Anatomic Variations of the Right Portal Vein: Prevalence, Imaging Features, and Implications for Successful Transjugular Intrahepatic Portosystemic Shunt Creation

Classification of variant portal vein anatomy based on three-dimensional CT: surgical implications

PURPOSES

The purpose of this study was to develop a new and more comprehensive classification system for portal vein (PV) variations using three-dimensional visualization and evaluation (3DVE) and to discuss the prevalence rates and clinical implications of the variants.

METHODS

The anatomies of PVs were tracked and analyzed by using three-dimensional visualization of CT images acquired between 2013 and 2022. Scans from 200 adults were evaluated and a total of 178 patients (N = 178) were included in the study. The new classification system, named BLB classification, was developed based on the level of the absent PV branch in each variant anatomy.

RESULTS

Using the BLB classification system, PVs were divided into thirteen subtypes. Only 82.6-84.8% of the portal veins of the 178 patients were depicted in Atri's, Cheng's or Covey's classification, compared with 100% identified by the BLB classification. The BLB classification was validated against external data sets from previous studies, with 97.0-98.9% of patients classified by the BLB system.

CONCLUSION

Variant PV anatomies are more commonly seen based on 3DVE than in previous reports. The BLB classification covers almost all portal vein variants and may be used for planning liver surgery.

Hepatic portal vein branching patterns according to different liver assessment methods and classifications of branching type

BACKGROUND

It is known that there are varying frequencies of hepatic portal vein branching patterns found in the literature. Studies use different methods and classifications to evaluate the anatomy of the portal vein, which limits accurate comparison between studies and the determination of true frequency of branching patterns in different populations. The aim of the present study was to investigate the intrahepatic branching of the portal vein in corrosive samples using different methods - somatoscopic and computed tomography (CT) and compare with similar studies as well as compare the reclassified data according to the most popular classifications used in the literature.

METHODS

A total of 105 liver corrosion specimens from the 1960-1980 period (51 male and 54 female individuals; min-max age variation - 21-90 y., M=59,46 y.) were investigated. The branching patterns of the hepatic portal vein (HPV), left (HPV-LB) and right branch of hepatic portal vein (HPV-RB), and their segmental branches were examined and scanned by CT. Standard HPV ramification was considered, when HPV divided into HPV-LB and HPV-RB, HPV-RB bifurcated to the anterior and posterior branches, and further segmental ramification into the superior and inferior branches was considered standard. We compared the HPV main branch length and diameter measurements between manual and CT method. A review of the literature was performed on portal vein branching variations.

RESULTS

The standard HPV ramification pattern was detected in 85.7% of the cases in both somatoscopic and CT evaluation. Variations related to the main branches were HPV trifurcation - 7.6%, posterior branch of right branch of hepatic portal vein from HPV - 4.8% and 5.7%, HPV quadrifurcation 1.9% and 1% respectively, in somatoscopic and CT evaluation. There was a significant difference between HPV-LB length and diameter in CT and manual measurements. According to the literature, more variations are seen using the CT method versus somatoscopic corrosion cast evaluation. The varying frequency in studies may be explained by a lack of one unanimous classification of branching patterns (some authors do not consider segmental variations as standard HPV ramification) and different evaluation methods.

CONCLUSION

Somatoscopic evaluation of the branching patterns of the hepatic portal vein in corroded specimens and their CT reconstructions did not differ significantly (which allows relatively accurate comparison of old specimens with newer data). However, the ability to evaluate the reconstructed 3D images of the specimens allowed a more accurate assessment of segmental branching and measurements of lengths and diameters. Standard HPV branching (according to a self-developed classification) in this study was 85.7%. Depending on the classification, the rate of standard branching in the same corrosive samples varied from 63.8% to 84.8% of all cases, indicating that the lack of a unified and stable classification makes it difficult to compare the results of different studies. Deviations from standard branching are very important in surgical procedures and liver transplantation.

A systematic review and meta-analysis of portal vein morphometry in pediatric and adult populations: Drawing the line between normal and abnormal findings

PURPOSE

The morphometry of the hepatic portal vein is of clinical importance, particularly in pre-operative assessments, surgical management, and diagnoses of liver conditions. This systematic review and meta-analysis aimed to characterize the morphometry of the normal portal vein in both pediatric and adult patients.

METHODS

The study, conducted using the PRISMA guidelines and registered with PROSPERO, utilized the MEDLINE, EMBASE, SCOPUS and Web of Science databases up to May 2020, and updated to May 2023. All studies reporting extractable data on diameter, length, and cross-sectional area (CSA) of the main, left, and right portal veins (PV, LPV, RPV, respectively) were included. The AQUA Tool was used to assess the quality of the included studies. Data analysis included subgroup analyses based on geographical location, sex, age, and imaging modality.

RESULTS

A total of 122 studies with 11,637 subjects were eligible for inclusion. Overall, the pooled mean diameter of the PV (PVD) was 10.09 mm (95% CI: 9.56-10.62). Significant differences in diameter were found between pediatric (6.60 mm; 95% CI: 5.38-7.82) and adult (10.72 mm; 95% CI: 10.25-11.19) subjects. Additionally, there was a significantly larger PVD measurement from computed tomography (CT) than other imaging modalities: CT, 13.28 mm (95% CI: 11.71-14.84); magnetic resonance imaging (MRI), 10.50 mm (95% CI: 9.35-11.66) and ultrasound (US), 9.81 mm (95% CI: 9.47-10.16). The mean diameters of the LPV and RPV were 8.27 mm (95% CI: 6.78-9.77) and 8.33 mm (95% CI: 6.70-9.95), respectively. Mean PV length in adults is 48.63 mm (95% CI: 35.63-61.64). Mean CSA of the PV was 1.09 cm2.

