The overall goal of this surgical intervention is to achieve rapid hypertrophy of the rat liver by ligation of the portal vein and transection of the parenchyma. This model allows for details physiological and molecular assessments of rapid liver regeneration. The liver regenerates after portal vein ligation.
We found a way of transecting the parenchyma additionally to the portal vein ligation to accelerate that regeneration. This method provides a model for accelerated liver regeneration. It's a method that's used in human surgery for patients with borderline resectable liver tumors.
Once the animal is fully anesthetized and prepared for surgery, shave the abdomen along the midline from the xiphoid to the genitals using small animal hair clippers. Thoroughly remove the hair within two centimeters of the midline. After disinfecting the skin, make an incision through the abdominal wall.
Then retract both walls and the xiphoid with 3-0 silk stay sutures. Next using self-made small wire retractors, retract the stomach, colon and small bowel away from the hepatoduodenal ligament. Thus access the portal vein.
Now dissect the portal vein bluntly. Lift the peritoneum with the micro forceps and slowly peel it medially. Dissect out the portal vein branches in the following sequence.
First, the right posterior branch. Second, the left lateral and left median branch together. And third, the caudate branch.
Next carefully peel off the peritoneum using small movements to avoid tearing the small arterial branches to the liver lobes that run directly below. Once the main portal vein is denuded, encircle the branches with slow forward pushing and spreading movements. Avoid pushing against resistance to prevent tearing an artery or vein.
This is an essential part of the procedure. You have to avoid pushing against resistance. But usually once you've taken the peritoneal surface off, the microsurgical right angles slide quite easily around the portal vein branches.
In case of bleeding apply pressure for at least one minute with a sterile cotton swab, and then reassess. Repeat this maneuver several times, if necessary. If the bleeding does not stop, then sacrifice the animal.
Next, dissect the right posterior lobe branch. First carefully move the artery that runs directly across the lobe branch. Then using curved micro forceps, pull the artery cranially together with the peritoneum to expose the right portal vein branch.
Now ligate the right posterior lobe branch using 6-0 silk. Observe the right posterior lobe. It will go pale after the ligation.
Next, dissect the LLL and LML branches. They share a common trunk. Avoid injuring the arteries that run within the peritoneal layer leading to these branches.
Peel the peritoneum back carefully to keep those arteries intact. Then dissect the somewhat separate caudate lobe branch. The portal vein leading to it takes off from the main portal vein distally and medial to the right lobe branch.
This is unlike larger animals where the branches are strictly inferior. Lift the hepatoduodenal ligament with bile duct and the arteries from the main portal vein to dissect out and encircle the caudate lobe branch. Use curved micro forceps and approach the lobe laterally.
Then ligate using 6-0 silk. This lobe will also turn pale after the ligation. Now observe the appearance of a distinct demarcation between the right and left median lobe.
This forms due to exclusive portal vein profusion of only the RML. The surgery can be stopped here for the portal vein ligation model. To proceed with the transection, use a non-sticking bipolar silver forceps with a very fine neurosurgical tip.
First, pre-cauterize the tissue by creating a short cauterization strip along the demarcation line. Next use scissors to carefully cut the pre-cauterized tissue. Cut deep enough to be as close to the vena cava as possible, which runs intrahepatically.
Damaging the vena cava usually results in sacrificing the animal, so be extra careful. Different techniques have been used to transect the parenchyma. We found that using a silver forceps with fine tips, pre-cauterizing the liver tissue, then followed by the scissors to cut through it works the best for minimal blood loss.
After the transection, pat the abdomen dry and make sure that there is no bleeding. Before closing the animal, make sure that the small bowel is repositioned correctly. Then close the peritoneum and the abdominal wall by placing 3-0 silk sutures using SH-1 needles.
Lastly, use 5-0 Maxon to suture the skin. Post surgery there are distinctly different growth kinetics associated with the PVL without transection and the PVL with transection, which is also known as ALPPS. Daily volumetric measurements of the liver show that by day three there is only a 100%increase in volume after PVL, but there is a 200%increase in volume after ALPPS.
After watching this video you should have a pretty good idea on how to perform a ligation of 75%of the portal inflow into the parenchyma, plus a transection. Once mastered, the procedure should not take longer than 45 minutes. While attempting this procedure it's important to have both an anesthesiologist and a surgeon experienced with volatile anesthesia present.
Following along the general lines of this procedure you can attempt other types of transection techniques. For example, partial transection or ligation or radio frequency oblation to figure out how important the amount or type of transection is to induce rapid hypertrophy. Don't forget that after surgery in rodents, it's important to assess them for pain and provide sufficient analgesia.
