Exploring the Effects of Hemodialysis on Renal and Hepatic Blood Flow and Function using CT Perfusion Imaging
Abstract
Hemodialysis (HD) is the most common form of renal replacement therapy for end-stage renal disease. However, patients develop complications that are driven by HD-induced circulatory stress from rapidly removing large fluid volumes during HD, making various vascular beds vulnerable to ischemia. By assessing how HD-induced circulatory stress affects different organs, it may be possible to characterize the mechanisms behind these complications and evaluate therapeutic interventions. This thesis aims to explore how HD affects renal and hepatic blood flow and function using CT perfusion imaging. For this work, patients received either standard or cooled HD first in a two-visit, crossover study design, where imaging was performed before, during and after each HD session.
Residual renal function is linked to improved clinical outcomes, yet characteristically declines upon HD initiation. In the first thesis project, we determined that renal perfusion deceases during HD, which could be an early manifestation of HD-mediated residual renal function loss.
Although the liver normally clears endotoxin, increased circulating endotoxin levels have been found in HD patients. In the second thesis project, we showed that concurrent hepatic perfusion redistribution and decreased liver function during HD are likely responsible for increased circulating toxin levels.
Dialysate cooling is a low-cost, feasible intervention that ameliorates HD-induced circulatory stress. In the first and second thesis projects, we found that cooling trended towards mitigating the drop in renal perfusion during HD and ameliorating the changes in liver perfusion and function during HD.
If it were possible to accurately assess glomerular filtration rate (GFR) in HD patients, HD prescriptions could be adjusted in accordance with residual renal function to preserve remaining function. In the third thesis project, we extended the CT perfusion technique to measure GFR in HD patients, yielding physiologically realistic GFR values, thus demonstrating the feasibility of this approach in terms of reliability and accuracy.
These findings help explain residual renal function loss and endotoxemia in HD patients, and showcases the protective potential of dialysate cooling. In addition, this work demonstrates the benefit of using CT perfusion as a functional imaging technique to further characterize and evaluate therapies for end-stage renal disease pathologies.