ReviewImaging evaluation of potential donors in living-donor liver transplantation
Introduction
Liver transplantation, introduced by Starzl et al.1 in 1968 is the recognized treatment of choice for patients suffering from end-stage liver disease. Over the years, surgical refinements, greater clinical expertise, and more effective immunosuppression have contributed greatly to the improved technical success of this operation. The growing clinical and political profile of liver transplantation has led to an expansion of the indications for transplantation, and as a consequence an escalating clinical demand for the procedure. Data from the USA, obtained from the United Network for Organ Sharing (UNOS), shows that from January 1 1988 to January 31 2007, a total of 82,157 liver transplants [78,882 (96%) deceased-donor liver, 3275 (4%) living-donor liver] were performed. In 2006 alone there were 6363 deceased and 288 living-donor liver transplants. Despite this, there remains an organ crisis due to a demand and supply imbalance with many more patients requiring liver transplants than there are available. UNOS data shows that a total of 17,429 patients are currently on the waiting list for liver transplantation, and of these patients, 2767 have been waiting for between 1–2 years and 4323 have been waiting 5 years or more. A significant proportion of patients die from their liver disease while on the waiting list. From 1 January 1995 to 31 January 2007, a total of 19,289 people died on the waiting list, while in 2006 alone, there were 1583 deaths.
Out of the need to expand the donor pool (cadaveric supply remaining stable at about 4000 a year) and alleviate this critical organ shortage, the innovative concept of living-donor liver transplantation (LDLT) as a surgical strategy was introduced. Since its inception over a decade ago, it has become a recognized and effective alternative means of liver transplantation for paediatric and adult patients. The number of LDLTs is increasing rapidly, as are the number of transplant centres offering the procedure. There were over four-times more living-donor operations performed in 2006 (288 cases, 4.3% of total liver transplants) than there were 10 years ago in 1996 (62 cases, 1.5% of total liver transplants). Sixty seven centres in the USA had performed at least one LDLT and 24 centres had performed more than 50 cases.
Imaging plays a central role in living-donor programmes by assessing whether potential donors are eligible candidates for donation based on anatomical considerations, and whether co-existing pathology is present. Alongside the evolution of LDLT, developments and refinements in imaging have created techniques that provide robust donor evaluation. In this review, we describe briefly the history of LDLT and discuss in detail the application of imaging in donor assessment with emphasis on use of modern CT and MRI techniques.
Section snippets
History of LDLT
The viability of LDLT as a concept is made possible because of the unique ability of the liver to regenerate following surgery and because its anatomical organization, as defined by Couinaud,2 into independently functioning segments (each with separate vascular inflow and outflow and biliary drainage) favours segmental transplantation. Its introduction as an innovative surgical option grew out of the need to reduce the paediatric waiting list mortality (around 20–30%) by providing appropriate
Hepatic steatosis
Imaging is performed to detect liver parenchymal abnormalities that may preclude living-donor transplantation. Although malignant liver lesions in a potential donor are a contraindication, benign lesions such as haemangioma, particularly if single and small size in size (≤2–3 cm), maybe transplanted safely and do not exclude liver donation.13 However, in the vast majority of cases, parenchymal imaging focuses mainly on detecting hepatic steatosis, which, if present in a significant quantity, can
Vascular anatomy
A comprehensive vascular road map facilitates detailed surgical planning and reduces the postoperative complication rate in both donor and recipient.42, 43 Conventional catheter angiography is the traditional standard of reference for vascular evaluation but has the drawback of being an invasive procedure. Rapid technological advances in cross-sectional imaging have led to non-invasive techniques, such as CT and MRI replacing conventional angiography for routine evaluation of hepatic vascular
Biliary tract anatomy
Anomalous biliary tract anatomy (present in 40% of the population Fig. 6) poses significant technical challenges for LDLT surgery. Postoperative biliary complications (incidence of 15–40% in recipients,56, 57 4–13% in donors58, 59) are the bane of LDLT largely due to the technical difficulties of performing biliary reconstruction on small calibre bile ducts and due to the propensity to severe postoperative bile leakage if even minor intrahepatic branches that cross the dissection line are
