Duplication of Portal Vein: Insights into Embryological Basis and Clinical Implications

Duplication of the portal vein (DPV) is an extremely rare anatomical variation, with only a few documented cases.[1] Understanding potential variations in portal venous anatomy is crucial for the early detection of developmental anomalies, particularly during assessments for liver transplantation, hepatic resection, and before catheter-based endovascular procedures. This knowledge aids in treatment planning and helps minimize iatrogenic complications. We present a case of incidentally discovered DPV.

A 42-year-old gentleman was being evaluated as a potential liver donor for his brother who was suffering from end-stage liver disease. Physical examination and laboratory tests were unremarkable. As part of the workup, he underwent a multiphasic contrast-enhanced computed tomographic (CT) scan of the abdomen. The portal venous phase images showed differential enhancement of the right and left lobes of the liver with two portal veins (PVs) entering the porta along the hepatoduodenal ligament ([Fig. 1]). One of the PVs was seen as continuation of the superior mesenteric vein (SMV) and coursed between the duodenum and pancreas to ascend to the porta hepatis and supply predominantly the right lobe of the liver (referred to as “mesenteric PV” later in the article). Another anastomotic branch originated from the SMV immediately caudal to the uncinate process to join the splenic vein (SV) posterior to the neck of the pancreas to form the other PV, which then coursed posterior to the pancreas and duodenum to ascend to the porta and supply predominantly the left lobe of the liver (referred to as “splenic PV” later). At least two separate anastomoses were also seen between the two PVs within the liver parenchyma. Keeping in mind the complex portal venous reconstruction that might be required during donor hepatectomy and graft implantation, a multidisciplinary board decided against proceeding with transplant and another donor was identified for workup.

Fig. 1 Coronal-oblique maximum intensity projection (MIP) computed tomography (CT) image (A) demonstrating the “mesenteric portal vein” (solid arrow) and “splenic portal vein” (dashed arrow) along with the splenic vein (arrowhead). Axial CT image (B) showing the differential enhancement of the left lobe of the liver supplied by the splenic portal vein (asterisk).

The vitelline veins give rise to the portal venous system during liver development between the 4th and 12th weeks of gestation.[2] The left and right vitelline veins pass through the septum transversum and enter the sinus venosus, running cranially alongside the foregut. As this occurs, the liver buds begin to form within the septum transversum, with the hepatic cords growing between the vitelline circulation. This process divides the vitelline veins into three segments: the proximal section becomes the hepatic vein, the intermediate section remains as the liver's sinusoids, and the distal section ultimately forms the PV ([Fig. 2]).

Fig. 2 Schematic diagram of the crucial steps in the development of normal portal vein (I, IIA, IIIA) and the likely deviations in our case (IIB, IIIB).

Subsequently, the distal portions of the right and left vitelline veins form three transverse anastomoses around the foregut: the cranial ventral anastomosis, which lies within the liver, and the middle dorsal and caudal ventral anastomoses ([Fig. 2I]). These anastomoses together create a caudal and cranial anastomotic ring around the foregut. Meanwhile, the developing SMV and SV independently join the left vitelline vein below the dorsal anastomosis ([Fig. 2IIA]). The right limb of the caudal ring, the caudal ventral anastomosis, and the left limb of the cranial ring all undergo selective involution ([Fig. 2IIIA]). The PV stem forms from the persistence of a small segment of the left vitelline vein, situated between the middle anastomosis and the entry points of the SMV and SV, the middle dorsal anastomosis, and the right vitelline vein, which lies between the cranial ventral and middle dorsal anastomoses.

In our case, DPV can be attributed to the persistence of the left vitelline vein cranial to the dorsal anastomosis, with the SV joining at the usual point to form the “splenic PV,” while the SMV joins the right vitelline vein to form the “mesenteric PV” ([Fig. 2IIB]). The splenic PV follows the typical postpancreatic, postduodenal course, whereas the mesenteric PV follows the prepancreatic, postduodenal course. The caudal ventral anastomosis is involuted, as evidenced by the absence of the preduodenal PV. The middle dorsal anastomosis remained as the inferior extrahepatic anastomosis, located just below the uncinate process, while the cranial ventral anastomosis persisted as the superior intrahepatic anastomosis connecting the two PVs ([Fig. 2IIIB]). Notably, in the portal venous phase of the CT scan, there was differential enhancement of the two portal systems and the two lobes of hepatic parenchyma, likely due to the faster blood flow in the splenic PV, as suggested by Garnett et al.[3]

To the best of our knowledge, 14 cases of DPV have been reported.[4] Out of these, 11 cases can be classified as true DPV, where both PVs enter the liver through the porta hepatis. In the remaining three cases, one PV entered via the porta hepatis, while the other directly entered the hepatic parenchyma. In most cases, including ours, the splenic PV followed the typical postpancreatic, postduodenal course. However, the mesenteric PV followed either a preduodenal or a prepancreatic, postduodenal course, with our case falling into the latter category.

DPV can be asymptomatic or associated with a range of complications, including abdominal pain, dyspepsia, portal hypertension, and obstructive biliopathy.[4] Three reported cases of DPV observed differential geographical fatty infiltration of the liver parenchyma, where the area spared from fat accumulation primarily received blood flow from the mesenteric PV. Two of these cases developed portal hypertension, one of which resulted in fatal gastrointestinal hemorrhage. The presumed cause in these instances was stenosis of the anastomotic segments connecting the two PVs and their abnormal course. In another case, compression of the common bile duct by the venous fenestration of one of the PVs led to bile duct stenosis and biliary stones.[4]

Even when detected incidentally, as in our case, DPV has significant clinical implications for both the surgeon and the interventional radiologist.[5] Due to the multiple intrahepatic connections between the two PVs, donor hepatectomy involving either lobe could be challenging and may necessitate multiple porto-portal anastomoses between the donor and the graft. For patients undergoing endovascular hepatic procedures, a thorough understanding of the portal venous anatomy is essential for the interventional radiologist to ensure the best possible outcome.

 

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Conflict of Interest

None declared.

• References

• 1 Dighe M, Vaidya S. Duplication of the portal vein—a rare congenital anomaly. Br J Radiol 2009; 82 (974) e32-e34
• 2 Hikspoors JP, Peeters MM, Mekonen HK. et al. The fate of the vitelline and umbilical veins during the development of the human liver. J Anat 2017; 231 (05) 718-735
• 3 Garnett ES, Goddard BA, Markby D, Webber CE. The spleen as an arteriovenous shunt. Lancet 1969; 293 (7591) 386-388
• 4 Yamaoka T. Multiple portal veins in the hepatoduodenal ligament: evidence of “duodenal reverse rotation” hypothesis?. Radiol Case Rep 2023; 18 (12) 4443-4448
• 5 Marks C. Surgical implications of portal venous system malformation. Ann R Coll Surg Engl 1974; 55 (06) 299

Publication History

Article published online:
01 April 2025