Anatomical Variations of the Hepatic Artery: A Multicenter Cadaveric Study.

Surgeons rely on predictable anatomical roadmaps to safely navigate the human body. However, when it comes to the arterial supply of the liver, Mother Nature frequently deviates from the blueprint. Standard hepatic anatomy—where the common hepatic artery arises from the celiac trunk and divides into the right and left hepatic arteries—occurs in roughly 80% of people. For the remaining portion of the population, the vascular wiring takes alternative routes. Understanding these variations is no longer just an academic exercise for anatomists; it is a daily necessity in operating rooms. With the rise of split-liver transplantations, laparoscopic cholecystectomies, and aggressive pancreatectomies, cutting an unrecognized "accessory" or "replaced" hepatic artery can lead to catastrophic liver necrosis or biliary leakage.

Historically, anatomist N.A. Michels mapped these arterial pathways based on 200 cadaveric dissections, ultimately identifying 10 distinct types of hepatic arterial anatomy in 1966. Decades later, researchers like Hiatt simplified this into a streamlined six-category system. However, even with these established classifications, modern surgeons still occasionally uncover rare variations that simply do not fit into the standard Michels or Hiatt classes. To better map these vascular anomalies within our demographic, we initiated this multicenter study to evaluate the prevalence, types, and statistical patterns of hepatic artery variations.

Study Design and Setting

We designed a descriptive, multicenter observational cadaveric study. The primary dissections and data coordination took place at the Department of Anatomy at SCB Medical College and Hospital (SCB MCH), Cuttack, in collaboration with two affiliated regional anatomy centers.

Study Period

The study was conducted over a two-year period, from April 2021 to March 2023.

Specimen Collection and Dissection

We examined 150 adult human cadavers (formalin-fixed) allocated for routine medical dissection. The anterior abdominal wall was opened, and the lesser omentum was meticulously cleared. We traced the celiac trunk and the superior mesenteric artery (SMA) to identify the common hepatic artery, proper hepatic artery, and any accessory or replaced branches supplying the liver parenchyma.

Statistical Analysis

Data were tabulated and analyzed using SPSS Software. We utilized the Chi-square test to determine the statistical significance of relationships between anatomical variations and demographic factors like gender. A p-value of less than 0.05 was considered statistically significant.

During the 2023–2024 study period, 150 cadavers were successfully dissected and analyzed. The demographic breakdown is detailed in Table 1.

Table-1

Description: Table 1 outlines the demographic characteristics of the cadaveric specimens studied at SCB MCH and affiliated centers. The sample predominantly consisted of older male specimens, reflecting standard body donation patterns.

We categorized the observed arterial structures using the classic Michels classification system. Normal anatomy was the most common, but nearly a quarter of the specimens exhibited variations.

Table-2

Description: Table 2 illustrates the prevalence of hepatic artery variations according to the Michels classification. Type I (normal) is the vast majority, while Type III (a replaced right hepatic artery from the SMA) stands as the most common anomaly. To understand the nature of the extra blood vessels, we separated the anomalies into "replaced" arteries (where the normal artery is entirely absent and substituted by an anomalous one) and "accessory" arteries (an extra vessel present alongside a normal one).

Table-3

Description: Table 3 compares the incidence of replaced versus accessory hepatic arteries. Replaced right hepatic arteries represent the most frequent singular vascular anomaly encountered during dissection.

We tested whether the presence of a hepatic arterial variation had any statistical correlation with the gender of the cadaver.

Table-4

Description: Table 4 analyzes the distribution of normal versus variant anatomy by gender. With a calculated Chi-square p-value of 0.58, the data confirms that there is no statistical significance linking a patient's gender to the likelihood of possessing a variant hepatic artery. Finally, we tracked the source vessels that gave rise to the anomalous hepatic arteries to highlight exactly where surgeons should be looking for unexpected branches.

Table-5

Description: Table 5 shows the origin points for variant arteries. There is high statistical significance (p < 0.01) demonstrating that variant Right Hepatic Arteries overwhelmingly originate from the SMA, while variant Left Hepatic Arteries reliably originate from the Left Gastric Artery.

