Liver transplantation in rats using small-for-size grafts: a study of hemodynamic and morphological changes

Graft injury in relation to graft size in right lobe live donor liver transplantation: a study of hepatic sinusoidal injury in correlation with portal hemodynamics and intragraft gene expression

OBJECTIVE

To investigate the degree and mechanism of hepatic sinusoidal injury in different graft sizes in right lobe live donor liver transplantation (LDLT).

SUMMARY BACKGROUND DATA

Liver grafts from living donors are likely to be small-for-size for adult recipients. Graft injury after reperfusion is common, but the mechanism and degree of injury remain unclear. The hepatic sinusoidal injury in different graft sizes and its relationship with portal hemodynamics and intragraft gene response at the early phase after reperfusion have not been studied in right lobe LDLT.

METHODS

From May 2000 to November 2001, 40 adults receiving right lobe LDLT had portal pressure measured continuously before and after reperfusion. Liver biopsies were taken before and after reperfusion for detection of vasoregulatory genes (endothelin-1 and endothelial nitric oxide synthase) and heat shock genes (heat shock protein 70 and heme oxygenase-1), and electron microscope examination. Blood samples from the portal vein and suprahepatic inferior vena cava were taken for the measurement of plasma nitric oxide level.

RESULTS

The recipients were grouped according to the ratio of graft weight to estimated standard liver weight: group 1 (n = 10), less than 40%; group 2 (n = 21), 40% to 60%; and group 3 (n = 9), more than 60%. The portal pressures recorded after reperfusion in group 1 were significantly higher within 30 minutes of reperfusion than those in groups 2 and 3. After reperfusion, the intragraft endothelin-1 mRNA level in group 1 increased by 161% of the basal level but decreased by 31.5% and 62% of the basal level in groups 2 and 3, respectively. The intragraft mRNA level of heme oxygenase-1 in groups 1 and 2 decreased by 75.5% and 25.3% of the basal level respectively but increased by 41% of basal level in group 3. The intragraft protein level of heat shock protein 70 decreased by 50 ng/mL after reperfusion in group 1 but increased by 12.4 ng/mL and 0.6 ng/mL in groups 2 and 3, respectively. The portal vein plasma nitric oxide level decreased more significantly after reperfusion in group 1 than in group 2. Electron microscope examination of liver biopsies in group 1 showed tremendous mitochondrial swelling as well as irregular large gaps between the sinusoidal lining cells. There were two hospital deaths in group 1 and none in the other two groups.

CONCLUSIONS

Patients implanted with grafts less than 40% of standard liver weight suffered from transient portal hypertension early after reperfusion. The phenomenon was accompanied by intragraft upregulation of endothelin-1 and ultrastructural evidence of sinusoidal damage. The transient portal hypertension after reperfusion, subsequent endothelin-1 overexpression, and plasma nitric oxide level reduction, together with downregulation of heme oxygenase-1 and heat shock protein 70, may account for the small-for-size graft injury.

Hemodynamic interaction between portal vein and hepatic artery flow in small-for-size split liver transplantation

In split-liver transplantation, the entire portal flow is redirected through relatively small-for-size grafts. It has been postulated that excessive portal blood flow leads to graft injury. In order to elucidate the mechanisms of this injury, we studied the hemodynamic interactions between portal vein- and hepatic artery flow in an experimental model in pigs. Six whole pig liver grafts were implanted in Group 1 ( n=6) and six whole liver grafts were split into right and left grafts and transplanted to Groups 2 ( n=6) and 3 ( n=6), respectively. The graft-to-recipient liver volume ratio was 1:1, 2:3 and 1:3 in Groups 1, 2 and 3, respectively. Portal vein- and hepatic artery flows were measured with an ultrasonic flow meter at 60,120 and 180 min after graft reperfusion. Portal vein pressure was also recorded at the same time intervals. Graft function was assessed at 3,6h and 12h, and morphological changes at 12h after reperfusion. Following reperfusion, portal vein flow showed an inverse relationship to graft size, while hepatic artery flow was reduced proportionately to graft size. The difference was significant among the three groups ( P<0.05). Portal vein pressure was significantly higher in group 3, compared to groups 1 and 2 ( P<0.05). Hepatic artery buffer response was significantly higher in Group 3, compared to Groups 1 and 2 in relation to pre-occlusion values ( P<0.05). Split-liver transplantation, when resulting in small-for-size grafts, is associated with portal hypertension, diminished arterial flow, and graft dysfunction. Arterial flow impairment appears to be related to increased portal vein flow.

Small-for-size partial liver graft in an adult recipient; a new transplant technique

We report a new technique of adult liver transplantation using a small-for-size graft. In order to avoid graft congestion and failure by overperfusion, we completely diverted the superior mesenteric venous flow by a mesocaval shunt with downstream ligation of the superior mesenteric vein. The recipient recovered well, and the graft had normal histology and function at 5 months follow-up. Given the current scarcity of cadaveric donors, this technique may increase the numbers of adult recipients by using left lobes from cadaveric split liver grafts.