Трансплантация печени: методы, этапы и современные достижения.

Type of organ transplantation

Before transplantation, liver support therapy might be indicated (bridging to transplantation). Artificial liver support like liver dialysis or bioartificial liver support concepts are currently under preclinical and clinical evaluation. Virtually all liver transplants are done in an orthotopic fashion; that is, the native liver is removed and the new liver is placed in the same anatomic location. The transplant operation can be conceptualized as consisting of the hepatectomy (liver removal) phase, the anhepatic (no liver) phase, and the postimplantation phase. The operation is done through a large incision in the upper abdomen. The hepatectomy involves division of all ligamentous attachments to the liver, as well as the common bile duct, hepatic artery, hepatic vein and portal vein. Usually, the retrohepatic portion of the inferior vena cava is removed along with the liver, although an alternative technique preserves the recipient's vena cava ("piggyback" technique). The donor's blood in the liver will be replaced by an ice cold organ storage solution, such as UW (Viaspan) or HTK, until the allograft liver is implanted. Implantation involves anastomoses (connections) of the inferior vena cava, portal vein, and hepatic artery. After blood flow is restored to the new liver, the biliary (bile duct) anastomosis is constructed, either to the recipient's own bile duct or to the small intestine. The surgery usually takes between five and six hours, but may be longer or shorter due to the difficulty of the operation and the experience of the surgeon. The large majority of liver transplants use the entire liver from a non living donor for the transplant, particularly for adult recipients. A major advance in pediatric liver transplantation was the development of reduced size liver transplantation, in which a portion of an adult liver is used for an infant or small child. Further developments in this area included split liver transplantation, in which one liver is used for transplants for two recipients, and living donor liver transplantation, in which a portion of a healthy person's liver is removed and used as the allograft. Living donor liver transplantation for pediatric recipients involves removal of approximately 20% of the liver (Couinaud segments 2 and 3). Further advance in liver transplant involves only resection of the lobe of the liver involved in tumors and the tumor free lobe remains within the recipient. This speeds up the recovery and the patient stay in the hospital quickly shortens to within 5–7 days. Radiofrequency ablation of the liver tumor can be used as a bridge while awaiting liver transplantation.

Between removal from donor and transplantation into the recipient, the allograft liver is stored in a temperature cooled preservation solution. The reduced temperature slows down the process of deterioration from normal metabolic processes, and the storage solution itself is designed to counteract the unwanted effects of cold ischemia. Although "static" cold storage method has long been standard technique, various dynamic preservation methods are under investigation. For example, systems which use a machine to pump blood through the explanted liver (after it is harvested from the body) during a transfer have met some success (see Research section for more).

Living donor liver transplantation (LDLT) has emerged in recent decades as a critical surgical option for patients with end stage liver disease, such as cirrhosis and/or hepatocellular carcinoma often attributable to one or more of the following: long term alcohol use disorder, long term untreated hepatitis C infection, long term untreated hepatitis B infection. The concept of LDLT is based on (1) the remarkable regenerative capacities of the human liver and (2) the widespread shortage of cadaveric livers for patients awaiting transplant. In LDLT, a piece of healthy liver is surgically removed from a living person and transplanted into a recipient, immediately after the recipient's diseased liver has been entirely removed. Historically, LDLT began with terminal pediatric patients, whose parents were motivated to risk donating a portion of their compatible healthy livers to replace their children's failing ones. The first report of successful LDLT was by Silvano Raia at the University of Sao Paulo Faculty of Medicine in July 1989. It was followed by Christoph Broelsch at the University of Chicago Medical Center in November 1989, when two year old Alyssa Smith received a portion of her mother's liver. Surgeons eventually realized that adult to adult LDLT was also possible, and now the practice is common in a few reputable medical institutes. It is considered more technically demanding than even standard, cadaveric donor liver transplantation, and also poses the ethical problems underlying the indication of a major surgical operation (hemihepatectomy or related procedure) on a healthy human being. In various case series, the risk of complications in the donor is around 10%, and very occasionally a second operation is needed. Common problems are biliary fistula, gastric stasis and infections; they are more common after removal of the right lobe of the liver. Death after LDLT has been reported at 0% (Japan), 0.3% (USA) and <1% (Europe), with risks likely to decrease further as surgeons gain more experience in this procedure. Since the law was changed to permit altruistic non directed living organ donations in the UK in 2006, the first altruistic living liver donation took place in Britain in December 2012. In a typical adult recipient LDLT, 55 to 70% of the liver (the right lobe) is removed from a healthy living donor. The donor's liver will regenerate approaching 100% function within 4–6 weeks, and will almost reach full volumetric size with recapitulation of the normal structure soon thereafter. It may be possible to remove up to 70% of the liver from a healthy living donor without harm in most cases. The transplanted portion will reach full function and the appropriate size in the recipient as well, although it will take longer than for the donor. Living donors are faced with risks and/or complications after the surgery. Blood clots and biliary problems have the possibility of arising in the donor post op, but these issues are remedied fairly easily. Although death is a risk that a living donor must be willing to accept prior to the surgery, the mortality rate of living donors in the United States is low. The LDLT donor's immune system does diminish as a result of the liver regenerating, so certain foods which would normally cause an upset stomach could cause serious illness.

In children, living liver donor transplantation has become very accepted. The accessibility of adult parents who want to donate a piece of the liver for their children/infants has reduced the number of children who would have otherwise died waiting for a transplant. Having a parent as a donor also has made it a lot easier for children – because both patients are in the same hospital and can help boost each other's morale.

