Preoperative Portal Vein Embolization: An Approach to Improve the Safety of Major Hepatic Resection

Liver Regeneration

The liver is responsible for several diverse metabolic functions, including detoxification of ingested materials, protein synthesis, bile production, and glycogen storage. Despite its substantial workload, the liver is a fairly mitotically inactive organ—under normal circumstances, only 0.0012% to 0.01% of hepatocytes are undergoing replication at any given time.19, 20 In the setting of hepatic injury or resection, however, liver cells have an enormous capacity for regeneration that is directly

Rationale for PVE

The rationale for performing PVE before major hepatic resection was initially described by Makuuchi et al.¹³ The investigators sought to demonstrate that PVE would limit the increase in portal venous pressure otherwise observed at the time of hepatic resection by redirecting portal venous flow to the FLR before surgery. By separating the possible damage caused by increased portal venous pressure from that of any direct trauma inflicted upon the FLR during the resection, they hoped to reduce

FLR Assessment

Resection of more than 60% of the functional mass of a diseased liver or 80% of that of an otherwise-normal liver increases the likelihood of postoperative complications. PVE is thus indicated when the anticipated FLR is 40% or less in a diseased liver or 20% or less in a healthy liver.3, 4, 34 To make this determination, contrast-enhanced computed tomography (CT) with volumetry is needed. With such imaging, the liver segments are demarcated by the locations of the hepatic and portal veins, and

Technical Aspects of PVE

To divert portal blood flow to the FLR, multiple varied embolic agents and 3 standard technical approaches have been described. The goal is to achieve as complete embolization of the portal branches as possible to ensure sufficient hypertrophy of the FLR and avoid recanalization of the occluded veins.³⁴ In addition, embolization of all the portal branches supplying the area to be resected must be achieved to prevent formation of intrahepatic portoportal collateral vessels.⁴³

A number of embolic

Indications

As mentioned previously, multiple factors determine whether PVE will be beneficial for a given patient. First, an evaluation for underlying liver disease must be made to ascertain the necessary FLR volume after resection—those patients with an otherwise-healthy liver will not require as great an FLR mass as those with cirrhosis. Next, the patient's body size must be taken into account. Larger patients will inevitably require larger FLRs than smaller patients under otherwise similar

Contraindications

The only absolute contraindication to PVE is severe portal hypertension, which precludes hepatectomy. In many centers, portal venous pressures are measured before and after PVE in patients with chronic liver disease because preoperative core needle biopsy is often unable to successfully gauge the degree of hepatic fibrosis.⁶² Mild portal hypertension is not a contraindication to PVE in the setting of otherwise normal liver function tests.

For tumor obstruction of the portal system in the liver

Outcomes in Patients with Chronic Liver Disease

Chronic liver disease leads to decreased rates of hepatic regeneration after PVE (9 cm³/d at 2 weeks vs 12-21 cm³/d in normal liver);24, 30 as a result, adequate hypertrophy may require more than 4 weeks in these patients. The actual increase in FLR volume after PVE is also smaller in this group, ranging from 28% to 46%.²⁴ This decreased response to hepatotropic agents is believed to result from limited portal blood flow caused by parenchymal fibrosis or to the diseased nature of the

Outcomes in Patients with Otherwise-Healthy Livers

In patients with cirrhosis, extended hepatectomy is seldom feasible because of the small size of the liver remnant, even after PVE. In contrast, patients without underlying liver disease who present with hilar cholangiocarcinoma or hepatic metastases often warrant extended resection (ie, the right liver plus segment 4 ± segment 1 or, less frequently, the left lobe plus segments 5 and 8 ± segment 1). In these settings, particularly with extended right hepatectomy, the FLR volume is frequently

Future Prospects

The utility of PVE is constantly evolving through the use of newer embolic agents, the refinement of existing techniques, and the development of adjunctive procedures. These advances have the potential not only to improve the efficacy of PVE but also to widen the scope of its use. For instance, a persistent hurdle for PVE has been the limited regenerative capacity in patients with underlying liver disease. Such patients are also predisposed to the development of insulin resistance, which

Conclusions

Preoperative PVE is a useful technique to increase the size and functional capacity of the anticipated liver remnant before hepatectomy. PVE allows hepatic resection in patients who would otherwise be considered unresectable as the result of small remnant volume and decreases their risks of postoperative morbidity and mortality. Current guidelines suggest PVE in those patients with underlying liver disease and an anticipated FLR/TELV no greater than 40% or those with otherwise normal liver