Determinants of low clearances of small solutes during peritoneal dialysis

Peritoneal dialysis plasma clearances of large molecular weight solutes such as inulin (5,200 daltons) usually equal or exceed plasma clearances of such solutes seen with extracorporeal dialyzers, [1–4]. Clearances of smaller solutes such as urea (60 daltons), however, are usually 15% or less of urea clearances with extracorporeal dialysis systems. In Table 1, typical values for clearances of urea and inulin, dialysis solution flow rate (QD), blood flow rate (QB), and surface area are compared for peritoneal and extracorporeal (hemodialysis) techniques. Effective peritoneal capillary blood flow rate is unknown. Gross total anatomical peritoneal surface area is estimated to be approximately equal to body surface area [2, 4]