CONCLUSIONS

The study obtained aim to improve the understanding of portal vein anatomy, especially with relevance to surgical interventions of the liver in both pediatric and adult patients. Measurements from ultrasound imaging closely approximates the generated pooled PVD mean for pediatric and adult patients. CT imaging, however, significantly exceeded the established 13 mm threshold for adults. For pediatric patients, a threshold of 8 mm is proposed as a diagnostic upper limit for a normal PVD. Although not significant, the PVD decreased from the portal confluence towards its bifurcation.

Portal Vein Variations, Clinical Correlation, and Embryological Explanation: A Review Article

Portal vein (PV) is a large vein that collects blood from the abdominal part of gall bladder, pancreas, alimentary tract, and spleen and transports to the liver. One of the parts of the extraembryonic venous system, the vitelline veins, is where PV starts. In about five weeks of gestation, a venous plexus is formed, and variations in this plexus lead to portal variance. The junction of superior mesenteric and splenic veins is typically where the vein begins to network. There are five types of branching patterns of the right PV: conventional branching, trifurcation branching, early branching, separate segment 7 branching, and separate segment 6 branching. To perform pancreatic, duodenal, and liver surgeries, knowledge of variations in PV formation is important. For surgical and interventional operations to be accurate, it is crucial to understand the architecture of the PV and its anomalies. As distinct regions of the brain connect with one another, portal architecture is frequently observed in imaging investigations. Portal hypertension is characterized as an increase in blood pressure in the portal venous system (PVS) in the context of severe liver disease, such as cirrhosis. Non-invasive methods for examining the anatomy and anomalies of the PV include ultrasound, computed tomography (CT), and magnetic resonance (MR). There are many abnormalities of PVS that have been discussed in the articles such as Congenital PV Absence; PV Branches Congenitally Grow in Structure; Hypoplasia, Atresia, and Stenosis of the PV; and Portosystemic Shunts.

Duplicated inferior vena cava-trifurcated portal vein: a rare anatomical variation encountered during Whipple procedure

The inferior vena cava (IVC) is the largest single vein in humans. However, during embryogenesis, abnormalities can occur resulting in a duplicated IVC. The portal vein (PV) offers the main blood flood to the liver, forming by the left and right PV. A number of anatomical variations are noticed, underlying the great importance of the pre-operative imaging workup. This case report presents a duplicated IVC and a trifucated PV that were incidentally found in an 82 year-old Caucasian male with pancreatic ductal adenocarcinoma who underwent pancreatoduodenectomy (Whipple procedure). Although some anatomical variations, including the duplication of the IVC and the trifurcation of PV, may be rare to the general population, the suspicion of their existence should always be taken under consideration from surgeons during hepatobiliary or retroperitoneal operations.

Clinical Importance of Main Portal Vein and Right Portal Vein Variations: A Prevalence Study With 128-Slice Multidetector Computed Tomography

OBJECTIVES

The portal vein variation type significantly affects the outcome of transplant surgery, hepatectomies, and interventional radiological procedures. To reveal variation types, especially rare types, we used high-technology multidetector computed tomography.

MATERIALS AND METHODS

We evaluated multiphase abdominal multidetector computed tomography scans of 278 consecutive patients. Multidetector computed tomography scans were processed for axial, coronal, and axial-oblique multiplane reformation and for maximum intensity projection. Variations of the main portal vein and right portal vein were simulta-neously analyzed by 2 radiologists. Prevalence of each variation and differences in sexes were investigated.

RESULTS

Variant anatomy was detected in 29.5% of main portal veins and 20.9% of right portal veins. There was no statistical difference between sexes. Type 3 was reported as the most frequent variant of main portal vein, whereas type 4 was the most frequent variant of right portal vein. Some miscellaneous types were also ascertained.

CONCLUSIONS

Different types of anatomic variations may adversely affect the course of surgery and interventional radiological procedures. Fortunately, radiologists can now discover the critical types by using the new generation multidetector computed tomography with 3-dimensional reconstruction techniques. This information should be included in the radiology reports of patients who are scheduled for major surgery.

Role of CT Imaging With Three-Dimensional Maximum Intensity Projection Reconstruction in the Evaluation of Portal Vein Variants at a Tertiary Care Hospital

INTRODUCTION

Portal vein (PV) is the principal blood vessel transporting blood from the alimentary tract and spleen to the liver. The aim of this study is to determine the prevalence of PV anatomical variations in our population using multidetector CT with maximum intensity projection (MIP) technique at a tertiary care hospital.

METHODS

This cross-sectional study was prospectively conducted from November 2018 to June 2019 in the Department of Radiology at a tertiary care hospital in Karachi. After informed consent, all the patients with no known hepatic pathology undergoing routine abdomen CT were included in this study. Patients with previous hepatic resection surgeries, undiagnosed large hepatic tumors/metastasis, and those with PV thrombosis were excluded.

RESULTS

A total of 500 patients (256 males and 244 females) were included in the study; the mean age of female patients was relatively higher as compared to the male patients (53.80 ± 18.44 vs. 44.15 ± 19.94 years; p = 0.000). Standard PV anatomy (type 1) was found in 438 patients (87.6%). Trifurcation (type 2) occurred in 18 patients (3.6%). Right posterior portal vein as the first branch of main PV (type 3) was found in 22 patients (4.4%). A separate branch of the right portal vein (RPV) to segment VII (type 4) and separate branch of the RPV to segment VI (type 5) were found in 6 (1.2%) and 16 (3.2%) patients, respectively.

CONCLUSION

Our study displayed a relatively higher frequency of standard PV anatomy (type 1) compared to previous studies. We highlight the role of MIP in the analysis of hepatic venous anatomy with its utility demonstrating improved detection of variations.