| Abstract|| |
Background: The hepatic arterial anatomy is aberrant in almost 33-41% of individuals. The variant arterial anatomy recognized during routine cadaveric dissection offers great learning potential. Such findings provide an alternative perspective to view common morphology and its structural and functional importance. These impart the concept of patient individuality and subsequent individualization of medical and surgical therapies. Adequate knowledge of normal and abnormal arterial anatomy is essential for peripancreatic surgery and liver transplantation. Aims of the study: To report on hepatic artery variations observed in the dissecting room and to find out the macroscopic pattern of varied human hepatic arterial vascularization by cadaveric dissection. Patients and Methods: Twenty human cadavers of caucasian origin were dissected to study the source and topographic pattern of hepatic arterial supply. Results: Nineteen cadavers exhibited typical hepatic arterial supply from the celiac axis. Only one female body out of twenty cadavers exhibited a dual arterial supply to all parts of liver and gallbladder. One artery originated from the celiac axis whereas the other was given off by the superior mesenteric artery. Conclusion: No doubt, aberrant hepatic vascularization should be assessed preoperatively by invasive and noninvasive techniques to avoid fatal complications, but we favour careful dissection over angiography as a means of defining the arterial anatomy.
Keywords: Celiac trunk, superior mesenteric artery, liver, cystic artery, abdominal aorta
|How to cite this article:|
Saeed M, Rufai AA. Duplication of hepatic artery. Saudi J Gastroenterol 2001;7:103-8
Hepatic arterial injury secondary to penetrating and blunt trauma is well documented  . Vascular injuries are the most lethal technical injuries encountered in laparoscopic cholecystectomy  . Injury to hepatic blood supply is more common in the presence of aberrant arterial anatomy. Preoperative knowledge of normal and variant arterial anatomy can lead to measures to preserve the vessels and avoid fatal injury  . The aberrant vessels can be identified on visceral angiography, dynamic contrast enhanced magnetic resonance imaging(DCEMRI) and/or spiral CT. In the detection of an aberrant vessel, DCEMRI has been shown to have a sensitivity of 89%, specificity of 100% and an accuracy of 97% 
A typical normal hepatic artery arises from the celiac trunk and divides into three main branches, the right hepatic artery entering the right lobe of liver, a left hepatic artery entering the left lobe and a middle hepatic entering the quadrate lobe of the liver  . When hepatic artery arises from a source other than the terminal end of the celiac trunk, it is considered an aberrant hepatic  . The aberrant hepatic artery may be accessory or replaced. The accessory to be interpreted only from the view point of origin, for functional consideration, all hepatic arteries are essential  . The term accessory hepatic is used only when the right or left hepatic artery coexist with a normal celiacal right or left hepatic, whereas the absence of normal right or left and its replacement by an aberrant vessel is termed as replaced right or left hepatic artery.
The variant anatomy of the celiac axis is very common. The main cause for aberrant morphology of the celiac axis is the frequency and diversity of origin and distribution of the hepatic arteries  . The hepatic arteries may arise from the abdominal aorta, the left gastric or the superior mesenteric arteries . The hepatic arterial anatomy is aberrant in almost 33-41% of individuals ,,, . The most common anomalies include, the right hepatic artery arising from superior mesenteric artery (25%) and left hepatic artery arising from the left gastric artery (25%)  . Anomalies of the common hepatic artery, usually a branch of the celiac trunk, are relatively uncommon  . However, Kadir et al., (1991) demonstrated angiographically a 5% incidence of the replaced common hepatic artery  whereas Woods and Traverso (1993) found the replaced common hepatic artery, branching off the superior mesenteric artery in 2.5% of the cases  . However no study has pointed out the existence of accessory common hepatic artery of celiac origin.
