The effect of graded steatosis on flow in the hepatic parenchymal microcirculation

Background: Steatosis is a major cause of microcirculatory Impairment and graft dysfunction after liver transplantation. The mechanism of this circulatory compromise is unclear. The aim of this study was to evaluate in vivo the effect of steatosis on parenchymal microcirculation and on total hepatic blood flow in an animal model. Methods. Four groups of New Zealand White rabbits (n=24) were investigated. Group 1 were fed on normal diet (controls). In groups 2, 3, and 4 graded steatosis was induced by feeding on a high cholesterol diet (1.5%) for 4, 8, and 12 weeks, respectively. After laparotomy and exposure of the liver, total hepatic blood flow (THBF) and the hepatic parenchymal microcirculation (HPM) were measured. These parameters were correlated with the degree of histological fat infiltration classified as mild (<30%), moderate (30-60%), or severe (>60%). Results. The 4-, 8-, and 12-week cholesterol diets resulted in mild, moderate, and severe steatosis, respectively There was an inverse correlation between the degree of fat infiltration and both HPM (Spearman r=-0.967, P<0.0001) and THBF (r=-0.893, P<0.0001). THBF was 137+/-6 ml/min in controls, which reduced to 121+/-3, 99+/-5, and 63+/-5 ml/min in steatotic Livers of groups 2, 3, and 4, respectively. HPM was 226+/-5 flux units in the controls and 197+/-7, 119+/-8, and 37+/-9 flux units in steatotic livers of groups 2, 3, and 4 respectively. Comparing with controls using analysis of covariance, the fall in HPM and THBF was found to be significant (P<0.002) in the moderate and severe groups, but not significant (P>0.050) in the mild group. Parenchymal perfusion was reduced to a greater extent than total Liver blood flow in moderate and severe grades of steatosis. Conclusions. Fatty infiltration reduces hepatic blood flow and parenchymal microcirculation. The latter is more markedly reduced with severe steatosis. This may explain the development of microcirculatory impairment and graft failure after transplantation of fatty livers despite adequate liver blood flow.