“All-in-one” imaging protocols
Donor evaluation is frequently a multi-technique imaging process. This set up is time-consuming and puts substantial demands on radiology resources. To simplify and shorten this diagnostic pathway and make it a more acceptable experience for donors, some centres have explored the possibility of performing donor evaluation as a single comprehensive imaging study.32, 33, 74, 75, 76 CT32, 33 and MRI74, 75, 76 have been assessed for their suitability in providing “all-in-one” imaging – providing
Conclusion
Alongside the evolution of LDLT, developments in imaging have created efficient CT and MR techniques that provide detailed donor evaluation. This facilitates appropriate donor selection and provides crucial preoperative information required for meticulous surgical planning. This process has traditionally involved a multimodality approach, but improvements in CT and MR technology have simplified this pathway into a single comprehensive imaging study (“all-in-one” imaging) that allows
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Cited by (31)
CHAOS Challenge - combined (CT-MR) healthy abdominal organ segmentation
2021, Medical Image AnalysisCitation Excerpt :Precise segmentation is also required to plan liver transplant surgeries. For example, determining whether a portion of the liver to be resected is sufficient for the recipient patient and whether the remaining liver will be sufficient for the donor is an important part of treatment decisions (Low et al., 2008). Furthermore, the determination of the most suitable donors for living donated transplantation and pre-operative planning needs accurate segmentation of the liver.
Contrast-enhanced ultrasonography to evaluate risk factors for short-term and long-term outcomes after liver transplantation: A pilot prospective study
2021, European Journal of RadiologyCitation Excerpt :For example, the Donor Risk Index (DRI) contains the donor covariates of age, cause of death, race, DCD, height, and location [8]; Eurotransplant-DRI contains all the covariates of DRI except race and height and adds the latest serum gamma glutamyl transpeptidase (GGT) and rescue offer [9]; and the UK DCD Risk Score involves age and body mass index (BMI) [10]. In addition, imaging also plays a role in the donor evaluation process, especially in living donor programmes, to provide a preoperative evaluation of the hepatic vasculature, parenchyma, and biliary system [11]. Unlike living donors, DBD and DCD require careful management to ensure that the retrieved organs are in the best possible condition for transplantation.
Liver Transplantation Imaging
2014, Textbook of Gastrointestinal Radiology: Volumes 1-2, Fourth EditionPre-operative hepatic vascular mapping of living donor for liver transplantation using 64-MDCT
2012, Egyptian Journal of Radiology and Nuclear MedicineCitation Excerpt :Special consideration should be paid to accessory hepatic veins draining separately into the IVC, especially if the vein is larger than 3–5 mm and/or the distance between the opening of the confluence of the main hepatic vein into the IVC and the accessory vein is more than 4 cm. In that situation, it would be necessary to modify the surgical planning of anastomosis to prevent unexpected bleeding and drained sector congestion and ischemia. (5,29,33–35). Artioli and colleagues 2010 (20) series of 32 potential liver donors, reported 17 of their cases had accessory right lobe veins draining in inferior cava vein and 15 cases had accessory branches draining in middle hepatic vein crossing dissection line.
Inaccurate preoperative imaging assessment on biliary anatomy not increases biliary complications after living donor liver transplantation
2012, European Journal of RadiologyCitation Excerpt :Since donation hepatectomy is complicated, ensuring the safety of donors is of vital importance, and a thorough and complete preoperative workup including strict evaluation and selection protocols has been advocated [1,2]. Accurate assessment of graft volume and hepatic vascular and biliary anatomy is crucial to reduce the postoperative complications in both donor and recipient [3–6]. Imaging techniques play significant roles in the preoperative assessment and the noninvasive method magnetic resonance cholangiopancreatography (MRCP) enables good visualization of the biliary tree as recently reported [7,8].
Anatomic similarity of the hepatic artery and portal vein according to the donorrecipient relationship
2012, Transplantation ProceedingsCitation Excerpt :Hepatic artery variants are commonly encountered among potential liver donors (up to 45% of the population).1 Several of these variants, such as replaced arteries, are significant because they influence donor suitability and increase surgical complexity.3 In 1966, Michels11 first classified 10 anatomic variations of hepatic artery distribution based on 200 autopsy study cases.12