الفهرس 
EVOLUTION OF LIVER TRANSPLANTATIONOnly 14 pages are availabe for public view
 |  | from | 137 |  |  |
| | | from | 137 | | |
Abstract
Liver transplantation is identified worldwide as a definite therapy for both acute and chronic end-stage liver disease (Akun R et al, 2012). Unlike the kidney and pancreas, the liver is transplanted in an orthotopic position (OLT). Living donor liver transplantation (LDLT) has evolved to address the shortage of deceased donors. However, compared to deceased donor liver transplantation, LDLT is technically demanding and carries a higher risk of developing vascular complications. Sophisticated postoperative care with multidisciplinary team involvement in LDLT can achieve low hospital morbidity and mortality rates.
Vascular complications in liver transplantation can endanger graft viability and threaten outcomes for patients and allografts; early recognition is crucial. Diminished liver blood supply may lead to early graft failure; therefore, intra or early post-operative diagnosis is lifesaving (Steinbrück K et al, 2011). Clinical and laboratory findings in the post-transplantation period can raise the suspicion of a vascular complication. Definitive diagnosis of these complications is established by imaging modalities. Doppler US, contrast-enhanced ultrasound (CEUS) and CTA (CT angiography) are noninvasive techniques for surveillance with conventional angiography performed for diagnostic and interventional purposes (Pérez-Saborido B etal,2011).
Hepatic artery complications after liver transplantation represent an important cause of morbidity and mortality, including hepatic artery thrombosis (HAT), hepatic artery stenosis (HAS), pseudo-aneurysm, and arteriovenous fistula (Bekker J et al, 2009). Of these, hepatic artery thrombosis (HAT), which occurs in 3% to 9% of adult transplant recipients, is the most frequent arterial complication in OLT (Pawlak J et al, 2000).
The risk factors for hepatic arterial complications after LT include the narrow diameter of the hepatic artery which makes the reconstructive procedure more difficult and complicated in both adult and pediatric LTs, microsurgical techniques can contribute to reduction of the incidence of hepatic arterial complications (HATANO E et al,1997). The incidence of arterial thrombosis has been reduced dramatically from 25% without a microscope to 0∼3.8% with a microscope (Wei WI et al,2004) .Besides artery diameter, greater donor age (>60 yr), prolonged cold ischemic time, prolonged warm ischemic time, prolonged operation time , the combination of a cytomegarovirus positive donor and negative recipient , ABO incompatibility, and Roux-en-Y biliary reconstruction have been reported as risk factors for adult LT (Silva MA e al,2006).
Various therapeutic options for managing HAT, including arterial reconstruction, surgical thrombectomy, hepatic artery stenting and radiologically guided thrombolysis, are available. Retransplantation is restricted by both graft availability and the patient’s general condition (Jiang L. et al, 2002).
Portal vein stenosis (PVS) and portal vein thrombosis (PVT) are among the most serious vascular complications leading to graft failure in adult LDLT with a reported incidence of 4% to 9 %.(Song S et al,2016).
Several previous studies reported the risk factors for portal vein complications (PVCs), which include pretransplant PVT, smaller graft size, older donor age, splenectomy, use of jump grafts or interposition cryo-preserved grafts for portal vein (PV) reconstruction, and postoperative transfusion of erythrocytes or platelets. (Linares I et al,2018). There are many other factors that can affect the success of management of PVT such as, the characteristics of portal venous thrombus (whether acute or chronic), degree (partial or complete), and also, degree of extension to the splanchnic venous system (Tao YF et al, 2009).
One of the crucial factors for a LDLT with a satisfactory outcome is a sufficient hepatic vein outflow; without adequate venous drainage and outflow, the graft will be liable for congestion and catastrophic sequele in both acute and chronic forms (Kim et al., 2007).
Hepatic venous outflow obstruction can be caused by either stenosis, thrombosis or presence of both stenosis and thrombosis at the anastomotic site or sites if there are multiple anastomoses.one of the crucial factors for prevention of anastomotic stricture is the design and shape of the orifice of the hepatic vein in both the graft and the recipient. Regarding hepatic vein stenosis, several potential mechanisms could be encountered, intra-operative improper technique is by far the most likely cause such as tight anastomoses causing purse-string phenomenon, stitches including the back wall of the vein or additional hemostatic stitches. Also the structural stenosis of the hepatic vein in the post-operative period due to enlargement of the graft during the process of regeneration can also be one of the factor (Otte JB et al, 1990).
Conventional gray-scale and Doppler ultrasound, contrast-enhanced ultrasound (CEUS) play important roles in identifying vascular complications in the early postoperative period and during follow-up. Advancements within the field of interventional radiology (IR) have allowed many of the complications and transplantation to be treated in a minimally invasive fashion.
Detailed and accurate preoperative imaging combined with intra-operative Doppler assessment with early and early regular post-operative follow up imaging and careful surgical dissection allows identifying and performing efficient vascular anastomosis significantly reduce vascular complications. Although arterial and venous problems are not common among the population of liver transplant recipients, they are of a critical importance as they can gravely affect the liver graft with increased mortality and morbidity of LDLT recipients. Therefore, early surveillance for these complications with proper diagnosis and proper management are the key for getting the best possible outcome for graft salvage and patient survival after LDLT.