Abstract
An in-depth understanding of portal venous anatomy, particularly its variants, is essential for interventional radiologists performing complex hepatobiliary procedures such as transjugular intrahepatic portosystemic shunt (TIPS) creation. Anatomical variations in the portal venous system occur in approximately 35% of the population, and failure to identify these variants can result in significant procedural complications including vascular injury and postprocedural liver failure. This article discusses the most common (types I–V) portal vein variants and the importance of their preprocedural identification, their potential impact on procedural outcomes, and the role of advanced imaging techniques in mitigating risks associated with these anatomical variations.
Keywords: portal vein, portal vein anatomy, mesenteric vein, interventional radiology
Interventional radiology (IR) has emerged as a cornerstone in the management of hepatobiliary disorders, offering minimally invasive alternatives to surgical interventions. Procedures such as transjugular intrahepatic portosystemic shunts (TIPS) are routinely performed to manage portal hypertension and its sequelae. However, procedural success hinges on a comprehensive understanding of the portal venous anatomy and its variations. An estimated 35% of individuals present with variant portal vein anatomy, which can complicate the technical execution of any IR procedure that requires portal venous access, such as TIPS. Misidentifying or failing to recognize these variants can lead to significant complications, including vascular damage and liver failure. This article will provide an in-depth review of the clinical relevance of portal vein anatomy variants in IR, emphasizing the importance of preprocedural imaging, the implications of variant anatomy on procedural outcomes, and strategies for managing these variations.
Pathophysiological Basis for Transjugular Intrahepatic Portosystemic Shunt
Portal hypertension in liver disease arises mainly due to increased intrahepatic vascular resistance and abnormal systemic and splanchnic circulation dynamics. In cirrhosis, structural changes like fibrosis and increased hepatic vascular tone elevate resistance within the liver's microcirculation. This is exacerbated by the impaired function of liver sinusoidal endothelial cells (LSECs) and the activation of hepatic stellate cells (HSCs). LSECs demonstrate reduced nitric oxide (NO) production, which in turn contributes to vasoconstriction, while activated HSCs adopt a contractile phenotype, enhancing intrahepatic resistance. 1
The pathophysiology extends to the development of collateral vessels, primarily due to the increased portal pressure, and splanchnic vasodilation, which amplifies blood flow to the portal vein. This vasodilation, driven by excess NO and other vasodilators, supports the hyperdynamic circulatory syndrome—characterized by increased cardiac output, decreased systemic vascular resistance, and lower mean arterial pressure. 1
Key mechanisms contributing to this pathology include endothelial dysfunction, increased vasoconstrictive signaling (e.g., endothelin-1, thromboxane A2), and angiogenesis. These factors together establish a vicious cycle that perpetuates high portal pressure, leading to complications like varices and ascites. Effective treatment of portal hypertension focuses on reducing intrahepatic resistance and modulating splanchnic blood flow to relieve portal pressure. 1 Indications and contraindications for TIPS creation are summarized in Tables 1 and 2 .
Table 1. Indications for transjugular intrahepatic portosystemic shunt.
| Indications |
|---|
| Refractory ascites |
| Variceal bleeding refractory to therapy |
| Budd–Chiari syndrome |
| Hepatic hydrothorax resistant to diuretics |
| Portal hypertensive gastropathy |
| Prevention of rebleeding from varices |
Table 2. Contraindications for TIPS.
| Relative contraindications | Absolute contraindications |
|---|---|
| Severe hepatic encephalopathy (HE) | Uncontrolled systemic infection |
| Severe right-sided heart failure or pulmonary hypertension | Severe right-sided heart failure or pulmonary hypertension (pulmonary artery pressure >45 mm Hg) |
| Moderate hepatic dysfunction (Child–Pugh C, MELD > 18) | Severe liver dysfunction without transplant potential |
| Polycystic liver disease | Hepatic malignancy with vascular invasion |
| Active sepsis or systemic infection | Uncorrected coagulopathy (INR > 5.0, platelet count < 20,000/mm 3 ) |
| Moderate renal impairment | Severe thrombocytopenia or high risk of bleeding |
| Previous TIPS dysfunction with technical issues | Unrelieved biliary obstruction |
| Advanced age or frailty | Uncontrolled heart failure |
Abbreviations: INR, international normalized ratio; TIPS, transjugular intrahepatic portosystemic shunt.
