On this page

Peritoneal dialysis (PD): overview

AKA: automated peritoneal dialysis (APD)/continuous cycler peritoneal dialysis (CCPD), continuous ambulatory peritoneal dialysis (CAPD), continuous optimized peritoneal dialysis (COPD), intermittent peritoneal dialysis (IPD), nightly intermittent peritoneal dialysis (NIPD), tidal peritoneal dialysis (TPD)

A general overview of the principles of peritoneal dialysis therapy in pediatric patients


  • Sterile dialysate fluid is introduced into the peritoneal cavity via a catheter and exchanged at intervals
    • Typically, the dialysate is infused, allowed to dwell for a period of time, and then drained; this cycle is repeated a number of times
      • Exception: continuous flow peritoneal dialysis
  • Rather than using an extracorporeal dialyzer/filter, the patient’s peritoneal membrane serves as the semipermeable membrane
    • The presence of small pores aquaporin channels allow water to move through the membrane.
    • The peritoneum is highly vascular and the presence of capillaries allows for transfer of solutes.

Peritoneal membrane as filter

Why it works

  • Within the peritoneal membrane (between the abdominal wall and the peritoneal cavity) there are capillaries, lymphatic vessels, and interstitial spaces
    • These enable the absorption of particles from the dialysate (in the peritoneal cavity) into the rest of the body
    • The peritoneal capillaries enable the movement of water (by
      ) into the peritoneal cavity
  • Transport in PD is an interaction of diffusion,
    , and fluid absorption

Peritoneal transport: “three pore” conceptual model

  • Large pores (>20 nm [>200 Å] diameter)
    • <10% of the pores in the peritoneal membrane
    • Permit transport of proteins (e.g., immunoglobulins) and other large molecules
    • Can be increased with significant inflammation such as peritonitis
  • Small pores (4-6 nm [40-60 Å] diameter)
    • ~90% of pores in the peritoneal membrane
    • Transport most small molecules
  • Ultra small pores (0.3-0.5 nm [3-5 Å] aquaporins)
    • 1-2% of pores in the peritoneal membrane
    • Responsible for nearly half of water transport

Diffusion in PD: key factors

  • Concentration gradient of solute: dialysate/plasma (D/P) ratio
  • Mass transfer area coefficient (MTAC)
    • Effective peritoneal surface area (analogous to the K0A in
      • Surface area of the peritoneal membrane
      • Vascularity: how many peritoneal capillaries are in the peritoneum
    • Diffusive characteristics of membrane for solute in question (permeability)
      • Varies from patient to patient
      • Changes in individuals over time
  • Particle size:
    • Small molecules diffuse rapidly
    • Large molecules take a longer time to diffuse across the peritoneal membrane

Ultrafiltration in PD: key factors

  • Osmotic gradient: fluid removal (
    ) is accomplished using osmotic pressure rather than hydrostatic pressure
    • The osmotic gradient is created by including an osmotic agent (e.g., dextrose, icodextrin) in the dialysate
      • Increasing the concentration of the osmotic agent generates a greater osmotic gradient and results in more fluid removal
      • Using dialysate with higher dextrose concentration generates a greater osmotic gradient and results in more fluid removal
  • Reflection coefficient: how resistant a particle in the dialysate is to being absorbed (i.e., how well it stays in the dialysate), on a scale of 0 to 1
    • An osmotic agent with a reflection coefficient of 1 would be an ideal osmotic agent: it would draw water into the peritoneal cavity without being absorbed
  • Ultrafiltration coefficient (of the membrane): depends on the surface area and the number of pores
  • Hydrostatic pressure
    • Filling the peritoneal cavity with dialysate increases the hydrostatic pressure
  • Oncotic pressure gradients
    • Related to changes of protein levels inside the bloodstream as water is removed from the peritoneal cavities

Fluid absorption

  • Peritoneal fluid, including dialysate, is absorbed during peritoneal dialysis:
    • Direct lymphatic absorption
    • Tissue absorption (into the interstitium) of peritoneal fluid
  • Fluid absorption limits
    and mass transfer
    • Higher levels of peritoneal absorption reduces the net

Comparison with HD

  • PD is generally the preferred chronic dialysis modality in pediatrics
    • Depends on patient and family preference, institutional practice and availability

Advantages of PD

  • Vascular access is not required
  • Better outcomes (vs
    ) in the US
    • Gentler fluid removal over longer time period avoids cardiac stunning seen in
    • Better preservation of remaining kidney function
    • Better outcomes after kidney transplantation
    • Better growth
    • Improved fluid balance
      • Also reduces need for antihypertensive medications
  • Daily clearance
    • Less accumulation of toxins (e.g., phosphorus, potassium) between sessions
  • Better quality of life
    • Home treatment (less frequent travel to the dialysis unit)
    • Self control of the therapy
    • No needles
    • Facilitates school attendance/employment
    • Extended travel is possible
    • Fewer dietary restrictions
  • Less technically difficult, especially in babies
    • Teaching usually takes 3-5 days

Disadvantages of PD

  • Risk of infection: peritonitis, exit site, and tunnel infections
  • Hernias
  • Decreased appetite
  • Body image disturbance
  • Labor intensive
  • Drawbacks of home PD:
    • Caregiver burden
    • Requires a lot of physical space to keep supplies
    • Requires a savvy family
      • However, even with poor educational background (e.g., illiteracy) can be trained to be competent

Contraindications to PD

  • Anatomical
    • Multiple prior abdominal surgeries with lots of scarring
    • Compromised diaphragm with communication between abdominal and thoracic cavities (e.g., diaphragmatic hernia, surgical complication)
    • Other congenital abnormalities: omphalocele, gastroschisis, bladder exstrophy
  • ≥2 prior episodes of peritonitis
  • Obliterated peritoneal cavity
    • E.g., from prior surgeries, trauma, infections
  • Peritoneal membrane failure

Relative contraindications

  • Presence of ileostomies/colostomies
    • Ideally would locate as far away as possible from the PD exit site to avoid contamination
  • Infants with significant organomegaly
  • Impending abdominal surgery
  • If expecting transplant soon (typically <3-6 months), usually prefer to initiate
    • Significant time investment of planning surgery, waiting for tract to mature, training of patient/family
  • Lack of appropriate caregiver(s)
  • Lack of appropriate home environment