A real and rare type of complete portal vein duplication: a case description and literature analysis

Introduction

Duplication of the portal vein (DPV) is an uncommon, yet a real, developmental anomaly of the portal venous system (1). It presents as two separated portal veins (PV) coursing towards porta hepatis and dividing into segmental branch morphologically. A few types of DPV due to different developmental variations of vitelline system and umbilical vein in embryological life have been described in previous reports. Some life-threatening complications in this anomalous condition, such as portal hypertension or gastrointestinal hemorrhage, ought to be cautioned. This report describes a case of DPV manifesting as two completely separated portal systems without any confluence at the porta hepatis and intrahepatic part. PV hypoplasia of segment branches and preduodenal PV were also presented.

Case presentation

A 71-year-old female presented to the digestive system department in our institution with a complaint of a longstanding abdominal distension and dyspepsia. The results of laboratory test were as follow: aspartate aminotransferase, 21.4 U/L; alanine aminotransferase, 13 U/L; total bilirubin, 11.9 µmol/L; creatinine, 78 µmol/L and all tumor markers were normal. The patient was also negative for hepatitis, chronic hepatic diseases and diabetes mellitus, and denied a history of familial genetic disease. She reported that an endoscopic submucosal dissection of stomach was performed 10 months ago and signet-ring cell carcinoma was diagnosed pathologically. All procedures performed in this study were in accordance with the ethical guidelines of the institutional and/or national research committees and with the Declaration of Helsinki (as revised in 2013). Written informed consent was obtained from the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Radiological examinations

A routine contrast-enhanced computed tomography (CT) of the abdomen and pelvis revealed many dilated and tortuous vessels in the portal hepatis area. In addition, the early evident enhancement of dorsal part of abnormal portal vessels extending from the splenic vein in the arterial phase and a preduodenal portal vein was observed (Figures 1,2). The coronal CT in the portal vein phase showed that superior mesenteric vein and splenic vein coursed separately into the liver and no precise confluence between them in the region where the main PV originally coursing. The superior mesenteric vein was found lying anteriorly, inferior, and ventral to the splenic vein. Notably, a “bridge”, about 2.2 cm long, seemed to connect the two portal systems at the lower level of the third part of duodenum. The maximum intensity projection on CT revealed the stenosis at the both distal portion of the “bridge” vein (Figure 3).

Figure 1 The arterial phase CT showed dilated and tortuous vessels in the portal hepatis area indicated by the arrows, with early evident enhancement of dorsal vessels extending from the splenic vein. The edge and shape of hepatic segment V of portal vein are irregular. CT, computed tomography.

Figure 2 A preduodenal portal vein is noted by arrows in the portal vein phase CT showed a preduodenal portal vein. CT, computed tomography.

Figure 3 The maximum intensity projection on coronal CT revealed a complete duplicated portal vein embracing separated splenic vein (thin arrow) and superior mesenteric vein (thick arrow) courses separately without any confluence to form a main trunk and supply the liver without traffic branches. In addition, a little stenosis was presented at the distal portion of the “bridge” vein (circle). CT, computed tomography.

Based on the findings of obvious homogeneous enhancement in the left and right anterior liver lobe as well as probable hypoplasia of the PV of segment IV, V and VIII regarding vessel edge and shape, a diffuse arterioportal fistula beyond CT density resolution was suspected in this case. However, the digital subtraction angiograph demonstrated no abnormal channels between arteries and portal or hepatic veins. The result of hepatic vein pressure gradient was also negative (free hepatic vein pressure 3.4 mmHg, wedge hepatic vein pressure 6.8 mmHg). Considering no evidence of portal hypertension and potential puncture complications, portography was not performed.

Follow-up visits

During the regular follow-up visits in the past one year after discharge, no adverse events such as peptic bleeding occurred. So far, her complained symptoms have been relieved with the administration of necessary drugs (Proton pump inhibitors and gastrointestinal prokinetic agents) in the outpatient department of digestive medicine as appropriate.

Discussion

DPV is a rare anomaly of the portal venous system, with a low incidence rate. During embryonic development, both the vitelline and umbilical venous systems play crucial roles. In normal development, hepatic bud cells invade the vitelline vein cranially, forming an eight-shaped anastomosis, which gradually disappears, eventually forming the normal portal venous system (2).

Interestingly, in this case, all above-mentioned normal portal embryonic developments did not occur, and the dorsal anastomosis should not have atrophied (Figure 4). Notably, it is the ventral and caudal anastomosis that will develop as the preduodenal portal vein.

Figure 4 Embryonic development of the portal system. (A) A figure-of-eight cross anastomoses rotating round the foregut develops between two vitelline veins; (B) the left limb of the cranial ring, the right limb of the caudal ring and the ventral-caudal anastomosis progressively obliterate (note dashed line). On the basis of the normal development, an S-shaped portal vein is formed. And there is a joint between the bilateral umbilical veins to the vitelline venous system; (C) in this case, dorsal anastomosis atrophied (dashed line) and other anastomoses still existed; (D) the final portal system morphology of this patient (the yellow solid line denoting the gastrointestinal tract).

Currently, no literature or case reports have described a complete DPV which courses separately without any confluence to form a main trunk and supply the liver without traffic branches. However, two types of DPV were reported: complete DPV (3-6), and a normal portal vein accompanied by accessory PV (7-10). In this case, a complete DPV was described, where the DPV ran separately without forming a main trunk. Additionally, there was a “bridge” vein connecting two PV and stenosis located in distal potion of residual ventral anastomosis, transient inhomogeneous perfusion and hypoplasia of segmental PV were observed.

Although the abnormal structure of DPV may lead to some clinical symptoms such as liver periphery or intrahepatic tumor-like structure, impaired liver function and the occurrence of fatty liver or right upper quadrant pain (3,8,10). Additionally, it may lead to severe complications such as esophageal variceal bleeding due to portal hypertension, resulting in fatalities as reported (6). Actually, the stenosis at the points of junction of the primitive portal system branches is responsible for it. Similarly, in this case, CT revealed that two slits situated in the both distal portion of the “bridge” vein. However, only dyspepsia was found in this patient. Given that no clinically significant hemodynamics changes were induced by portal vein duplication, there was no determined evidence on the association between patient’s vascular abnormalities and her complaints. It was possible that her potential concomitant gastrointestinal disease, whatever organic changes or digestive dysfunction, is responsible for related symptoms.

For patients with only mild abdominal symptoms, a modified healthy lifestyle and medicine administration are preferred. However, for individuals with severe portal hypertension or secondary complications, like hemorrhage, interventional treatments like balloon dilation or stent placement for stenotic areas, or surgical procedures such as shunt or devascularization surgeries, are warranted.

Conclusions

In summary, we encountered a patient with a complete DPV which coursed separately without any confluence to form a main trunk. A stenosis situated in the junction of portal system and residual anastomosis was observed. Fortunately, no severe complications occurred. However, the underlying regional portal hypertension and secondary variceal hemorrhage resulting from the potential stenosis should be noted, despite with a quite low incidence. The treatment protocol, medication, interventional procedures, or surgery, depends on the symptom severity. Understanding the fundamental developmental details of portal vein embryogenesis is essential to manage such patients properly.

Acknowledgments

Funding: None.

Footnote

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-24-454/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical guidelines of the institutional and/or national research committees and with the Declaration of Helsinki (as revised in 2013). Written informed consent was obtained from the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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