Renal Replacement Therapy and Dialysis

Renal replacement therapy (RRT) is the set of treatments that substitute for the excretory and homeostatic functions of failed kidneys. It comprises hemodialysis, peritoneal dialysis, the related continuous therapies used in critical illness, and kidney transplantation, which is the only modality that restores endocrine and metabolic kidney function rather than substituting for filtration alone.

Definition

Renal replacement therapy denotes any modality — dialysis or transplantation — that takes over the excretory, fluid-balance, acid-base, and electrolyte functions of kidneys that have failed acutely or chronically.

Scope

This area orients the reader across the major modalities used when kidney function is inadequate to sustain life: blood-based dialysis (hemodialysis), the peritoneum-based alternative (peritoneal dialysis), the vascular and catheter access that dialysis requires, kidney transplantation with its immunosuppression, and the long-term complications shared across modalities. It frames these as a reference taxonomy of clinical concepts, not as treatment guidance.

Sub-topics

• Complications of Long-Term Dialysis
• Hemodialysis Principles and Dose
• Kidney Transplantation and Immunosuppression
• Peritoneal Dialysis
• Vascular Access for Hemodialysis

Core questions

• What distinguishes the dialysis modalities from one another and from transplantation?
• How is the dose or adequacy of dialysis conceptualised and why does it matter?
• Why is transplantation associated with survival and quality-of-life advantages over long-term dialysis in suitable candidates?
• What complications are common to all forms of long-term renal replacement therapy?

Key concepts

• Renal replacement therapy (RRT)
• Diffusion and convection as solute transport mechanisms
• Dialysis dose and adequacy
• Modality selection (hemodialysis, peritoneal dialysis, transplantation)
• Vascular and peritoneal access
• Transplant survival benefit
• Cardiovascular burden of chronic kidney failure

Mechanisms

Dialysis modalities clear solutes and water by physical principles: diffusion across a semipermeable membrane down concentration gradients, convection (solvent drag) during ultrafiltration, and osmosis, depending on the technique. Hemodialysis circulates blood across an artificial membrane; peritoneal dialysis uses the patient's own peritoneal membrane and instilled dialysate. Continuous therapies apply the same principles more slowly for unstable patients. Transplantation differs fundamentally by restoring a living nephron mass and the kidney's endocrine functions, at the cost of lifelong immunosuppression to prevent rejection. The notion of adequacy — quantified historically through measures such as Kt/V — formalises how much small-solute clearance a treatment delivers (Gotch & Sargent, 1985; Eknoyan et al., 2002).

Clinical relevance

Renal replacement therapy sustains people with kidney failure and is central to nephrology practice; understanding its modalities supports reading the evidence on outcomes such as survival and cardiovascular risk. Observational data associate transplantation with lower mortality than remaining on the waiting list in suitable candidates (Wolfe et al., 1999). This entry describes how these therapies are categorised and studied and is not a basis for individual modality selection or treatment decisions.

Epidemiology

Kidney failure requiring replacement therapy is a major contributor to chronic-disease burden worldwide, and cardiovascular disease is the leading cause of death among people on dialysis (Foley et al., 1998). Modality availability and the balance between in-centre hemodialysis, home therapies, and transplantation vary substantially across health systems.

Evidence & guidelines

Landmark randomised and cohort evidence anchors the field: the HEMO trial examined dialysis dose and membrane flux in maintenance hemodialysis (Eknoyan et al., 2002), and large registry-based analyses described the survival comparison between dialysis and transplantation (Wolfe et al., 1999). Modality-specific guidance is summarised in the topic entries.

History

Practical chronic dialysis became possible in the mid-twentieth century, building on Willem Kolff's wartime artificial kidney and Belding Scribner's arteriovenous shunt that enabled repeated vascular access. Peritoneal dialysis and, decisively, kidney transplantation followed, transforming kidney failure from a uniformly fatal condition into a chronically managed one. Subsequent decades refined dialysis dosing, access, and immunosuppression.

Key figures

• Belding Scribner
• Willem Kolff
• Garabed Eknoyan
• Robert Wolfe

Seminal works

• eknoyan-2002-hemo
• wolfe-1999

Frequently asked questions

What are the main types of renal replacement therapy?

The principal modalities are hemodialysis, peritoneal dialysis, continuous renal replacement therapies used in critical care, and kidney transplantation. Dialysis substitutes for filtration; transplantation restores a functioning kidney including its endocrine roles.

Why is transplantation often discussed as the preferred long-term option?

Cohort evidence associates kidney transplantation with lower long-term mortality and better quality of life than maintenance dialysis in suitable candidates, though it requires surgery and lifelong immunosuppression. This is a descriptive observation, not individual advice.