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HDF Middle Molecule Clearance CONVINCE — ESENeph MCQ

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ModerateHaemodialysisHDF Middle Molecule Clearance CONVINCEESENeph

A 62-year-old man with CKD G5D on haemodialysis has been well dialysed (spKt/V 1.6) but has persistent fatigue, poor concentration, and generalised malaise. His Hb is 115 g/L, PTH is within KDIGO target, and dialysate composition is standard. He recently switched from thrice-weekly high-flux HD to thrice-weekly haemodiafiltration (HDF). After 3 months on HDF, his symptoms improve significantly. What is the most likely explanation for his improvement?

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Correct answer: E — Enhanced middle molecule clearance, particularly beta-2-microglobulin

Haemodiafiltration combines diffusion (haemodialysis) with convection (high-volume ultrafiltration with replacement fluid), providing superior clearance of middle molecules (500-60,000 Da) compared to conventional HD. Key middle molecules include beta-2-microglobulin, p-cresyl sulphate, indoxyl sulphate, and complement factors. The CONVINCE trial (2023) demonstrated reduced all-cause mortality with high-dose HDF (convection volume ≥23 L/session) compared to high-flux HD. Middle molecule accumulation contributes to uraemic symptoms (fatigue, pruritus, neuropathy, inflammation) that persist despite adequate small solute clearance (adequate Kt/V). This explains why symptom improvement can occur despite unchanged Kt/V.

Reference: Blankestijn et al 2023 – CONVINCE Trial; UKKA 2023 – HDF Position Statement