To meet the need of increasing potential liver transplant recipients, alternative procedures have been developed, such as reduced-size, split and living donor liver transplantation . LDLT has two major advantages over transplantation from a brain-dead donor: excellent graft quality and reduced ischemia-reperfusion injury .
On the other hand, donor safety is the first priority. It is important to keep in mind that LDLT should only be performed if the risk to the donor is justified by expectation of an acceptable outcome in the recipient. Overall donor morbidity is estimated to be approximately 35%, including bile leakage, wound infection and ileus . A recent survey identified 33 living liver donor deaths, including 3 donors who succumbed after an attempted rescue with a liver transplant .
Preoperative imaging of the liver is essential in order to identify and minimize the individual risk of the potential donor. It is further determining for graft survival and in preventing vascular complications. The implementation of imaging studies of the liver, the choice of the imaging modality (CT, MRI, ultrasound, angiography, e.g.) as well as the timing of imaging (early in the evaluation process vs. in the end) varies in different transplant centers.
MRI is undoubtedly becoming more significant in the course of living donor liver evaluation, due to the development of hepatobiliary-specific contrast agents and new imaging techniques (such as chemical shift imaging, MR spectroscopy), opening up new possibilities for comprehensive imaging of the liver [12, 13]. However, availability of MR is still an issue.
The purpose of this retrospective study was therefore to review the radiologist’s contribution to the process of evaluation of donors for LDLT by means of contrast enhanced CT, especially since we can look back on a large group of donors being evaluated with this technique over a significant period of time. Based on the results of the CT scan and liver volumetry in our study 22 candidates were excluded as donors, which accounts for nearly one third (31%) of the cases in which LDLT was not carried out. This relatively high number could be an argument to perform CT imaging early rather than late in the process of donor evaluation. The overall costs for complete donor evaluation have been estimated in previous studies to be in the range from 1383-2569€ , in some centers even as high as 4589€ . Early implementation of CT imaging (estimated costs of approximately 400-600€) in the evaluation process might therefore prevent further studies in unsuitable donors and reduce costs.
Nine candidate donors were excluded because CT indicated steatosis of the liver, which was confirmed with ultrasound and liver biopsy. Fatty infiltration in hepatic grafts is known to be an important risk factor for primary graft nonfunction in deceased donor liver transplantation as well as in LDLT [16, 17]. Liver grafts with a mild degree of fatty changes can be used for liver transplantation without ill effect, but liver grafts with moderate or severe degree of fatty changes have been found to have a negative effect on post transplant graft function and patient survival [17, 18]. Marcos et al estimated that 1% of hepatic steatosis can decrease the functional graft mass by 1% . More recently the same group published a series in which no impairment in function was found in either the living donor or the recipient using grafts containing less than 30% steatosis . In our own institution the acceptable upper limit of fatty changes in the liver graft is 30%.
10 candidate donors were excluded because of the results of liver volumetry, depicting either small (n = 5) or large for size (n = 5) graft volume. Preoperative assessment of total, graft and remnant liver volume is of utmost importance, since inadequate liver mass can influence patient and graft survival. There are several formulas for calculating total liver volume depending on the body weight, body surface and gender [21, 22]. Results do not always correlate and liver volume is often overestimated . Depending on the individual method used, it is considered acceptable when the ratio between graft weight and recipient body weight or between graft volume and the estimated standard liver volume of the recipient are at least 0,8% and 40%, respectively .
In case of left lateral donation remnant liver volume is usually safe for the donor, whereas graft size might be too large in small children. In our study this led to the exclusion of five donors. Especially in case of right liver donation remnant liver volume might be too small (risking acute liver failure of the donor), whereas graft size might as well be too small resulting in a “small-for-size-syndrome” in the recipient, characterized by hepatocyte ballooning, steatosis, centrilobular necrosis and parenchymal cholestasis . This led to the exclusion of three donors who were evaluated for donation of the right lobe.
CT is further important in assessment of vascular hepatic anatomy. Certain anomalies may require modification of the surgical procedure, while others might be a contraindication for surgery . Other vascular variants may even be advantageous, e.g. a displaced right artery arising from the superior mesenteric artery in case of right donation. Due to the greater variability of the right hepatic vascular anatomy right hepatectomy can be one of the most challenging surgical procedures. In addition to the arterial supply of the graft and the remnant liver attention has to be paid to the venous drainage in order to prevent venous congestion. In our study 4 candidate donors were excluded from LDLT because of various vascular anatomic variants. Even though our reported vascular variants do not present absolute contraindications, in these specific cases LDLT would have been involved with an increased surgical complexity and an increased risk of graft failure respectively complications in the donor as well as in the recipient. It is important that anatomic vascular variants are assessed in context with the planned resection, and the decision whether a specific donor is suited for a specific recipient is in the end up to the responsible transplant surgeon.