An aberrant hepatic artery may cause a potential error in the angiographic diagnosis of traumatic liver hematoma  . Adequate knowledge of peripancreatic arterial anatomy is essential for satisfactory resection of pancreatic tumors. Moreover the existence of aberrant hepatic arteries highlights the mode of development of liver during perinatal period  . Liver transplantation and peripancreatic surgery needs extensive, adequately based clear appreciation and knowledge of varied blood supply of liver. Over the last decade the armamentarium of diagnostic procedures used in preoperative evaluation of patients suspected of periampullary tumors has grown extensively. Now, visceral angiography, DCEMRI and/or spiral CT are used commonly for preoperative evaluation of patients suspected of periampullary tumors. Although these sophisticated techniques are very much useful in the detection of peripancreatic arterial anatomy, yet the macroscopic dissection of cadavers in the dissection room and per-operative dissection in the operation room, is still the easiest and most reliable method of studying the normal and variant arterial anatomy.
| Subjects and Methods|| |
We dissected carefully twenty white cadavers of caucasian origin (fifteen males and five females), aged between 45-65 years, randomly assigned to medical students for dissection over a two years period. We took the arduous task of dissection from origin to termination of all the major arteries supplying the billiary system. To study the variational anatomy of hepatic arterial supply, we decided to follow all the branches of celiac and superior mesenteric arteries, supplying the supramesocolic organs. Especially all hepatic vessels were painstakingly dissected from origin to ultimate distribution in the substance of liver.
We selected those bodies only, which were properly embalmed and having arteries fairly well injected with dye. In all instances the dissection of arteries and their sketches were completed before the students disturbed the topographic relations. The fine details of terminal ramifications of the regional arteries, especially of the cystic and hepatic arteries were worked out enblock. The measurements of length and external diameter of arteries were done by sliding vernier calipers.
| Results|| |
After a careful dissection of twenty cadavers, we analyzed the variational pattern of celiac axis, superior mesenteric artery and the source and distribution of hepatic arteries.
Celiac trunk: All cadavers exhibited classical (Hepatoleinogastric) pattern of celiac trunk's origin and distribution. In a study of twenty celiac trunks, the length of celiac trunk varied from 6-25mm and its width from 9-20mm [Table - 1]. The celiac trunk was constricted at its site of origin from the abdominal aorta. The distance on the aorta between the sites of origin of celiac and superior mesenteric arteries varied from 5-15mm. In eighteen cases splenic artery was the largest branch of celiac trunk, whereas two cases had common hepatic as largest branch. However left gastric was the first and smallest branch of celiac trunk in all cases.
Hepatic arteries: Except one, all cadavers exhibited three hepatic arteries, i.e., right, left and middle hepatic arteries for the right, left and quadrate lobes of the liver respectively. One case (5%) presented with six hepatic arteries, i.e., three normal, of celiac origin and other three accessory, arising from accessory common hepatic artery of superior mesenteric origin. Hepatic arterial variants are common but this is a unique case of duplication of common hepatic artery, arterializing all areas of liver and biliary tree. The width of accessory common hepatic artery (16mm) was relatively more than that of classical celiacal common hepatic artery (12mm). The accessory common hepatic artery routed to the portahepatus posterior to the head of the pancreas and portal vein, entered the right margin of hepato-duodenal part of lesser omentum, where it was lying medial to the common bile duct and anterior to the portal vein [Figure - 1],[Figure - 2], mimicking the normal gastroduodenal artery. The normal hepatic artery was placed further medial to it.
Cystic artery: In nineteen cases the cystic artery was single and arising from the right hepatic artery (15-cases), left hepatic artery (one case) and proper hepatic artery (3-cases), whereas one cadaver exhibited two cystic arteries, each arising from the normal right hepatic and accessory common hepatic arteries respectively, within callot's triangle.
Associated arterial anomalies: The same cadaver exhibited the replaced bilateral obturator artery, arising from external iliac artery and an anomalous left gonadal artery arising from the accessory left renal artery [Figure - 1]. The accessory left renal artery was comparable in size to the normal left renal artery but the left gonadal artery was much smaller than its right counterpart.
| Discussion|| |
Aberrant hepatic arterial anatomy occurs in 33-41% of reported literature ,, . The common hepatic artery is usually a branch of the celiac trunk  . This classical "Michels type -I" pattern with right and left hepatic arteries originating from the common hepatic artery (of celiac origin) occurs in about 55% of the population . Although the normal pattern of arterial supply of hepatic parenchyma and biliary tract is well described, there is a considerable variation in the relative contribution of normal and abnormal arteries to parenchyma and biliary tree in the presence of anomalies ,.
