NEW research presented at UK Kidney Week 2026 suggests that convection volume in haemodiafiltration (HDF) could be tailored to individual patients rather than applying a universal high-volume approach.
The Role of Middle-Molecule Clearance in Dialysis Outcomes
HDF has been associated with improved survival compared with high-flux haemodialysis (HD), with enhanced removal of middle molecules, such as β2-microglobulin (β2M), thought to contribute to this benefit. However, large randomised trials comparing HDF with HD have not consistently shown reductions in pre-dialysis β2M levels in HDF-treated patients. One possible explanation is that these studies did not account for residual kidney function (RKF), which is known to influence both β2M concentrations and patient survival.
Researchers from Lister Hospital and the University of Hertfordshire therefore investigated the relationship between HDF convection volume, RKF, and β2M clearance. Current HDF practice generally aims for a high convection volume of around 23 L per session, regardless of individual kidney function. The researchers hypothesised that understanding the relative contributions of dialysis and RKF to β2M clearance could help individualise HDF prescriptions.
The team analysed 220 patients receiving maintenance haemodialysis with post-dilution HDF for more than four weeks. During a monitored dialysis session, convection volume was recorded and pre- and post-dialysis β2M levels were measured. RKF was assessed using interdialytic urine collection. Using these data, the researchers developed a two-pool β2M kinetic model to estimate β2M removal during dialysis and over a week via renal, non-renal, diffusive, and convective pathways.
Multivariable linear regression identified convection volume, glomerular filtration rate (GFR), and body weight as significant predictors of both sessional and weekly β2M removal (p<0.001; R²=0.6). The contribution of HDF to β2M removal increased as GFR declined and body weight increased, reaching its highest levels in anuric patients weighing more than 80 kg.
Importantly, the difference in weekly β2M removal between high (≥23 L) and low (<23 L) convection volumes was statistically significant only in anuric patients (1225 mg vs 1015 mg; p<0.001).
Towards Individualised Haemodiafiltration Prescriptions
The findings suggest that high convection volumes may be most beneficial for larger patients without residual kidney function. In contrast, smaller patients with preserved RKF may achieve adequate middle-molecule clearance with lower convection volumes or even conventional high-flux HD.
According to the authors, these results support a more individualised approach to dialysis prescribing, potentially starting with high-flux HD and transitioning to high-volume HDF as residual kidney function declines.
Reference
Butt U et al. Can haemodiafiltration convection volume be individualised? UKKW, 10-12 March, 2026.
Featured image: Kiryl Lis on Adobe Stock
