Overview
Definition:
Portal vein embolization (PVE) is an interventional radiological procedure designed to induce hypertrophy of the future remnant liver (FRL) prior to major hepatectomy, particularly in cases of extensive liver resection or compromised liver function
It involves occluding a portal vein branch supplying the planned resected liver segment(s), thereby redirecting portal blood flow to the FRL and stimulating its compensatory growth.
Epidemiology:
PVE is employed in a subset of patients undergoing liver resection for various pathologies, including malignancies (hepatocellular carcinoma, colorectal liver metastases), benign tumors, and focal liver lesions
The incidence is directly related to the frequency of challenging hepatectomies requiring FRL hypertrophy
Data suggests PVE is utilized in approximately 5-15% of patients undergoing major liver resections, with varying adoption rates across institutions.
Clinical Significance:
PVE plays a critical role in preventing post-hepatectomy liver failure (PHLF), a major cause of morbidity and mortality after extensive liver resections
By ensuring adequate FRL volume, PVE facilitates sufficient hepatic functional reserve, allowing patients to tolerate the removal of diseased liver tissue
This technique expands the eligibility for potentially curative resections in patients previously deemed unresectable due to insufficient liver volume.
Indications
Indications For Pve:
Absolute indications include planned resection of more than 70% of the liver volume in a healthy liver, or more than 50% in a cirrhotic liver
insufficient FRL volume (<20-25% in healthy liver, <40% in cirrhotic liver) determined by volumetric assessment
and presence of underlying liver disease that might impair regeneration
Relative indications may include situations where ipsilateral portal vein occlusion is planned or in certain cases of synchronous bilateral metastases.
Contraindications:
Absolute contraindications include unresectable primary tumor, extensive extrahepatic disease, uncorrectable coagulopathy, and severe portal hypertension with ascites or variceal bleeding
Relative contraindications might include acute liver failure, severe sepsis, and extensive intrahepatic tumor infiltration that makes complete resection uncertain even after hypertrophy.
Patient Selection:
Careful patient selection is paramount
This involves thorough assessment of liver function (e.g., MELD score, Child-Pugh score, indocyanine green (ICG) retention test), precise volumetric analysis of liver segments using cross-sectional imaging (CT or MRI), and evaluation of the portal venous anatomy
Multidisciplinary team discussion involving surgeons, interventional radiologists, and hepatologists is essential.
Preoperative Preparation
Imaging Assessment:
Pre-PVE imaging includes contrast-enhanced CT or MRI for precise volumetry of the liver segments, assessment of FRL volume, and detailed mapping of portal vein anatomy, including accessory and replaced vessels
Doppler ultrasound can assess portal flow dynamics.
Laboratory Tests:
Routine laboratory tests include complete blood count, liver function tests (AST, ALT, bilirubin, albumin, prothrombin time/INR), coagulation profile, electrolytes, and renal function tests
Indocyanine green (ICG) retention test is crucial for assessing functional liver reserve
a post-treatment ICG value >15% often predicts poor outcomes.
Prophylactic Measures:
Prophylaxis against bacterial infection (e.g., antibiotics) may be considered
Anticoagulation status needs careful management, especially if a transjugular approach is used
Patients should be optimized for general anesthesia and potential complications.
Procedure Steps
Approach Selection:
PVE can be performed via a transjugular or percutaneous transfemoral/transhepatic approach
The transjugular route is often preferred due to lower risk of bleeding and bile leakage, especially in patients with coagulopathy or ascites.
Embolization Technique:
Under fluoroscopic guidance, a catheter is advanced into the target portal vein branch(es)
Embolic agents, such as polyvinyl alcohol (PVA) particles, iodized oil, ethiodized oil, or glue (cyanoacrylate), are injected until stasis in the targeted vessels is achieved
The extent of embolization depends on the planned resection volume and the number of affected portal territories.
Embolization Agents:
Choice of embolic agent depends on the desired duration of occlusion and institutional preference
PVA particles offer particulate embolization, while glue provides more complete and permanent occlusion
The goal is to selectively embolize branches supplying the non-target liver segments to maximally stimulate hypertrophy of the FRL.
Post Embolization Imaging:
Post-procedure imaging (CT or MRI) is typically performed 4-6 weeks after PVE to assess the degree of FRL hypertrophy and confirm exclusion of the embolized segments
A hypertrophy rate of at least 10-20% per week is generally expected.
Postoperative Care And Monitoring
Immediate Post Procedure:
Patients are monitored for complications such as pain, fever, bleeding, and hepatic decompensation
Vital signs and abdominal examination are performed regularly
Pain management with analgesics is essential.
Monitoring For Complications:
Close monitoring for potential complications includes vigilance for signs of liver failure (jaundice, ascites, encephalopathy), portal vein thrombosis, hepatic infarction, and sepsis
Laboratory parameters are rechecked
Doppler ultrasound may be used to assess portal vein patency.
Timing Of Hepatectomy:
The hepatectomy is typically scheduled 4-8 weeks after PVE, once adequate hypertrophy of the FRL is achieved and confirmed by imaging
The optimal timing ensures that the FRL volume and function are sufficient to support the patient post-resection.
Complications
Early Complications:
Early complications include post-embolization syndrome (fever, abdominal pain, nausea, vomiting), transient elevation of liver enzymes, portal vein thrombosis, hepatic infarction, and bleeding at the access site
Biliary complications are rare but can occur with transhepatic approaches.
Late Complications:
Late complications are less common and can include inadequate or asymmetric hypertrophy, development of portal hypertension, and recurrence of tumor in the remaining liver segments if the PVE was performed for malignant disease
Portal cavernoma transformation is a rare long-term sequela.
Management Of Complications:
Post-embolization syndrome is typically managed conservatively with supportive care
Portal vein thrombosis may require anticoagulation
Significant hepatic infarction or liver failure necessitates intensive medical management
Recurrent disease requires prompt oncological intervention.
Prognosis
Factors Affecting Outcomes:
Successful PVE leading to adequate FRL hypertrophy significantly improves outcomes for major hepatectomy
Factors influencing prognosis include the baseline liver function, the degree of hypertrophy achieved, the extent of the planned resection, the underlying liver pathology, and the patient's overall health status.
Success Rates:
Success rates for PVE, defined by significant FRL hypertrophy (e.g., increase of >10% absolute volume or >20% relative volume) and successful subsequent hepatectomy without PHLF, are generally high, ranging from 80-95% in experienced centers
The rate of PHLF post-hepatectomy is significantly reduced in patients who undergo successful PVE.
Long Term Survival:
For malignant conditions, long-term survival is primarily dictated by the oncological outcome and control of the disease
PVE enables potentially curative resections, which are often associated with improved long-term survival compared to unresectable disease
For benign conditions, outcomes are generally excellent post-resection.
Key Points
Exam Focus:
Understand the rationale behind PVE for increasing FRL volume prior to major hepatectomy
Know the indications, contraindications, and contraindications for PVE
Recall the common embolic agents and approaches (transjugular vs
percutaneous)
Be familiar with the expected timeline for hypertrophy and the assessment of PHLF risk.
Clinical Pearls:
Always correlate imaging findings with clinical assessment
ICG retention test is vital for functional assessment
Multidisciplinary discussion is key for optimal patient selection and planning
Monitor for post-embolization syndrome and signs of liver decompensation diligently.
Common Mistakes:
Failing to accurately assess FRL volume pre-PVE
Embolizing the wrong portal vein branches
Inadequate hypertrophy post-PVE
Delaying hepatectomy beyond the optimal window
Underestimating the risk of PHLF in patients with borderline liver function.