Patients on chronic peritoneal dialysis (PD) (including both continuous ambulatory peritoneal dialysis [CAPD] and automated forms of peritoneal dialysis [APD] such as continuous cycler peritoneal dialysis [CCPD]) occasionally have difficulty achieving solute removal goals or maintaining euvolemia. Both inadequate solute removal and volume overload have multiple etiologies.
This topic reviews factors that contribute to inadequate solute removal among PD patients and discusses the clearance of particular solutes. This topic also reviews volume overload among PD patients, and provides an approach to evaluating such patients.
The factors that regulate solute and water transport across the peritoneal membrane are discussed separately. (See "Mechanisms of solute clearance and ultrafiltration in peritoneal dialysis".)
The following discussion assumes that the peritoneal dialysis prescription was initially adequate and that solute clearance and/or fluid removal have become impaired over time. A review of the factors that must be considered at the initiation of dialysis is presented separately. (See "Choosing a modality for chronic peritoneal dialysis".)
Among peritoneal dialysis patients, total solute removal or clearance consists of the removal of the solute in question by both dialysis and residual renal clearance. The clearance of a particular solute is often used as a measure of the dialysis dose; in such cases the term clearance refers to the amount of blood that is “cleared” of a substance over a unit of time. The dialysis dose or clearance may also be expressed by normalizing it to the particular solute’s volume of distribution that the solute was cleared from such as Kt/V.