Anatomy of the vasculature supplying hepatobiliary structures and celiac trunk branching patterns in the Thai population

The Institutional Review Board of the Faculty of Medicine, Chulalongkorn University, approved the protocol for the present study (IRB No. 093/61). The branching patterns of the CT and the origin of hepatic and cystic arteries were observed in cadavers of Thai adult volunteer donors during anatomical dissection classes of medical students. We included 100 formaldehyde-fixed cadavers (52 male, 48 female) without a history of abdominal surgery. Their ages were ranging from 34 and 99 years. During abdominal dissection, the abdominal vasculatures were observed in 3 aspects; first, the branching pattern of the CT; second, the origin of the RHA and LHA including their courses; and third, the origin of the CA and its relation to the common bile duct (CBD) and common hepatic duct (CHD). The data were recorded and observations are reported as percentages as appropriate.

The AA is the main arterial supply of intraabdominal organs. There are 2 primitive dorsal aortae in the human embryonic period, which fuse together at the end of fourth week and become the origin of descending aorta. Each primitive dorsal aorta gives rise to multiple of vitelline arteries. After fusion of the primitive dorsal aortae, the vitelline arteries mostly disappear and the rest of them become the origins of thoracic and abdominal arterial supplies (CT, superior mesenteric artery, inferior mesenteric artery) [15]. Variations of abdominal vessels may occur during the embryogenesis due to the persistence or incomplete fusion of some primitive vessels or other factors, such as the malrotation of intestines [1].

The most common branching pattern of CT (Type II) is the classical type with 3 branches. This finding resembles that of previous reports for various ethnicities [3, 4, 5]. The incidence of an LGA arising from the AA in Type I (1%) was less than that reported previously [7, 8]. Other origins of the LGA are also reported as the SA and CHA [9]. The incidence of CHA arising from SMA in Type III (1%) from this study is similar to that of previous reports [16, 17, 18, 19]. According to Adachi’s and Michels’ classifications, similar patterns were reported as gastrosplenic trunk and splenogastric trunk with CHA arising from SMA [8, 9]. These classifications did not indicate the origin of DPA from CT. Type IV was the other type that had 3 branches, the SA, CHA and LtIP from CT, and was found in 1 case. The inferior phrenic artery was previously mentioned as common inferior phrenic trunk arising from splenogastric trunk not directly from CT [3]. Type V was noted in 6 cases and was the second most common type in this study. The rRHA was the additional branch of this type. There was 1 case with an SGA arising from the CT as an additional branch.

Normally, the hepatic arterial system starts with the CHA from the CT and then, the CHA gives rise to the PHA. The PHA ramifies into the RHA and LHA, supplying each lobe of the liver. The classification of RHA and LHA in the present study was based on their origins and was categorized into 4 patterns according to the characteristic of each branch. However, from earlier studies [16, 17, 18, 19, 20, 21], the classifications of the 2 arteries (RHA, LHA) and their variation patterns were based on Michels’ criteria [13]. In Michels’ classification, the RHA and LHA were not analyzed separately. By contrast, the present study analyzed the variations of RHA and LHA individually. The incidence of normal pattern of RHA and LHA was lower than previous cadaveric and radiological reports in the Thai population [16, 17, 18, 19], but higher than that reported by Michels and lower than that reported by Hiatt et al. [13, 20]. The incidence of the rRHA + aRHA and rLHA + aLHA was 3 times that reported by Hiatt et al. [20]. This inconsistency was probably due to the different definition used for “replaced hepatic artery”. Hence, we included the hepatic artery originated from CHA as the rRHA or rLHA, while the study reported by Hiatt et al. classified the hepatic artery from the CHA as the normal RHA and LHA [20]. Variations in origin of replaced and accessory RHA and LHA were noted in the Thai population [16, 17, 18, 19]. From previous data, the most common origin of the rRHA was from the SMA (about 3.2%–13%) [13, 17, 18, 19]. However, in the present study the rRHA was from the CHA (13%), the SMA (9%), and the CT (8%). Moreover, from the present study, the rLHA was found in 31% of individuals, and originated from the CHA (30%) and the LGA (1%). By contrast, in previous studies, the origin of rLHA was solely from the LGA, which was confirmed by embryogenesis [21]. The incidence of an aRHA and an aLHA resembled that in a previous report of Thais [16], but was lower than that reported for individuals with other ethnicities [13, 20]. The origins of these arteries were from the CHA, SMA, and AA for the aRHA, but from the CHA and LGA for aLHA (Table 2) as consistent with previous reports [13, 16, 20].

The present study analyzed the CA in cadavers from Thai adults in 3 aspects: (1) the type of CAs, (2) the origin of the CA, and (3) the relation of the CA to the CBD and the CHD. The incidence of a single CA and of a double CA was consistent with that in previous reports, but the existence of a double CA was less [13, 14, 16, 22]. The most common origin of the CA from the RHA (79%) in the present study was similar to that reported previously [14, 22, 23]. The second most common origin of the CA was from the rRHA (13%). The other origins of the CA were from the aRHA, LHA, CHA, PHA, or GDA. The origin of the CA from the SMA was reported previously for a Thai population [22] and in studies of individuals with other ethnicities [14, 23].

The relationship of the CA to the CBD and CHD were classified into 2 types. Typically, the CA ran within cystohepatic triangle and coursed posteriorly to the CBD and CHD [13, 14, 22], which was also observed 59% (Table 4) of individuals in the present study. In cases of double CA, both arteries might pass anteriorly, posteriorly, or separating them.