Portal Vein Embolization
Portal Vein Embolization (PVE) is a specialized medical procedure designed to enhance the safety of extensive liver surgeries. It involves the strategic blocking of a portion of the portal vein, redirecting blood flow towards the future liver remnant (FLR). By stimulating growth in the FLR, PVE allows for more substantial liver resections while minimizing the risk of post-operative complications. This technique is particularly valuable for patients with compromised liver function and requiring removal of a significant portion of their liver due to tumors or other conditions.
| Factors | Description |
|---|---|
| Indications for PVE | 1. Percentage of resected liver - Normal individuals > 70-75% - Compromised liver (CLD, fibrosis) > 60-65% 2. Indocyanine green (ICG) clearance test - ICG plasma 15-min retention rate > 15–20 % in combination with a large liver resection |
| Absolute Contraindications | 1. Extensive ipsilateral tumor thrombus 2. Clinically evident portal hypertension (as a contraindication to surgery) |
| Relative Contraindications | 1. Mild portal hypertension or advanced fibrosis 2. Uncorrectable coagulopathy 3. Renal insufficiency |
| Mechanism | 1. Atrophy-hypertrophy complex - Controlled Liver Hypertrophy 2. Degree of hyperplasia ∝ Degree of injury 3. Greatest hypertrophy occurs in the periportal zone, with a decreasing gradient toward the hepatic vein |
| Portal Anatomy Variation | 1. Portal Trifurcation 2. Portal Quadfurcation 3. Bifurcation of MPV into RPPV and LPV. RAPV arising from LPV 4. Complete absence of RPV |
| Pre-Procedural Workup | 1. CT scans for liver volumes and Portal anatomy 2. LFT (T. Bil < 3mg/dl) 3. Absolute volumes used for FRL % calculation 4. TELV calculation using CT volumetry or sFRL |
| Total estimated volume (TELV) | 1. Introduced to overcome errors in traditional volumetry. 2. Correlates linearly with body size and weight (in adults without chronic liver disease). 3. Formula for TELV based on BSA: TELV = -794 + 1267 × BSA |
| Minimum Standardized Future Liver Remnants (sFLR) | 1. Normal Liver - 20% 2. Chemotherapy-Related Injury - 30% 3. Chronic Liver Disease - 40% |
| Standardized FLR (sFLR) Volume | 1. Ratio of CT-measured FLR volume to TELV based on BSA. 2. Represents the percentage of TELV remaining after resection. |
| 1. Patients with anticipated sFLR below the minimum threshold undergo CT volumetric analysis before and after PVE. 2. If post-PVE sFLR remains below the threshold, additional time may be needed, especially in patients with impaired liver regeneration. 3. Rapid regeneration is unlikely if sFLR remains small 3 weeks after PVE in patients without liver disease. |
|
| Vascular access | 1. Transhepatic Ipsilateral 2. Contralateral (access is obtained by puncture through the FLR) 3. Transileocolic (right lower quadrant incision is made and a vascular sheath introduced directly into an ileocolic venous branch) |
| Catheter choice | Reverse curve catheters for acute angles in segmental branches |
| Embolic Agent | 1. PVA particles + coils 2. Gelatin sponge + lipiodol 3. N-butyl cyanoacrylate mixed lipiodol + coils 4. Fibrin glue/Beriplast + lipiodol 5. Ethanol + lipiodol 6. Others (Vascular plug in combination with NBCA mixed lipiodol) |
| Goal of PVE | Achieve complete portal occlusion of targeted segments |
| Targeted segments | Right lobe (commonly targeted) or right lobe plus segment 4 |
| Technical success rate | 99.3% |
| Clinical Success Rate | 96.1% |
| Time required for Hypertrophy after PVE | 1. Normal liver - 2 to 4 weeks 2. Cirrhotic liver - ≥4 weeks. |
| Sequential Arterial and Portal Embolization | 1. The arterial phase precedes the portal phase to maximize the growth potential of the FLR. 2. Arterial embolization induces ischemia (lack of blood supply) in the tumor-bearing regions. 3. This stimulates the liver to release growth factors, promoting hypertrophy of the non-tumor segments. 4. FLR (TACE+PVE) > FLR (PVE) 5. After PVE alone, hepatic arterial flow within the embolized segment increases (termed the hepatic artery buffer response), which can lead to an accelerated growth of tumors. |
| Complications after PVE | Minor Complications - Fever - Elevation of Transaminase (comes to normal levels in 7-10 days) - Abdominal Discomfort/Pain/Nausea - Ileus Major Complications - Portal Thrombosis - Embolization of Nontarget Vessels - Liver Hematoma - Infection/Abscess - Intra-abdominal Bile Leakage |
| Complications after Surgery | Major Complications - Liver Failure - Portal Thrombosis - Bile Leakage Minor Complications - Ascites - Pleural Effusion |
1. Van Lienden, K P et al. “Portal vein embolization before liver resection: a systematic review.” Cardiovascular and interventional radiology vol. 36,1 (2013): 25-34. doi:10.1007/s00270-012-0440-y
2. May, Benjamin J, and David C Madoff. “Portal vein embolization: rationale, technique, and current application.” Seminars in interventional radiology vol. 29,2 (2012): 81-9. doi:10.1055/s-0032-1312568
3. Kollmar O, Corsten M, Scheuer C, Vollmar B, Schilling M K, Menger M D. Portal branch ligation induces a hepatic arterial buffer response, microvascular remodeling, normoxygenation, and cell proliferation in portal blood-deprived liver tissue. Am J Physiol Gastrointest Liver Physiol. 2007;292(6):G1534–G1542.