Notes: Child – Pugh: Categorizes liver function in classes A, B, and C based on clinical and laboratory parameters. Model for End-Stage Liver Disease (MELD): Uses objective laboratory values to estimate mortality, and is a good predictor of post-TIPS mortality. 12 13 See Appendices I and II .
Appendix I. Child–Pugh.
| Parameter | 1 point | 2 points | 3 points | Description |
|---|---|---|---|---|
| Serum bilirubin (mg/dL) | <2 | 2–3 | >3 | Indicates liver's ability to excrete bilirubin; elevated levels suggest impaired liver function |
| Serum albumin (g/dL) | >3.5 | 2.8–3.5 | <2.8 | Reflects liver's synthetic function; low levels indicate reduced liver protein production |
| INR (prothrombin time) | <1.7 | 1.7–2.3 | >2.3 | Measures blood clotting ability; prolonged INR indicates impaired coagulation due to liver disease |
| Ascites | None | Mild (controlled with diuretics) | Moderate to severe (refractory to diuretics) | Indicates portal hypertension severity; accumulation of fluid in the abdomen is a hallmark of decompensation |
| Hepatic encephalopathy | None | Grades I–II (mild to moderate) | Grades III–IV (severe) | Evaluates cognitive dysfunction due to liver's inability to detoxify ammonia and other neurotoxins |
Notes: Child – Pugh score classification 12 : Sum the points for each parameter (range: 5–15).
Classification:
Class A (5–6 points): Well-compensated disease.
Class B (7–9 points): Significant functional compromise.
Class C (10–15 points): Decompensated liver disease with poor prognosis.
Appendix II. Model for End-Stage Liver Disease (MELD) score 13 .
| Parameter | Description | Role in MELD calculation |
|---|---|---|
| Serum bilirubin | Reflects liver's ability to excrete bilirubin; elevated levels indicate impaired liver function | Higher values increase the score, reflecting worsening liver dysfunction |
| INR (prothrombin time) | Measures blood clotting; elevated INR indicates impaired liver synthesis of clotting factors | Prolonged INR significantly increases the score, indicating coagulopathy due to liver failure |
| Serum creatinine | Indicates renal function; higher levels suggest hepatorenal syndrome or impaired kidney function | Elevated creatinine increases the score, highlighting renal involvement in liver disease |
| Sodium (optional in MELD-Na) | Accounts for hyponatremia, a common complication of advanced liver disease (MELD-Na version) | Severe hyponatremia (<125 mmol/L) increases mortality risk, influencing the MELD-Na score |
| MELD score range | 3-month mortality risk | Clinical Implications |
| <9 | <2% | Indicates well-compensated liver function; low risk of mortality |
| 10–19 | 6–20% | Moderate liver dysfunction; may require closer monitoring and interventions |
| 20–29 | 20–50% | Advanced liver disease; higher urgency for transplantation |
| 30–39 | 50–80% | Severe liver dysfunction; high priority for liver transplant |
| ≥40 | >80% | Extremely poor prognosis without immediate intervention or transplantation |
Abbreviation: INR, international normalized ratio.
Transjugular Intrahepatic Portosystemic Shunt Techniques
Conventional TIPS Technique
The TIPS procedure, typically performed under general anesthesia to ensure patient comfort and precise procedural control, begins with the administration of prophylactic antibiotics to minimize infection risk. Access to the central venous system is achieved via the right internal jugular vein, which is the preferred route. An angled catheter is advanced into the right hepatic vein, which serves as the entry point for the subsequent steps. To visualize the portal venous system and identify a fluoroscopic target for portal vein access, a balloon occlusion venogram using CO 2 is performed.
