs, and the implications and complications that may arise from such a finding in vivo.