THE NECESSITY OF PROVIDING VENOUS DRAINAGE FOR THE RIGHT ANTERIOR SECTOR OF SMALL-FOR-SIZE RIGHT LOBE GRAFT IN LIVING-DONOR RIGHT LOBE LIVER TRANSPLANTATION:

P506 Aim: In cases of living-donor liver transplantation (LDLT) using right lobe grafts, the possibility of venous outflow problems associated with deprivation of the middle hepatic vein (MHV) tributaries should be taken into account. It is likely that small-for-size right lobe grafts are susceptible to graft dysfunction caused by outflow disturbance. This study was performed to determine the necessity of providing venous drainage for the right anterior sector of small-for-size right lobe graft in LDLT by use of intraoperative near-infrared spectroscopy (NIRS). Methods: Twenty-five patients undergoing right lobe LDLT were enrolled in this study. During the course of harvesting and implantation, NIRS measurements were performed on both the anterior and posterior segments of the liver grafts to determine hemoglobin (Hb) and cytochromeoxidase (Cyt.aa3) contents in the hepatic tissues. Results: The 25 cases were divided into three groups according to the caliber of the major MHV tributaries in the grafts: small (<4mm) group (n=7), intermediate (4-7mm) group (n=9), and large (>7mm) group (n=7). After implantation, congestion, i.e., increase in tissue Hb content, was observed in both the segments regardless of the caliber of the MHV tributaries. However, the congestion in the anterior segment was severer than that in the posterior segment in the intermediate and large groups. No significant changes in oxidized Cyt.aa3 were seen in either of the segments in the small and intermediate groups, indicating well-preserved mitochondrial redox state. In order to estimate the significance of venous collaterals in a right lobe graft before implantation, NIRS was also performed on the anterior segment of the right lobe graft to quantify tissue content of Hb during initial ex vivo perfusion. In most cases, tissue content of Hb was rapidly decreased by flushing. However, Hb content in the anterior segment remained high even after flushing in some cases in the large group, demonstrating poor venous collaterals. The extent of postoperative congestion in the anterior segment was significantly correlated with the tissue content of remaining Hb in that segment after flushing (R2=0.77). The intermediate group included 5 recipients of small-for-size right lobe graft (graft-to-recipient body weight ratio < 0.8, ranging from 0.68 to 0.8). The recipients of small-for-size graft showed significantly lower AKBR and higher blood NH3 levels after LDLT than the recipients of larger graft did. In two of the five small-for-size grafts, over 30% of Hb remained in the anterior segment after flushing. In the recipients of those congestive small-for-size grafts, the normalization of AKBR and NH3 levels were markedly delayed. Conclusions: NIRS enables quantification of the extent of congestion in the anterior segment after implantation of a right lobe liver graft and even enables prediction of such congestion at the phase of ex vivo perfusion. Reconstruction of the MHV tributaries might be required in cases of small-for-size graft with the congestive anterior segment.