Cadaver organ donors have been an excellent resource for studying vascular systems since precise anatomical details can be identified and assessed. From these studies over the past several decades, anatomical variations have been categorized into classification and modeling systems. These systems have been used as procedural guides and planning by anatomists, surgeons and interventional radiologists. This has helped to predict and strive for optimal surgical and clinical outcomes, as well as help reduce procedural complications associated with anatomical knowledge deficiencies. Aberrations of the celiac trunk have been studied quite extensively because it is generally prone to variations and because of its juxtaposition and contribution to the pancreas, liver, duodenum and hepatic biliary tree. Six of the common classification systems currently used by surgeons and interventional radiologists include those created by Lipshutz, Adachi, Morita, Uflacker, Hiatt and Michels. All six classification systems acknowledge the rare variant characterized by a common hepatic artery arising from the superior mesenteric artery, which is referred to as the replaced common hepatic artery or the celiacomesenteric trunk. This variant can have significant clinical implications owing to its proximity to the pancreatic head. As imaging modality advancements continue to evolve, it is expected that anatomical modeling will also likely enhance. We are entering a time when more centralized and cohesive arterial classification systems are needed to help further our understanding of vascular variant patterns.
Keywords: Celiac trunk variation, Michel’s classification; Replaced common hepatic artery
There are five main branches that arise from the abdominal aorta to supply the abdominal viscera. These include the Celiac Trunk (CT), Superior Mesenteric Artery (SMA), left and right renal arteries, and Inferior Mesenteric Artery (IMA). Organs of the foregut are supplied mostly by the CT, while the midgut and the hindgut are supplied by the SMA and IMA, respectively.  The normal anatomy of the CT includes three main divisions: the Splenic Artery (SA), Common Hepatic Artery (CHA) and the Left Gastric Artery (LGA). In most cases, the CHA then divides into the Gastroduodenal Artery (GDA) and the Proper Hepatic Artery (PHA). Variations of the CT have been studied quite extensively by anatomists and specialists in medical fields because of its juxtaposition and contribution to the pancreas, duodenum and hepatic biliary tree. Variations have been studied as early as the eighteen hundreds by Swedish scientist Albrect von Haller. Haller’s anatomical atlas, published in parts between 1743 and 1756, provides the first glimpse of CT variations.  Lipshutz, Adachi, Morita, Uflacker, Hiatt and Michels are among others who generated more recent models and widely utilized classification systems of CT aberrations. Understanding and elucidating these variations and patterns commonly seen in vascular anatomy can highlight anatomical intricacies and help with preoperative surgical planning. Michels model is perhaps one of the most widely used classification systems implemented by surgeons today. This model demonstrates that in a limited number of cases, the CHA branches off of the SMA, which has been classified as the Type IX CT variant . When the CHA arises from the SMA, it can be prone to injury, especially during cases involving Pancreatoduodenectomy (PD). This case and review aims to describe this variation to further our understanding of its surgical implications in performing procedures, such as PD.
During routine cadaveric dissection of sixty-five human donors in the 2020-2021 first-year medical gross anatomy course and 2021 graduate nursing advanced anatomy course at the Uniformed Services University of the Health Sciences (USUHS), a Replaced Common Hepatic Artery (RCHA) was identified on a 70-year-old White male patient with a cause of death of pneumonia. The postmortem cadaveric study revealed important anatomical variations arising from the abdominal aorta and more specifically, from the CT . The variations were then documented and subsequently compared to the normal expected variations reported in the literature. Table 1 provides a brief description of each variation included in Michels classification.  Figure 1 is a posterior view artistic rendering of the CHA coursing off the SMA with the CT in place giving rise to the LGA and SA (and note the absent CHA branch coming off the CT). Figure 2 is a cadaveric image providing a closer look at the CHA identified in this particular case, noting its close proximity to the pancreatic head and coursing behind the pancreas, which is the more common presentation of the RCHA variation. Figure 3 shows a cadaveric image indicating the unique RCHA path – coursing up from the pancreas and behind the portal vein. Figure 4 is a digital image representing the RCHA in this case; the path of the artery is clearly depicted.