Using a specialized TIPS needle included in commercially available kits, the right portal vein is accessed from the right hepatic vein under fluoroscopic and ultrasound guidance. Real-time ultrasound enhances visualization of the needle's trajectory, increasing the accuracy of portal vein entry. Proper positioning within the portal vein is confirmed through blood aspiration followed by contrast injection, with the ideal puncture site located 1 to 2 cm from the main portal vein (MPV) bifurcation to avoid complications such as hemoperitoneum. If direct portal vein access proves difficult, a percutaneous transhepatic guidewire can be placed into the portal vein, serving as a fluoroscopic target.
Once portal vein access is confirmed, an angiographic catheter is advanced to perform a venogram, ensuring the suitability of the chosen entry point. Pressure measurements are obtained from the portal vein and the right atrium to calculate the initial portal-to-systemic gradient, which guides therapeutic decisions. In cases where a competing splenorenal shunt is present, embolization of the shunt may be necessary to optimize the gradient and improve hemodynamic outcomes.
The created tract between the hepatic and portal veins is then dilated to a diameter of 8 to 10 mm. A partially covered stent is deployed, with the uncovered portion positioned in the portal vein and the covered segment extending to the junction of the hepatic vein and the inferior vena cava (IVC). Careful stent placement is crucial to avoid extending it too far into the IVC or deeply into the portal vein, as improper positioning can complicate future liver transplantation or affect the functionality of the shunt. Persistent varices observed post-TIPS placement are treated with embolization using coils or plugs, or sclerosis, to prevent ongoing or recurrent variceal bleeding.
Following stent placement, the final portal-to-systemic gradient is measured and documented to serve as a baseline for future interventions (see Fig. 1 ). The patient is closely monitored postprocedure, with particular attention to liver enzyme levels to detect potential hepatic dysfunction. Within 48 to 72 hours, a baseline Doppler ultrasound is performed to assess shunt patency. Earlier imaging is avoided due to potential artifacts caused by air bubbles within the polytetrafluoroethylene (PTFE) material of the stent, which can simulate flow abnormalities.
Fig. 1.
General TIPS schematic.
Long-term surveillance involves periodic Doppler ultrasound studies to identify shunt dysfunction, indicated by velocities exceeding 190 cm/s or dropping below 90 cm/s, or a significant change of more than 50 cm/s from baseline. If these abnormalities are detected, further evaluation with a TIPS venogram and direct pressure measurements in the angiography suite is pursued. Shunt dysfunction due to intimal hyperplasia can be managed with balloon dilation or restenting to restore adequate flow and maintain shunt function. This structured and systematic approach ensures optimal outcomes for patients requiring TIPS. General immediate and long-term complications associated with TIPS creation are summarized in Table 3 .
Table 3. General complications associated with TIPS creation, independent of individual technique.
| Immediate Complications |
| Puncture-related bleeds (e.g., hemoperitoneum) |
| Stent malposition or migration |
| Early shunt thrombosis (technical issues or bile duct injury) |
| Shunt-related encephalopathy (30–46%) |
| Hepatic function deterioration |
| Shunt stenosis |
| Long-term complications |
| Intimal hyperplasia within the TIPS |
| Complete TIPS thrombosis |
| Recurrence of portal hypertension (from intimal hyperplasia or thrombosis) |
Abbreviation: TIPS, transjugular intrahepatic portosystemic shunt.