When operating in the upper abdomen, assuming a patient has "textbook anatomy" is a dangerous gamble. Our multicenter study at SCB MCH from 2023 to 2024 confirms that while most individuals (76.6%) feature standard Type I vascularization, nearly 1 in 4 people possess a notable arterial variation.

The most frequent anomaly we noted was the Type III variation—a replaced right hepatic artery (RHA) branching off the superior mesenteric artery (SMA)—found in 9.3% of our specimens. This closely aligns with broader global literature, which often cites Type III as the chief source of variant blood supply to the bile duct. From a clinical perspective, this specific variation is incredibly important. During a pancreaticoduodenectomy (Whipple procedure), a replaced RHA running behind the head of the pancreas is highly vulnerable to accidental ligation.

Our data also highlights the intricate nature of vascular embryology. The large number of variants can be traced back to the complex development of the vascular supply in the human embryo, as well as the normal caudal displacement of the liver during fetal development. Interestingly, we identified two cases (1.3%) that defied the traditional Michels classification entirely. These "Class 0" or unclassified variants serve as a stark reminder that even the most comprehensive anatomical textbooks cannot capture every quirk of human biology.

While our analysis showed no statistical significance regarding gender (p = 0.58), the source origins of the variations were highly predictable and statistically significant (p < 0.01): right-sided anomalies almost always stem from the SMA, and left-sided anomalies stem from the Left Gastric Artery.

The hepatic arterial system is highly variable. This multicenter study out of SCB MCH underscores that variant anatomy—especially a replaced RHA originating from the SMA—is a routine reality rather than a rare medical curiosity. We strongly advise that pre-operative imaging and intra-operative physical palpation of the hepatoduodenal ligament be standard practice for all upper abdominal surgeries to prevent inadvertent ischemic liver injuries.

1.       Michels NA. Blood supply and anatomy of the upper abdominal organs, with a descriptive atlas. Lippincott, Philadelphia. 1955.

2.       Michels NA. Newer anatomy of the liver and its variant blood supply and collateral circulation. Am J Surg. 1966;112:337–347.

3.       Hiatt JR, Gabbay J, Busuttil RW. Surgical anatomy of the hepatic arteries in 1000 cases. Ann Surg. 1994;220(1):50–52.

4.       Adachi B. Das Arteriensystem der Japaner. Vol. 2. Kaiserlich-Japanischen Universitat; Kyoto: 1928.

5.       Haller A. Icones anatomicae in quibus aliquae partes corporis humani delineatae proponuntur et arteriarum potissimum historia continetur. Vandenhoeck; Gottingen: 1756.

6.       Noussios G, Dimitriou I, Chatzis I, Katsourakis A. The main anatomic variations of the hepatic artery and their importance in surgical practice: review of the literature. J Clin Med Res. 2017;9(4):248–252.

7.       Rygaard H, Forrest M, Mygind T, Baden H. Anatomic variants of the hepatic arteries. Acta Radiol Diagn (Stockh). 1986;27(4):425-427.

8.       Koshariya M, Khare V, Songra MC, Shukla S, Gupta A. Anomalous anatomical variations of coeliac trunk: a cadaveric study. Cureus. 2021;13(10):e19108.

9.       Blumgart LH, Belghiti J. Surgery of the liver, biliary tract, and pancreas. 4th ed. Saunders Elsevier; Philadelphia: 2007.

10.    Tiedemann F. Tabularum arteriarum corporis humani. Muller; Carlsruhae: 1822.

11.    Flint ER. Abnormalities of the right hepatic, cystic, and gastroduodenal arteries, and of the bile-ducts. Br J Surg. 1923;10:509–519.

12.    Lipshutz B. A Composite Study of the Coeliac Axis Artery. Ann Surg. 1917;65(2):159–169.

13.    Morita M. Reports and conception of three anomalous cases on the area of the celiac and the superior mesenteric arteries. Igaku Kenkyu. 1935;9:159–172.

14.    Prakash, Rajini T, Mokhasi V, Geethanjali BS, Sivacharan PV, Shashirekha M. Coeliac trunk and its branches: anatomical variations and clinical implications. Singapore Med J. 2012;53(5):329–331.

15.    Abdullah SS, Mabrut JY, Garbit V, et al. Anatomical variations of the hepatic artery: study of 932 cases in liver transplantation. Surg Radiol Anat. 2006;28(5):468-473.