Peritoneal Dialysis

Peritoneal dialysis uses the patient's own peritoneal membrane as the dialyzing surface. Dialysate instilled into the peritoneal cavity through a permanent catheter draws solutes across the peritoneal capillaries by diffusion and removes fluid by osmosis driven by an osmotic agent such as glucose. It is a predominantly home-based modality, performed either as continuous ambulatory exchanges by hand or as automated cycling overnight.

Definition

Peritoneal dialysis is a renal replacement technique in which dialysate is instilled into the peritoneal cavity so that solutes diffuse across the peritoneal membrane and water is removed by osmotic ultrafiltration, with the dialysate periodically drained and replaced.

Scope

This topic covers the physiology of peritoneal solute and water transport, the principal techniques (continuous ambulatory and automated peritoneal dialysis), the concept of adequacy in this modality, and peritonitis as its defining complication. It is a reference description of the modality and its evidence base, not clinical guidance.

Core questions

• How does the peritoneal membrane act as a dialyzer?
• What distinguishes continuous ambulatory from automated peritoneal dialysis?
• How is adequacy assessed in peritoneal dialysis?
• Why is peritonitis the central complication of this modality?

Key concepts

• Peritoneal membrane as dialyzing surface
• Osmotic ultrafiltration with glucose-based dialysate
• Continuous ambulatory peritoneal dialysis (CAPD)
• Automated peritoneal dialysis (APD)
• Dwell time and exchange cycles
• Peritoneal equilibration and membrane transport status
• Peritonitis

Mechanisms

Dialysate dwelling in the peritoneal cavity exchanges solutes with blood in the peritoneal capillaries across the peritoneal membrane: waste solutes diffuse into the dialysate down their gradients while an osmotic agent (commonly glucose) generates the gradient that pulls plasma water across, producing ultrafiltration. Clearance depends on dwell time, exchange volume, and the individual membrane's transport characteristics. Adequacy in this modality has been studied in terms of combined peritoneal and residual kidney clearance and its association with outcomes (CANUSA, 1996). Because the system breaches the peritoneal cavity through an indwelling catheter, bacterial peritonitis is the characteristic infectious complication, and its prevention and treatment are the subject of dedicated international recommendations (Li et al., 2022).

Clinical relevance

Peritoneal dialysis is an established home-based alternative to in-centre hemodialysis, and understanding its principles supports interpreting modality comparisons and the literature on its outcomes and complications. This entry describes the modality and its evidence; it is not guidance for selecting or managing dialysis in an individual.

Epidemiology

Peritoneal dialysis accounts for a substantial minority of dialysis worldwide, with uptake varying widely between health systems. Peritonitis is the most important modality-specific complication and a leading reason for technique failure and transfer to hemodialysis (Li et al., 2022).

Evidence & guidelines

The CANUSA study examined associations between peritoneal dialysis adequacy, nutrition, and clinical outcomes and shaped later thinking about residual kidney function (CANUSA, 1996). The International Society for Peritoneal Dialysis publishes regularly updated peritonitis recommendations (Li et al., 2022). Registry comparisons of dialysis and transplantation provide context for modality and outcome discussions (Wolfe et al., 1999).

History

Peritoneal dialysis became a practical chronic therapy after the development of a permanent indwelling peritoneal catheter in the 1960s, and continuous ambulatory peritoneal dialysis was introduced in the late 1970s, allowing home-based treatment without a machine. Automated cycling devices later extended the modality. Adequacy and peritonitis prevention have been progressively codified, including through the CANUSA study and successive ISPD recommendations.

Debates

How should adequacy targets weigh residual kidney function?

Reanalysis of adequacy data highlighted that residual kidney clearance contributed substantially to the outcomes originally attributed to total small-solute clearance, prompting debate over how peritoneal dialysis prescriptions and targets should account for residual function.

Key figures

• Henry Tenckhoff
• Karl Nolph
• Philip Kam-Tao Li

Seminal works

• canusa-1996
• li-2022-ispd

Frequently asked questions

How is peritoneal dialysis different from hemodialysis?

Peritoneal dialysis uses the body's own peritoneal membrane and instilled dialysate inside the abdomen, usually performed at home, whereas hemodialysis circulates blood through an external artificial membrane, typically in a dialysis centre.

What is the main complication of peritoneal dialysis?

Peritonitis — infection of the peritoneal cavity — is the characteristic complication, a major cause of technique failure and the focus of dedicated international prevention and treatment recommendations.