Intravascular Ultrasound Guidance/Intracardiac Echocardiography Technique
Each of the TIPS approaches presents an advantage depending on patients' anatomy and medical conditions. Intravenous ultrasound (IVUS) is advantageous in the settings of portal vein thrombosis, small or variant portal anatomy, Budd–Chiari syndrome, or liver masses. IVUS offers real-time cross-sectional understanding of the spatial relationship between the hepatic and portal vein, which many other modalities cannot do (wedged CO 2 portal venography). This promotes procedural success with less passes. It also allows for decreased fluoroscopy times, contrast agent volume, and overall procedure time. 2
Once IVUS approach is selected due to the factors mentioned earlier, the preprocedural preparation occurs in a typical TIPS fashion. The IVUS probe can be inserted in tandem with the access used for TIPS placement, or via one of the common femoral veins. This method benefits from having an assistant operator, who can pin the IVUS while the primary operator attempts access. An 8-Fr IVUS probe is advanced through a 9-Fr sheath directly into the IVC. Once placed in the retrohepatic IVC, and the hepatic vein confluence is visualized, orientation is achieved by rotating the probe until the aorta is identified. Moving the probe caudally allows visualization of the portal veins, and color Doppler can be used to identify the different vessels. 2 It is critical not to underestimate the angle of the needle approach due to unintentional probe angulation. Once all vessels are identified, and the optimal angle chosen, the hepatic vein can be cannulated. The IVUS probe can then be rotated until the selected portal vein is seen in the same plane as the cannulated hepatic vein, and the needle can be advanced through the liver parenchyma into the targeted portal vein (see Fig. 2 ).
Fig. 2.
ICE/IVUS-guided TIPS.
Intravascular access can be confirmed via aspiration. If aspiration cannot be performed due to a thrombus or an occluded needle, saline injection or wire placement can confirm the location of the needle tip. Once portal vein access is obtained, the usual TIPS technique can resume thereafter. IVUS is also an excellent option for parenchymal tract length measurement, which is an essential step in TIPS placement.
IVUS-guided TIPS creation offers precise real-time visualization of the hepatic vasculature and portal venous system, but it also presents unique challenges, summarized in Table 4 .
Table 4. Specific challenges associated with IVUS-guided TIPS creation.
| Technical Challenges |
| Learning curve |
| IVUS requires specific training and experience for effective use and accurate interpretation |
| Operators unfamiliar with IVUS imaging may struggle with real-time decision-making |
| Vascular tortuosity |
| In patients with altered hepatic or venous anatomy, navigating the IVUS catheter to optimal positions for imaging and guidance can be challenging |
| Patient-specific challenges |
| Severe portal hypertension |
| High portal pressures can lead to excessive turbulence, making IVUS imaging interpretation more complex |
| Advanced liver disease |
| Severe fibrosis or cirrhosis may distort hepatic and portal vein anatomy, complicating vessel visualization and puncture |
| Obesity |
| In obese patients, catheter manipulation and imaging quality may be compromised due to challenges in accessing and visualizing deep structures |
| Risk of complications |
| Prolonged procedure time |
| Use of IVUS can increase procedure duration, potentially elevating the risk of complications such as bleeding or thrombosis |
| Limited hands-on evidence |
| While IVUS is recognized as valuable, its routine adoption may be limited due to a lack of large-scale comparative studies confirming its superiority in standard TIPS creation |
Despite these challenges, the integration of IVUS into TIPS procedures is expected to become more seamless and widely adopted.
Transsplenic/Transportal Technique
The transsplenic approach for TIPS creation is a technically demanding but viable option for patients with challenging portal venous anatomy. This procedure is reserved for cases where the portal vein is occluded or inaccessible via transjugular or transhepatic routes, or when anatomy precludes standard TIPS creation, such as severe liver atrophy or distorted venous anatomy. 3 Careful patient selection is essential, including preprocedural assessment of bleeding risk and platelet count. Detailed imaging with CT or MRI is crucial to evaluate splenic size and location, portal vein anatomy, and the presence of thrombus or collaterals.
After careful preprocedural planning, color Doppler US and grayscale can be used to assess the spleen. Ultrasound guidance is used to gain percutaneous access to the splenic vein from a lateral intercostal or subcostal approach, typically aiming for a central intraparenchymal perihilar branch of the splenic vein. 3 Some institutions require first establishing transjugular access and advancing into the hepatic vein via the IVC. In this procedure, wedged venography can be used to assess the patency of intrahepatic portal branches. 4 When percutaneous splenic access is obtained, guidewire and catheter can then be advanced from the splenic vein to the portal vein (see Fig. 3 ). Portal venography can be used to assess for accidental arterial puncture. As opposed to the single-pass technique utilized in conventional TIPS, in the transsplenic approach, the needle is incrementally advanced toward the snare. Though TIPS is traditionally transhepatic, recent data have emerged demonstrating that the transsplenic approach may be technically easier, and in one case series, the success rate was 100%. 4 Despite these promising results, there are several well-documented technical challenges associated with this approach, which are summarized in Table 5 .
