Modifying liver blood flow in liver transplant recipients

The portal vein carries 75 percent of the blood flow to the liver, with the remainder flowing through the hepatic artery. If blood flow through the portal vein is too high, the hepatic artery becomes constricted and blood flow through it decreases. This leads to damage to the liver and surrounding tissues. In liver donation recipients, increased portal blood flow can lead to graft failure; failure of small grafts in particular has been attributed to excess portal blood flow.

Several investigators have demonstrated that portal flow modulation (reducing blood flow through the portal vein) can improve outcomes in living donor liver transplantation recipients. In the Adult-to-Adult Living Donor Liver Transplantation Cohort Study (A2ALL), investigators expanded on this research by performing a multi-center observational study of the effect of portal flow modulation on graft outcomes in the setting of increasing use of smaller and left lobe grafts.

In a sample of 274 living donor liver transplant recipients, a total of 57 portal flow modulations were performed in 52 patients. After modulation, hepatic arterial flow increased in about half of patients, and portal vein flow decreased in 61 percent of patients. The most consistent changes were observed in portal vein pressure; all but three patients had unchanged or lower portal vein pressure after modulation.

A higher percentage of patients in the modulation group experienced graft dysfunction compared to patients without flow modulation (31 percent compared to 18 percent). Yet this did not result in an increase in graft loss for the modulation group; survival at two years after transplant was 90 percent for modulated patients and 81 percent for unmodulated patients.

The next steps for this research question should be to implement cohort study testing using a defined protocol for portal flow modulation in small grafts to define the best approach for modulation and to clarify the impact of blood flow in the liver at small graft sizes. 

CITATION:Emond JC, Goodrich NP, Pomposelli JJ, Baker TB, Humar A, Grant DR, Abt P, Friese CE, Fisher RA, Kam I, Sherker AH, Gillespie BW, Merion RM. Hepatic hemodynamics and portal flow modulation: The A2ALL experience. Transplantation. 2017 In press.
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