Effect of haemodialysis on the brain and heart assessed using multiparametric MRI

Haemodialysis (HD) patients often develop cognitive impairment, negatively impacting health-related quality of life. We use brain magnetic resonance imaging (MRI) measures to study the acute changes in cerebral water content during HD, alongside chronic changes in HD patients compared with healthy volunteers (HVs) to assess whether the brain changes associated with ageing develop more rapidly in HD patients ('accelerated brain ageing'). We also study associated cardiac MRI measures.

3T MRI scans were performed during HD in 12 patients to characterize the acute effect of HD on cerebral water content (T1 mapping), alongside previously reported results from the HD-REMODEL (HaemoDialysis interventions to REduce MultiOrgan Dysfunction and Effect on quality of Life assessed by MRI scanning) trial. MRI changes in brain structure [volumes and T1 of white (WM) and grey matter (GM), WM diffusion fractional anisotropy (FA) and mean diffusivity (MD)], perfusion, blood flow, and cardiac measures were compared between HD patients pre-dialysis and HVs (age and gender matched).

WM T1 increased during HD (3.8 ± 1.7%, P = .0005). GM and WM volume [total intracranial volume (TIV)-corrected] were lower in HD compared with HVs [GM volume/TIV: 0.37 (0.34-0.41) vs 0.42 (0.42-0.44), WM volume/TIV: 0.34 ± 0.03 vs 0.37 ± 0.01, P = .009]. In HD, FA was lower and MD higher than HVs (FA: 0.32 ± 0.02 vs 0.35 ± 0.01, MD: 0.59 ± 0.03 vs 0.53 ± 0.01, P < .0001). Higher MD and lower FA was seen in older participants, with steeper slopes in HD (MD: 0.003 vs 0.0006 × 10-3 mm2/s/year P = .003, FA: -0.001 vs -0.0003 units/year P < .0001), suggestive of accelerated ageing. There were no differences between groups in age-related heart changes.

An acute increase in WM T1 during HD has been shown for the first time, reflecting a rise in brain water content. This is potentially caused by the development of an osmotic gradient across the blood-brain barrier due to slower diffusion of urea, and may contribute to acute symptoms and chronic pathological changes contributing to accelerated brain ageing in HD patients.