Fig. 3.
Transsplenic TIPS.
Table 5. Specific challenges associated with transsplenic TIPS creation.
| Technical challenges |
| Splenic access |
| Percutaneous splenic access can be technically difficult in patients with small or inaccessible spleens due to prior surgery, injury, atrophy, or anatomic variability |
| Bleeding risk |
| Splenic puncture has an inherently high risk of hemorrhage due to the spleen's vascularity and portal hypertension. Underlying coagulopathy further exacerbates this risk |
| Portal vein targeting |
| Navigating from the splenic vein to a suitable portal vein branch for TIPS creation can be challenging, especially in the presence of portal vein thrombosis and/or aberrant or distorted venous anatomy |
| Increased procedural complexity |
| Requires expertise in challenging wire and catheter manipulation, and advanced imaging such as IVUS is often required to aid guidance |
| Risk of complications |
| Radiation exposure |
| Transsplenic shunt creation can increase procedure duration elevating the risk of complications such as bleeding as well as increasing radiation exposure for both the patient and the operator |
| Postprocedural risks |
| Increased risk of splenic vein thrombosis, splenic infarction, and portal/systemic embolization |
Abbreviations: IVUS, intravascular ultrasound; TIPS, transjugular intrahepatic portosystemic shunt.
Hemostasis management strategies, such as prophylactic embolization of the splenic tract and administration of platelets or coagulation factors, help minimize bleeding risks, and close postprocedural monitoring is critical to identify signs of bleeding or hematoma formation. Postprocedural anticoagulation may be necessary to prevent splenic vein thrombosis or shunt occlusion, with careful balance against bleeding risks.
This procedure is best performed in high-volume centers by experienced interventional radiologists equipped with advanced imaging modalities and surgical backup. If the transsplenic route poses an excessive risk, alternative approaches like percutaneous transhepatic portal vein access or direct intrahepatic portosystemic shunt (DIPS) should be considered.
Gun-Sight Technique
The Gun-Sight procedure is an advanced alternative technique that may be advantageous in the setting of challenging anatomy. This approach is typically considered only in cases with severe stenosis, angulation, portal vein thrombosis, or occlusion of the hepatic veins which would make conventional TIPS impossible.
The process begins with transhepatic access, where a needle is inserted into a branch of the right portal vein, ∼2 to 3 cm peripheral to the portal bifurcation. A safety guidewire is placed within the superior mesenteric vein to maintain stable portal access. A 10-mm nitinol snare is then threaded alongside the guidewire into the portal vein, with the sheath retracted slightly to position the snare in the hepatic parenchyma.
Through a transjugular approach, a larger 25-mm snare is introduced and positioned in the retrohepatic IVC. The imaging intensifier is adjusted to align the portal and caval snares in a near-lateral projection, creating the characteristic “gun-sight” overlap view (see Fig. 4 ). A sheathed needle is advanced through a new transhepatic puncture site, passing precisely through both snares. The needle's position is confirmed with contrast injection into the IVC, and a guidewire is threaded through the sheath and into the IVC. This guidewire is captured with the caval snare and exteriorized through the transjugular route.
Fig. 4.
Gun-sight TIPS.
Next, a larger needle is advanced over the guidewire to establish a direct connection between the portal vein and the IVC. The shunt tract is dilated using an angioplasty balloon to prepare for stent placement. Overlapping Wallstent prostheses are deployed within the shunt tract, and further dilation is performed as needed to achieve the desired portal pressure reduction. The transhepatic sheath is then carefully withdrawn, and the tract is embolized with Gelfoam to prevent intraperitoneal bleeding. Final imaging ensures proper stent positioning and confirms adequate decompression of the portal system, while Doppler ultrasonography can assess shunt flow. This approach promotes a single needle pass and bypasses the hepatic veins entirely, making it particularly advantageous in cases with severe hepatic vein pathology thus reducing the risk of complications. 5 Technical consideration and associated complications are summarized in Table 6 .
