Peritoneal dialysis (PD) uses the capillary network in the peritoneal membrane to achieve water and solute transport and is described via the 3-pore model.1 Most abundant are small pores (40-60 Å), accounting for over 95% of solute removal. A lesser number of large pores (100-200 Å), formed by interendothelial cell clefts, serve as sites of macromolecule transport. Ultrasmall pores (2.5 Å) were identified as aquaporin 1 channels (AQP-1) facilitating electrolyte-free water transport across the peritoneal membrane.