Living donor transplantation is a multidisciplinary approach. All living liver donors undergo medical evaluation. Every hospital which performs transplants has dedicated nurses that provide specific information about the procedure and answer questions that families may have. During the evaluation process, confidentiality is assured on the potential donor. Every effort is made to ensure that organ donation is not made by coercion from other family members. The transplant team provides both the donor and family thorough counseling and support which continues until full recovery is made. All donors are assessed medically to ensure that they can undergo the surgery. Blood type of the donor and recipient must be compatible but not always identical. Other things assessed prior to surgery include the anatomy of the donor liver. However, even with mild variations in blood vessels and bile duct, surgeons today are able to perform transplantation without problems. The most important criterion for a living liver donor is to be in excellent health.

Like most other allografts, a liver transplant will be rejected by the recipient unless immunosuppressive drugs are used. The immunosuppressive regimens for all solid organ transplants are fairly similar, and a variety of agents are now available. Most liver transplant recipients receive corticosteroids plus a calcineurin inhibitor such as tacrolimus or ciclosporin, (also spelled cyclosporine and cyclosporin) plus a purine antagonist such as mycophenolate mofetil. Clinical outcome is better with tacrolimus than with ciclosporin during the first year of liver transplantation. If the patient has a co morbidity such as active hepatitis B, high doses of hepatitis B immunoglubins are administered in liver transplant patients. Due to both the pharmacological immunosuppression and the immunosuppression of underlying liver disease, vaccinations against vaccination preventable diseases are highly recommended before and after liver transplantation. Vaccine hesitancy in transplant recipients is less than in the general population. Vaccinations are preferably administered to the recipient before the transplant, as post transplant immunosuppression leads to reduced vaccine effectiveness. Liver transplantation is unique in that the risk of chronic rejection also decreases over time, although the great majority of recipients need to take immunosuppressive medication for the rest of their lives. It is possible to be slowly taken off anti rejection medication but only in certain cases. It is theorized that the liver may play a yet unknown role in the maturation of certain cells pertaining to the immune system. There is at least one study by Thomas E. Starzl's team at the University of Pittsburgh which consisted of bone marrow biopsies taken from such patients which demonstrate genotypic chimerism in the bone marrow of liver transplant recipients.

The prognosis following liver transplant is variable, depending on overall health, technical success of the surgery, and the underlying disease process affecting the liver. There is no exact model to predict survival rates; those with transplant have a 58% chance of surviving 15 years. Failure of the new liver (primary nonfunction in liver transplantation or PNF) occurs in 10% to 15% of all cases. These percentages are contributed to by many complications. Early graft failure is probably due to preexisting disease of the donated organ. Others include technical flaws during surgery such as revascularization that may lead to a nonfunctioning graft.

As with many experimental models used in early surgical research, the first attempts at liver transplantation were performed on dogs. The earliest published reports of canine liver transplantations were performed in 1954 by Vittorio Staudacher at Opedale Maggiore Policlinico in Milan, Italy. This initial attempt varied significantly from contemporary techniques; for example, Staudacher reported "arterialization" of the donor portal vein via the recipient hepatic artery, and use of cholecystostomy for biliary drainage. The first attempted human liver transplant was performed in 1963 by Thomas Starzl, although the pediatric patient died intraoperatively due to uncontrolled bleeding. Multiple subsequent attempts by various surgeons remained unsuccessful until 1967, when Starzl transplanted a 19 month old girl with hepatoblastoma who was able to survive for over one year before dying of metastatic disease. A randomized controlled clinical trial comparing normothermic machine preservation with conventional cold storage showed less donor liver injury, less discarded donor livers (due to suboptimal condition), better early function, and longer preservation times compared with static cold stored livers. Graft survival and patient survival after transplant were similar with both approaches. Machine perfusion prior to transplant is associated with decreased tissue re perfusion ischemic injury (a process in which liver cells are damaged as a statically stored liver is re perfused after transplant) as well as a decreased risk of intrahepatic biliary strictures.

The high incidence of liver transplants given to those with alcoholic cirrhosis has led to a recurring controversy regarding the eligibility of such patients for liver transplant. The controversy stems from the view of alcoholism as a self inflicted disease and the perception that those with alcohol induced damage are depriving other patients who could be considered more deserving. It is an important part of the selection process to differentiate transplant candidates who have alcohol use disorder as opposed to those who were susceptible to non dependent alcohol use. The latter who gain control of alcohol use have a good prognosis following transplantation. Once a diagnosis of alcoholism has been established, however, it is necessary to assess the likelihood of future sobriety.

Historically, HIV was considered an absolute contraindication to liver transplantation. This was in part due to concern that the infection would be worsened by the immunosuppressive medication which is required after transplantation. despite his own oncologist at Cedars Sinai having recommended that he use the cannabis for his pain and chemotherapy. Dr. Steven D. Colquhoun, director of the Liver Transplant Program, said that the hospital "must consider issues of substance abuse seriously", but the transplant center did not seriously consider whether Mr. Smith was "using" cannabis versus "abusing" it. In 2012, Cedars Sinai denied a liver transplant to a second patient, Toni Trujillo, after her Cedars Sinai doctors knew and approved of her legal use of medical cannabis. In both cases, the patients acceded to the hospital's demand and stopped using cannabis, despite its therapeutic benefits for them, but were both sent back to the bottom of the transplant list. Smith's death inspired Americans for Safe Access to lobby for the California Medical Cannabis Organ Transplant Act (AB 258), which was enacted in July 2015 to protect future patients from dying at the hands of medical establishments prejudiced against the legal use of medical cannabis.