Table 6. Specific challenges associated with the gun-sight technique.
| Technical challenges |
| Access challenges |
| Accurate transhepatic access to the portal vein is critical; errors can destabilize portal access or cause improper positioning of snares. Misalignment of portal and caval snares complicates the “gun-sight” overlap view, increasing procedural difficulty |
| Portal vein variants |
| Accessory portal veins or early bifurcations may lead to misplaced shunt or improper decompression of the portal system |
| Risk of complications |
| Radiation risks |
| Multiple punctures and prolonged fluoroscopy times increase radiation exposure; using the left internal jugular vein minimizes this risk |
| Bleeding risks |
| Improper embolization of the transhepatic tract can cause intraperitoneal bleeding |
| Hepatic encephalopathy |
| Targeting nonpreferred veins (e.g., right portal vein) increases the risk of hepatic encephalopathy |
| Technical failures |
| Complex anatomy or poor planning may require multiple attempts, raising risks of trauma or complications |
Procedural Considerations for Transjugular Intrahepatic Portosystemic Shunt
Selecting the vessel that is best suited for a TIPS can be a challenging task when considering the patient's unique anatomy and variants in portal vein anatomy can complicate this step. For instance, an accessory portal vein running parallel to the MPV may be inadvertently punctured, leading to inadequate decompression of the portal system or shunt misplacement. 6 In addition, variants such as early bifurcations can alter the expected flow dynamics post-TIPS, leading to persistent portal hypertension or failure to control symptoms such as variceal bleeding.
Not surprisingly, accurate preprocedural imaging is essential for identifying portal vein variants and planning safe, effective interventions. Contrast-enhanced computed tomography (CT), magnetic resonance imaging (MRI), and Doppler ultrasound provide detailed visualization of the portal venous system, allowing interventional radiologists to map out variant anatomy before performing procedures. 7 CT portography is particularly useful for delineating portal vein anatomy in complex cases, providing high-resolution images of the hepatic vasculature, and identifying any variations that may affect procedural planning.
In addition to two-dimensional imaging, three-dimensional reconstructions from CT angiography can enhance understanding of complex anatomy, thus allowing for precise targeting. These advanced imaging techniques are a critical initial step in mapping out the chosen puncture path and ensuring that variant anatomy is appropriately addressed, reducing the risk of procedural complications and improving patient outcomes. 8
The primary access vessel has historically been the right internal jugular, as it offers a more direct path with less angulation for guide wires and catheters. Interestingly, a study in 2022 found that access through the left internal jugular vein was associated with fewer needle punctures, shorter fluoroscopy times, and lower radiation dose when compared with the right internal jugular vein. 9 In addition, targeting the right portal vein is generally preferred over the left portal vein for access, as it is considered easier and provides a larger target area due to the larger size of the right hepatic lobe. However, at least one study demonstrated reduced risk of hepatic encephalopathy with targeting of the left portal vein, an important clinical consideration. 10
Portal Venous Anatomy: Variants and Procedural Implications
The technical success and challenges of transjugular intrahepatic portosystemic shunt (TIPS) creation are heavily influenced by variations in portal venous anatomy, necessitating tailored procedural strategies and imaging techniques. Portal vein variants can significantly impact access to target vessels and the complexity of achieving a functional shunt, with success rates varying by anatomy type. 11 12 These are summarized in Table 7 .