The replaced hepatic arteries (replaced right hepatic and replaced common hepatic arteries) usually do not occupy the same position in the hepatoduodenal ligament as the normally occurring hepatic artery. Those typically lie lateral to the portal vein behind the head of the pancreas and enter the lesser omentum posterolateral to the common bile duct , . In Michels 200 liver dissections, he found half of the replaced common hepatic arteries (RCHA) actually passed through the pancreatic substance while the other half passed posterior to it. In our case the accessory common hepatic artery never entered the pancreatic tissue. It was routing to portahepatus posterior to the head of pancreas and first part of the duodenum, thus mimicking the normal gastroduodenal artery in right margin of hepatoduodenal part of the lesser omentum.
As the branches of the hepatic arteries supplying the liver are essentially end arteries, therefore, in the context of a liver transplant, all anomalous arteries should be considered for preservation and revascularization if deemed large enough to be anastomosed to avoid ischaemal, paranchymal and biliary tract complications  . Although some collaterals exist in the liver capsule and hepatic ligaments, but the ligation of such an aberrant, accessory common hepatic artery during whipple procedure may lead to postoperative ischaemia of a part of liver, supplied by the said vessel. Moreover the existence of such an arterial variant in patients having liver metastasis, carries the risk of misperfusion of intra-arterial chemotherapeutic agents  . The intra-arterial chemotherapy technique for isolated, non resectable liver metastasis achieves complete perfusion of whole liver only in patients with classical arterial anatomy. Patients having variant arterial anatomy need vascular reconstruction prior to intra-arterial chemotherapy or the use of double port catheter pumps, for ideal, uniform perfusion .
The knowledge of hepatic arterial variations can be useful in the selection of donors for partial hepatic grafts in living related liver transplantation (LRLT)  . Such anomalies should be ruled out preoperatively  by angiography, Axial CT and/or DCEMRI  . LRLT is now performed as a means of alleviating the problem of graft shortage associated with cadaveric transplant. Hepatic arterial anatomy must be defined precisely to ensure optimal donor hepatectomy and graft arterialization  . The arterial configuration having aberrant LHA arising from left gastric artery is a major concern in LRLT, involving the use of left hepatic lobe as a graft . Moreover the preoperative knowledge of anomalous vessels is also helpful for modification of surgical approach . Arterial anomalies preserved and managed appropriately do not necessarily compromise graft outcome. Although no particular arterial configuration precludes the use of a donor liver as a whole or reduced graft, but more complications can be anticipated with complicated arterial reconstructions .
To our knowledge this is a unique case of aberrant hepatic arterial anatomy never reported before in English literature, where accessory common hepatic artery (of superior mesenteric origin) co-existed with a normal common hepatic artery of celiac origin, having a relatively bigger external diameter. Both common hepatic arteries duplicated the arterial supply not only to the liver but the whole biliary tree. The persistence of lower half of ventral longitudinal anastomosis between the 10 th to 13 th splanchnic (vitelline) arterial roots that normally disappear, may be the possible embryological explanation for this variability. Such variations may be attributed to the rotation of gut, caudal displacement of abdominal viscera and hemodynamic changes taking place during organogenesis and differentiation , However the present study has further added to the expanding list of variations in the hepatic arterial anatomy.
| Acknowledgments|| |
We thank Prof. Amonoo-Kuofi for his generous and critical advice, Mr. Veer for drawing illustration, Mr. Hanif Shahid for technical contribution and Mr. M. Moazam for his secretarial assistance.
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Department of Anatomy, College of Medicine, King Saud University, P. 0. Box 2925, Riyadh 11461
[Figure - 1], [Figure - 2]
[Table - 1]