Portal Vein Embolization

Hepatocellular Carcinoma

Portal vein embolization was initially proposed in hepatocellular carcinoma (HCC) at least for controlling retrograde tumor thrombus invasion in the portal vein, although today there is little evidence to support this indication. Most HCCs occur in patients with compromised livers, which increases significantly the risk of severe postoperative complications and limits the possibilities for major curative liver resection. Consequently, PVE is actually proposed in selected cases to extend the indications for curative surgery and to increase its safety. Apart from increasing the FRL volume and function, minimizing the sudden increase in portal pressure at resection in these cirrhotic patients may also be an advantage of preoperative PVE.

Liver Metastasis

Curative resection of liver metastases is mainly performed in patients presenting with colorectal primary cancer. Liver metastases are found in 40% to 70% of patients with a colorectal cancer. In about one third of cases, the liver is shown to be the only site of cancer spread, even at autopsy. At the time of diagnosis, resection can be performed in less than 20% of all patients with colorectal liver metastases. The main limitation for resectability is the inability to be curative, while leaving a sufficient residual amount of functional liver parenchyma. Consequently, preoperative PVE may dramatically improve the potential for curative resection of liver metastases by increasing the volume and the function of the FRL. When considering liver metastases from colorectal cancer, it is noteworthy that many patients have been pretreated with chemotherapy. Most chemotherapeutic drugs are toxic to hepatic parenchyma, causing steatosis or steatohepatitis linked to irinotecan or sinusoidal obstruction linked to oxaliplatin. To reduce the risk of hepatic posthepatectomy failure, there is a need to increase the acceptable level of FRL volume to 30% to 40% of the total liver,

Other Indications

Portal vein embolization has been reported before resection of hilar cholangiocarcinoma, multiple benign adenomas (whose dissemination in the liver parenchyma impedes curative surgery), and single huge benign adenomas. PVE has also allowed resection in primary sclerosing cholangitis.

Anatomy and Approaches

A thorough knowledge of hepatic segmentation and portal venous anatomy is essential before performing PVE. The most frequent variation occurs in the supply of the segment V and VIII segments by a middle or left-sided PV branch rather than the main right PV branch. Therefore, two main variations are frequently encountered: (1) trifurcation of the portal vein into the left branch, segments V + VIII branch, and segments VI + VII branch, and (2) bifurcation of the portal vein into a right vein limited to segments VI + VII, and left vein also giving rise to segments V + VIII branch. The operator must also know the plane of the hepatectomy before starting the procedure, because the extent of PVE must mimic the extent of surgery. Moreover, as more and more atypical surgical procedures are performed, several different types of PVE are possible ( Fig. 37.3 ).

Technical Aspects

The procedure may be performed under intravenous sedation and analgesia, but most teams prefer general anesthesia, which provides more comfort for the patient and the operator.

Access can be obtained from a contralateral approach (i.e., puncture of the left portal branch followed by embolization of right portal branches) or an ipsilateral approach (puncture of the right to embolize the right portal branches). The advantage of the contralateral approach is easier catheterization of the right lobe branches, but there is a risk of damage to the FRL. The ipsilateral approach allows for an easier catheterization of segment IV branches when this is required. The drawbacks of the ipsilateral approach are difficulty in accessing the right portal branches retrogradely and the challenge to obtain a good-quality completion portogram, because the catheter has to pass through the embolic material to be placed in the portal vein for the final contrast medium injection. Selecting the access route also depends on the embolic material to be used. Glue cannot be delivered easily from an ipsilateral access, whereas large-caliber embolic materials such as plugs need larger diameter access punctures, which are less risky when these have been obtained from the ipsilateral side. The complication rates of both access routes seem similar and are mainly related to the puncture of unexpected structures such as bile ducts or hepatic arteries. The largest series of contralateral PVE procedures reviewed 188 cases performed in different centers using a contralateral access route as well as N-butyl cyanoacrylate as an embolic material. In the literature, the only factor that increases complications is puncture of the right posterior segment versus puncture of the right anterior segment, thus advocating puncture of the anterior segment when compatible with the location of the PVE to be performed.

When the goal of PVE is occlusion of right PV branches, we prefer access to the portal vein using the contralateral anterior subxiphoid left-sided route, which allows antegrade catheterization of all of the right-sided branches to be embolized safely. The puncture is achieved under ultrasonographic guidance with a 5Fr needle catheter. When branches of segment IV do not need to be occluded, the entry point into the portal venous system may be via the Rex recess. If segment IV is affected by PVE, it is recommended to enter a peripheral segment III branch to facilitate catheterization of segment IV branches. Retrograde catheterization of the main portal trunk for performing portography is the first step of the procedure to identify individual intrahepatic branches and anatomic variations. In all patients with a known or suspected compromised liver, the portal pressure must be measured before embolization because it represents a prognostic parameter. Catheterization of every branch to be embolized is then performed with the 5Fr catheter of the needle catheter device. Depending on individual anatomy, a 1- to 2-cm length and 30- to 90-degree angulated tip is then shaped with steam to make further maneuvers easier. Every main trunk to be occluded is selectively catheterized for performing a distal and free-flow embolization. The degree of selectivity (sectorial, segmental, or subsegmental) before each embolization depends on the individual anatomy and local hemodynamics. The catheter is positioned in each vein to ensure a stable location to provide the best condition for free-flow embolization while preventing inadvertent reflux of embolic material. Massive reflux of embolic agent into the FRL would be catastrophic by either preventing FRL hypertrophy or by causing almost total portal vein occlusion and thereby fatal portal hypertension when the rest of the portal vasculature has already been totally embolized. Consequently, right-sided branches originating close to the portal bifurcation should be hyperselectively catheterized. Caution should also be exercised to avoid reflux into the left lobe portal veins when occluding veins in segment IV. Because of this potential risk, segment IV portal veins should be occluded first for added safety, and particulate embolic agent is preferred to cyanoacrylate. We mostly perform embolization with a mixture of cyanoacrylate and Lipiodol. The safe use of this embolic agent mandates following a very strict technique, but we find it to be a very useful embolic agent for PVE. It allows for complete and durable occlusion. Its radiopacity increases safety at the time of embolization. Histoacryl and Lipiodol are mixed in a ratio of 1 part Histoacryl for 1 to 3 parts Lipiodol; the more Lipiodol in the mixture, the longer the polymerization time of the glue. Consequently, this embolic agent enables distal embolization in every case, because the polymerization time can be adapted for individual hemodynamic variations in different patients. Furthermore, the cyanoacrylate induces a very strong inflammatory reaction, involving vessels as well as bile ducts, which is thought to increase production of hepatotropic factors. The mixture is pushed with isotonic glucose, following the “sandwich technique,” with the volume of every injection of mixture being lower than the catheter. The total dose of Histoacryl will be 1 to 3 mL administered in four to ten successive injections of glue/Lipiodol mixture. Catheter occlusion with repetitive injections of glue is a risk of this technique. Pushing the 0.035-inch glidewire through the catheter still in position, immediately after each injection of glue, minimizes it. This cleans the inner wall of the catheter from the residual glue/Lipiodol mixture and gently pushes it out into the embolized vein under fluoroscopic control. A control portogram is performed at the end of the procedure, and the postembolization portal pressure is recorded. In our experience, the transhepatic tract does not need to be embolized.