Table 7. Portal vein variant anatomy and their specific individual procedural challenges.
| Type of portal variant anatomy | Key challenges |
|---|---|
| Type I, conventional anatomy | Predictable, with minimal challenges |
| Type II, trifurcation | Complex branch selection; risk of puncturing small vessels or bile ducts |
| Type III, right posterior segmental branch | Needle alignment with posterior branch; risk of nontarget puncture |
| Type IV, segment VII as the first branch off the right portal vein | Large caliber target in predictable location, minimal challenges |
| Type V, segment VI as the first branch off the right portal vein | Large caliber target in predictable location, minimal challenges |
Type I, conventional portal venous anatomy ( Fig. 5 ), where the MPV bifurcates into the right (RPV) and left portal veins (LPV) with standard branching and the technical success rate exceeds 90%. The predictable anatomy is favorable for TIPS, as it facilitates straightforward access to portal vein branches and the obtuse angle facilitates device advancement and optimizes shunt inflow, reducing the likelihood of dysfunction, with minimal challenges aside from occasional variability in liver size, location, or fibrosis severity. 13
Fig. 5.
Type I: Classical anatomy. The main portal vein (MPV—black arrow) divides into left (LPV—orange arrow) and the right portal veins (RPV—purple arrow). ROV branches into the right anterior (RAPV—red arrow) and posterior (RPPV—yellow arrow) portal vein segments.
Type II, trifurcation ( Fig. 6 ), where the MPV divides into three branches—LPV, right anterior (RAPV), and right posterior portal veins (RPPV). TIPS creation is more challenging due to smaller-caliber targets and acute shunt angles, which complicate device advancement and success rates drop slightly to 75 to 85%. The increased number of target vessels and complex angulation complicate branch selection and increase the risk of puncturing small vessels or bile ducts. Adjunctive imaging techniques and extended procedural times are frequently necessary.
Fig. 6.
Type II: Trifurcation. The MPV (black arrow) divides into the LPV (orange arrow), the RAPV (red arrow), and the RPPV (yellow arrow).
Type III, the right posterior portal vein originates off of the MPV, and the LPV is the terminal branch arising from the RAPV ( Fig. 7 ). Precise targeting of the posterior branch introduces additional complexity, with an increased risk of nontarget punctures due to angulation or vessel overlap. Advanced imaging modalities, such as intravascular ultrasound (IVUS) or cone-beam CT, are often required to navigate these challenges and avoid ischemia.
Fig. 7.
Type III: The right posterior portal vein (yellow arrow) originates from the MPV (black arrow), rather than from the RPV (not seen here); the RAPV (red arrow) originates from the proximal LPV (orange arrow).
Type IV, segment VII as the first branch off the right portal vein ( Fig. 8 ), where the RPV bifurcates into two vessels: one supplying segment VII and the other supplying segments V, VI, and VIII. Similar to Type I, this pattern features a predictable large-caliber target in the main trunk, enabling obtuse shunt angulation and straightforward device advancement, while ensuring effective portal decompression.
Fig. 8.
Type IV: The segment VII branch (green arrow) is a separate branch of the RPV (purple arrow). The LPV (orange arrow) and MPV (black arrow) are also labeled for anatomic reference.
Type V, segment VI as the first branch off the right portal vein ( Fig. 9 ): in this variant, the RPV bifurcates into a branch supplying segment VI and another supplying segments V, VII, and VIII. Like Type IV, this configuration offers a large-caliber right portal trunk in a predictable location, facilitating TIPS creation with optimized inflow and efficient portal decompression.
Fig. 9.
Type V: The segment VI branch (blue arrow) is a separate branch of the RPV (purple arrow). The MPV is also pictured (black arrow) for reference.
Understanding these portal vein variants and their implications is essential for procedural planning, imaging selection, and optimizing technical success in TIPS creation.
Conclusion
Recognizing and understanding variant portal venous anatomy is critical for interventional radiologists performing procedures where navigation across portal veins is necessary such as TIPS, and portal vein embolization. Variations in portal vein anatomy are common and can significantly impact procedural success if not identified and managed appropriately. Preprocedural imaging plays a pivotal role in identifying these variants, allowing for careful planning and modification of techniques to optimize outcomes. As IR continues to evolve, the ability to navigate complex vascular anatomy will remain essential in ensuring patient safety and procedural efficacy.
Conflict of Interest None declared.
The Institutional Review Board Approval Number
Not applicable.
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