Expanded Hemodialysis Versus High-Volume Online Hemodiafiltration for Uremic Toxin Removal

Expanded hemodialysis (HDx) using medium cut-off (MCO) membranes has been developed to improve the removal of medium-sized uremic toxins while maintaining effective clearance of small solutes. These medium-sized molecules have been associated with inflammation, cardiovascular disease, and other complications in patients with end-stage kidney disease. High-volume online hemodiafiltration (HV-OL-HDF) is currently considered a reference therapy for enhanced removal of these toxins, but its use may be limited by technical requirements, vascular access constraints, or resource availability.

While expanded hemodialysis has shown removal efficiency comparable to high-volume hemodiafiltration in prior studies, the optimal prescription of HDx-particularly the appropriate treatment duration-has not been clearly established. In routine clinical practice, dialysis dose is commonly guided by small-solute clearance (such as urea), which may not fully reflect the removal of medium-sized uremic toxins. A more comprehensive evaluation of toxin removal may help optimize dialysis prescriptions and improve treatment personalization.

This study is designed to compare the efficiency of uremic toxin removal across different expanded hemodialysis treatment durations and to contrast these results with high-volume online hemodiafiltration. Removal efficiency will be assessed using the Global Removal Score, a composite measure that integrates the removal rates of several small and medium-sized molecules while accounting for albumin loss.

The study is a single-center, randomized, open-label, crossover trial conducted in adult patients receiving maintenance hemodialysis. Each participant will receive three expanded hemodialysis sessions with different treatment durations (180, 210, and 240 minutes), administered in randomized sequences following the long interdialytic interval. After completion of the three expanded hemodialysis sessions, all participants will undergo one session of high-volume online hemodiafiltration with a predefined convective volume target.

During each study session, blood samples will be collected immediately before and after dialysis to measure concentrations of selected uremic toxins, including small solutes and medium-sized molecules. These measurements will be used to calculate individual and global removal rates for each dialysis modality and treatment duration. Standard dialysis parameters will be maintained according to institutional practice to ensure patient safety and consistency across sessions.

The crossover design allows each participant to serve as their own control, reducing variability related to patient-specific factors. The primary analysis will compare global toxin removal between expanded hemodialysis prescriptions and high-volume online hemodiafiltration, as well as across different HDx treatment durations.

The findings of this study may help clarify whether expanded hemodialysis with shorter or standard treatment times can achieve toxin removal comparable to high-volume hemodiafiltration. This information could support more individualized dialysis prescriptions and inform clinical decision-making in settings where high-volume hemodiafiltration is not feasible or routinely available.

Inclusion criteria

• Adults aged 18 years or older
• End stage renal disease Receiving maintenance hemodialysis three times per week on expanded hemodialysis as part of routine care for at least 1 month
• On dialysis treatment for more than 3 months
• Minimal or no residual urine output (less than 100 mL per day)
• Able and willing to provide written informed consent

Exclusion criteria

• Vascular access unable to support a blood flow of at least 300 mL/min