The extended three-pore model of peritoneal transport

The original three-pore model (TPM) for peritoneal transport was applied according to the theory of the transport through the semipermeable membrane as proposed by Rippe et al.²⁵ and later adapted to the peritoneal dwells with icodextrin-based solutions^2,12,16,17. According to the TPM, fluid flow was considered as dependent on the difference between hydrostatic pressure and osmotic (crystalloid and colloid) pressure exerted by small solutes, icodextrin polymers, and proteins. Diffusive and convective solute transport across peritoneal membrane was considered for small solutes and icodextrin fractions. The absorption of fluid and solutes from the peritoneal cavity was also included in the model. Moreover, our data suggested that to accurately describe the kinetics of icodextrin fractions during peritoneal dialysis, TPM has to be extended by including a description of the degradation of icodextrin polymers due to the α-amylase activity in dialysate, as described in “Results” section. Modelling the dynamics of α-amylase activity is out of the scope of the present study, but we use the data on measured amylase activity to model icodextrin kinetics and to derive information on icodextrin hydrolysis during the peritoneal dwell (see Results).

A detailed description of TPM applied in this study is presented in the ^{Supplementary material} together with the Supplemental Figure ¹ presenting schematic concept of the extended three-pore model (ETPM), whereas in Results detailed description of the extension of TPM is given.