Renal volume-pressure and functional relationships in acute allograft rejection

This study was undertaken to determine the mechanical basis for renal swelling in unmodified renal allograft rejection and to explore further the relationship between parenchymal swelling and renal function. From each of 17 pairs of mongrel dogs, matched for weight, a donor and recipient animal were chosen. Ten of the pairs were studied by microsphere (MS) techniques to examine the relationship between cortical zonal swelling and cortical zonal blood flow. In the other seven pairs of dogs, we estimated the distending pressure of the allograft on day 6 post-transplant by measurement of renal subcapsular pressure (RSCP) and wedge renal venous pressure (WRVP). This was done to assess whether the renal swelling was related to changes in intrarenal pressure or to changes in renal compliance. In all studies serum creatinine concentration (SCr) was measured on the day of transplant, day 2, and day 6 post-transplantation. We found that RSCP and WRVP were not increased in the swollen allograft. In addition, we found that the increase in SCr was significantly correlated with the degree of allograft swelling (r = 0.57, P < 0.05). However, significant increases in SCr were not observed until renal volume was greater than twice normal. Finally, we found that outer and inner cortical zonal blood flows were negatively correlated with the degree of cortical zonal swelling (r = −0.57), P < 0.05). We conclude that renal allograft swelling is principally the result of a profound increase in renal compliance (a profound decrease in renal tissue cohesive forces), and the degree of glomerular filtration rate (GFR) and cortical blood flow impairment are correlated with the degree of renal swelling. These findings suggest that the compliance-mediated swelling of acute renal injury may adversely affect renal function.