Ultrafiltration and free water transport during the peritoneal equilibration test: Clinical relevance of the association with intraperitoneal pressure

Background Intraperitoneal pressure (IPP) may influence ultrafiltration (UF) in peritoneal dialysis (PD), but its clinical relevance under standard peritoneal equilibration test (PET) with 4.25%/3.86% dextrose remains uncertain. Methods In 96 unselected PD patients, we performed two 4.25%/3.86% PETs using 1L and 2L fill volumes. IPP, UF, glucose UF efficiency, sodium dip (Na-Dip) as a marker of free water transport (FWT), osmotic conductance to glucose (OCG), and solute transport parameters (D/P Creatinine and diffusion capacities (PS)) were assessed. Associations between IPP, UF parameters, and UF-related abnormalities were analyzed. Results The 2L PET showed higher IPP, dialysate glucose concentration, and PS, and lower D/P Creatinine , as expected. However, an increase in water transport was not consistent: 21%, 66%, 29%, and 40% of patients showed in the 1L PET, respectively, higher UF, glucose UF efficiency, OCG, and Na-Dip. In 2L PET IPP was negatively correlated with UF ( r = −0.221; p = 0.03) and Na-Dip ( r = −0.210, p = 0.041). About 56% of patients presented at least one of the UF-related abnormalities identified (paradoxically higher UF with 1L, UF insufficiency (UF < 400 mL in 2L PET), and impaired FWT (Na-Dip≤5 mmol/L in 2L PET)). These patients had significantly higher IPP and reduced abdominal distensibility. Conclusions This study shows an association between IPP and UF in 4.25%/3.86% dextrose PET that appears clinically relevant. It also raises the hypothesis that IPP may be related to FWT in PD. These findings highlight the importance of IPP monitoring in PD and the need for further studies to characterize changes in FWT across variations in volume and intraperitoneal pressure.