Peritoneal blood capillary endothelial over mesothelial surface area in individuals with normal kidney function, and in children with CKD5 and on PD. Age-dependent variation in the ratio of the human parietal peritoneal mesothelial surface area relative to the blood microvessel endothelial surface area in individuals with normal kidney function, ANOVA P = 0.0003 (A) and in children with CKD5 and on PD, ANOVA P < 0.0001 (B). Dashed line represents equal mesothelial/peritoneal and blood microvessel endothelial surface area (ratio = 1). MSA = mesothelial surface area, BESA = blood microvessel endothelial surface area, PSA = peritoneal surface area.