Residual renal function. The recommended dose considers the total renal and peritoneal contribution to clearance. For practical purposes, renal and peritoneal clearances have been considered equivalent. However, recent studies suggest that that is not the case since renal clearance strongly correlates with survival, while peritoneal clearance does not. This is not to say that peritoneal clearance is not important. In fact, studies in anuric patients have shown a clear correlation between survival and dose of PD. It is likely that since renal clearance is associated with many other important physiologic functions, such as volume regulation and hormone synthesis, the favorable effects from these additional benefits, mask the effects of solute removal. The importance of preserving RRF cannot be over-emphasized. See also The Importance of Residual Renal Function.
Body size. Body mass is associated with increased generation of creatinine and urea, and by definition affects normalized clearances. It is logical to expect that patients with more mass will require higher doses of PD.
Peritoneal transport. One of the predominant determinants of small solute clearance is peritoneal transport. The higher peritoneal transport, the higher clearances obtained, all other prescription factors being the same. However, peritoneal glucose absorption is similarly increased and consequently the osmotic gradient diminishes resulting in reduced ultrafiltration in high transport states. Various studies suggest that high peritoneal transport states are associated with a higher risk of death than low and low average transport. See also Prognostic Value of Transport Status.