A deviant anterior portal vein in the hepatoduodenal ligament with aberrant origin of hepatic arteries directly from the celiac trunk: A case report of two patients underwent pylorus preserving pancreatoduodenectomy (PPPD).

ABSTRACT

INTRODUCTION: The portal vein (PV) originates behind the neck of the pancreas, where it is formed classically by the union of the superior mesenteric vein (SMV) and the splenic vein (SV) [1]. It courses upwards towards the liver in the free margin of the lesser omentum, the hepatoduodenal ligament, along with other structures of the portal triad, i.e. proper hepatic artery (PHA) and common bile duct (CBD) anterior to it [1]. The PV is found posterior to the PHA and CBD. The abdominal aorta perfuses abdominal viscera via three ventral branches celiac trunk (CA), superior mesenteric artery (SMA), and inferior mesenteric artery (IMA). The celiac trunk supplies the derivates of the foregut and is divided into the left gastric artery (LGA), splenic artery (SA), and common hepatic artery (CHA). The CHA, after its origin, is divided into the gastroduodenal artery (GDA) and PHA. After giving off the right gastric artery (RGA), the PHA bifurcates into the right and left hepatic arteries (RHA, LHA) [2]. IMPORTANCE This case report aims to share the rare variations in the anatomy of hepatoduodenal ligament structures to increase awareness and understanding among fellow surgeons which may reduce complications. CASE PRESENTATION We are reporting 2 cases in which during pancreaticoduodenectomy Portal vein was present anteriorly in the portal triad and the common hepatic artery was absent; instead, both the right and left hepatic arteries originated directly from the CA posterior to PV. This retro-portal origin of hepatic arteries directly from CA is not reported in Michel's classification of hepatic artery variations [3]. CLINICAL DISCUSSION: The confluence of SMV and SV posterior to the neck of the pancreas forms the PV. The portal vein runs upwards in the free edge of the lesser omentum. Anteriorly it is related to the CBD laterally and CHA anteromedially. Posteriorly it is related to the inferior vena cava (IVC), and PV is separated from IVC by epiploic foramen [4]. The overall reported incidence in the variation of the portal vein anatomy is 25%. Among all the variations seen, the anterior PV with posteriorly bifurcating hepatic artery is present in only 10 % of the cases [5]. There is an increased risk of hepatic artery anatomical variation in the presence of portal vein variants. Michel's classification [6] classified variations in the hepatic artery anatomy. In our cases, the hepatic artery anatomy was standard and was classified as Type 1. The bile duct was normal anatomic (lateral to the PV). Hence our cases are unique in describing isolated variant locations and courses. Detailed information about the anatomy of the portal triad and all possible variants can help reduce the incidence of iatrogenic complications during surgeries like liver transplants and pancreatoduodenectomies. Before the advancement of modern imaging techniques, the variations in the anatomy of the portal triad were clinically irrelevant and considered less significant. However, recent literature supports that variant anatomy of the hepatic portal triad can prolong the time of surgery and increase the risk of iatrogenic complications. The clinical relevance of variable hepatic artery anatomy has immense importance in hepatobiliary surgeries, including liver transplants where the viability of the graft depends on adequate arterial perfusion. In addition to that, in pancreatoduodenectomies, aberrant arterial anatomy with a reteroportal course is associated with an increased number of reconstructions [7] and bilio-enteric anastomosis disruptions since the CBD derives its blood supply from the hepatic arteries. Therefore, the imaging must be carefully interpreted with radiologists' help before surgical planning. As surgeons preoperative imaging is usually seen for the abnormal origin of hepatic arteries and vascular involvement in case of malignancies. "Eyes don't see what mind doesn't know", the anterior portal vein is a rare entity and should be considered while reviewing preoperative imaging for operative planning. In our cases, EUS and CT scans, both were done but we determined resectability on scans and abnormal origin (replaced or accessory arteries) only. Above mentioned findings were noted during surgery but now in every preoperative scan, we try to determine the presence of all possible variations including the reported ones. CONCLUSION: Detailed knowledge about the anatomy of the portal triad and all possible variants can help reduce the incidence of iatrogenic complications during surgeries like liver transplants and pancreatoduodenectomies. It also reduces the time of surgery. A careful review of all possible variations in preoperative scans with appropriate knowledge all anatomical variations helps avoid unpleasant events and hence, reduce morbidity and mortality.