| BACKGROUND:Liver cancer that causes of death in the third is one of the most common malignant tumor and worldwide each year, nearly one million people die of the disease. The hepatic surgery undergoes evolutionary process including hepatic wedge resection, regular hepatic lobectomy, anatomical hepatic lobectomy. With the high-speed development of modern technology and information age, the hepatic surgery steps into a precise liver resection era with the help of modern technology platform.In essence, further development of precise liver resection (PLR) not oly relies on the merge of computer technology, information science, biomedical engineering and digital image technology, but also the precise investigation concerning pathophysiology. This enables the clinical medicine in decision-making and implementation more scientific and accurate. The only way to achieve this is digital research based on physiology.Although the history of liver resection has been many years, it is not clear how much liver volume excised is too much and the basis that we rely on to determine the minimum amount of liver tissue to meet the demand of human body metabolism. Most doctors estimate that according to clinical experience and different medical units get different judgments, for example, the University of Tokyo uses Machuchi criterion to estimate preoperative patients, which consistes of ascites, bilirubin and ICG15minutes retention rate. This criterion which effectively avoids the inappropriate surgical intervention, can evaluate the liver reserve function systemically and get corresponding liver surgical treatment stepwise. According to the report, there has been1056successful operations without death based on the criterion. But there is no experimental basis and it is still uncertain whether all the suitable patients can receive radical resection.The liver is the only organ that can regenerate after partial resection and recover to its initial state. It is meaningful to study how to achieve a considerable liver from a smaller liver tissue through regeneration. To date, most scholars agreed on that the remenant liver volume should be more than25%in order to maintain normal function. However,some cases challenged this notion. Furthremore, some animal models showed that90%heptoectomy without protal shunt could keep total alive. This indicated the huge promising regeneration ability. With the development of modern heprosurgery, various heptoectomy could be operated technically. Therefore, it is particularly urgent to solve the basic problem of" minimal volume of liver " after subtotal hepatectomy and explore measures and foundations of how to reduce the safe minimal liver volume, which will be helpful to broaden the indications of liver resection, prevent postoperative liver failure and enhance safety and accuracy of liver resection.The present study aims to conduct a steady experimentla animal model of heptoectomy of pig. Further study will be investigated into the maximum volume of remenant liver to maintain normal physiology after heptoectomy. This provides a meaningful basis for minimum-safe-liver vlomume in human beings.METHODS:Bench dissection of10cadaveric porcine livers was performed to calculate each liver lobe volumes. Twenty one pigs were subjected to different liver resection volumes of77-82%(20%-Rgroup, n=7),83-87%(15%-Rgroup, n=7), and88-92%(10%-Rgroup, n=7) using the hilar pedicle suture technique. The survival rate, hemodynamic change,LPS or inflammatory response, the injury and regeneration of the residual liver was observed after surgery. RESULTS:The liver remnant in20%-Rgroup with about4times baseline PVF per unit volume, subjected to mild portal overflow injury and regenerate successfully, whereas in the15%R-group with about5.6times baseline PVF,3animals were alive on postoperative day (POD)14; in the10%-Rgroup with more than6times baseline PVF, subjected to severe portal overflow injury, none survived to POD14. The14d-survival rates were100%,42.8%, and0respectively in20R-group.15%-R group,10%-R group, were significantly different.CONCLUSION:The deaths of animals in the group with15%of liver remnant supports the hypothesis that the15%of liver remnant represents a critical residual liver parenchyma in pigs, the safe MRLV should beyond15%of total liver volume, and the utmost PVF the liver remnant can sustain should less than5.6times baseline. BACKGROUND:The earliest rat experiment demonstrated that the vascular bed of remnant liver was dramatically reduced after major hepatectomy and this resulted in hyperfusion damage of portal vein.Elevated portal pressure after hepatectomy is frequently observed clinically whether in partial hepatectomy or living donor liver transplantation.From being suffered from the Small-for-size Syndrome (SFSS) after partial hepatectomy or living donor liver transplantation, people gradually paid attention to the significance of portal pressure. Elevated portal pressure leads to massive ascites, gastrointestinal hemorrhage and ventosity. Elevated portal pressure and hyperfusion are considered as the most important factor at postoperative hepatic insufficiency.Immunologic mechanisms and ischemical reperfusion injury partly contribute to the distinction between living donor liver transplantation and major hepatectomy.Therefore,it is necessary to invstigate mechanisms associated with organ dysfunction induced by elevated portal pressure after heptoectomy.The past related reports suggested that elevated portal pressure was observed in patients whose liver sparing was less than30%.The postoperative liver also accepts the original blood flow.However, the loss of hepatic sinusoid vascular results in elevated pressure, accompanying the faster blood flow rate. Researches found that the tolerance limit of newly increased blood was20%. As a result, residual hepato or living donor liver graft was damaged in varying degrees due to relatively increased blood flow. In liver,the pressure of a small branch of portal vein is the highestand it will be inevitablely firstly damaged.To alleviate damage caused by portal hyperfusion postoperatively, portal caval shunt or ligation of splenic artery is commonly used clinically. The blood flow of pig spleen is so small that the ligation of splenic artery has limited effet to decrease portal pressure. Therefore, portal caval shunt was widely investgated clinically or in animal experiments. Hyperperfusion of blood damages the remanent liver. Shimamura et al suggested that perfusion pressure should be less than15mmHg to avoid liver failure caused by hyperperfusion.In addition, no researches found the advisable flow volume, as well as the impact on high portal pressure, intestinal absorption of endotoxin or bacterial translocation.Large animal models provide a pathiphysiology method to discuss the disease clinically and it is easier to apply to human environment.Our previous study proved that the Bama small pig (Guangxi, China),which was inbred breeding, acted as an ideal experimental animal and was widely used in liver transplantation.Small pig liver was applied to anatomy research. Hepatis transfixion simplified the surgery procedures of pig heptoectomy.All kinds of heptoectomy could be acomplished wighout more than50ml-blood-flow. This stablized the animal models for further experiment.It was previously reported that the safe minimal liver remnant (MLR) after hepatic inflow occlusion (HIO) for20min should be more than30-35%of the total liver volume (TLV) in porcine hepatectomy. Although a mesocaval shunt (MCS) can relieve the portal hyperperfusion due to the "small-for-size" syndrome resulting from small graft or liver remnants, there are no reports regarding its efficacy. The present study aimed to determine the maximum volume that can be diverted by an MCS in a stable pig model.METHODS:All20animals underwent successful HIO for20min and were then randomly divided into three groups, including a30%-group, in which30%of the TLV remained; a25%+S-group, in which25%of the TLV remained and a MCS was used; and a20%+S-group, in which20%of the TLV remained and a MCS was used. The survival rates, kinetic portal vein pressure (PVP), and changes in various serum and tissue parameters in the three groups were investigated.RESULTS:The fourteen-day survival rate in the25%+S-group was significantly higher compared with that in the30%-group and20%+S-group (85.7%vs.16.7%vs.42.9%, respectively, P=0.018).。Changes in the serum parameters and histological findings in the25%+S-group were significantly less than those in the other two groups (P<0.05for both comparisons).CONCLUSION:The decompression of the portal vein by a MCS can decrease overflow injury and make20-25%of the liver remnant safe; thus, the safe MRV was reduced to approximately10%of the TLV and provides a reference for clinical use. |
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