Peritoneal dialysis uses the peritoneum as a natural permeable membrane through which water and solutes can equilibrate. Compared to hemodialysis, peritoneal dialysis is
Less physiologically stressful
Does not require vascular access
Can be done at home
Allows patients much greater flexibility
(See also Overview of Renal Replacement Therapy.)
However, peritoneal dialysis requires much more patient involvement than in-center hemodialysis. Maintaining sterile technique is important. Of the total estimated resting splanchnic blood flow of 1200 mL/minute, only about 70 mL/minute comes into contact with the peritoneum, so solute equilibration occurs much more slowly than in hemodialysis. But because solute and water clearance is a function of contact time and peritoneal dialysis is done nearly continuously, efficacy in terms of solute removal is equivalent to that obtained with hemodialysis.
In general, dialysate is instilled through a catheter into the peritoneal space, is left to dwell, and then drained. In the double-bag technique, the patient drains the fluid instilled in the abdomen in one bag and then infuses fluid from the other bag into the peritoneal cavity.
Peritoneal dialysis can be done manually or using an automated device.
Manual methods include the following:
Continuous ambulatory peritoneal dialysis (CAPD) does not require a machine to do the exchanges. A typical adult infuses 2 to 3 L (children, 30 to 40 mL/kg) of dialysate 4 to 5 times a day. Dialysate is allowed to remain for 4 hours during the day and 8 to 12 hours at night. The solution is manually drained. Flushing the infusion set before filling reduces peritonitis rates.
Intermittent peritoneal dialysis (IPD) is simple, and useful chiefly in the treatment of acute kidney injury (AKI). In adults, 2 to 3 L (in children, 30 to 40 mL/kg) of dialysate, warmed to 37° C, is infused over 10 to 15 minutes, allowed to dwell in the peritoneal cavity for 30 to 40 minutes, and drained in about 10 to 15 minutes. Multiple exchanges may be needed over 12 to 48 hours. This method of dialysis was historically used 3 times a week in a hospital or an outpatient dialysis unit setting, but has fallen out of favor due to concerns about inadequate small solute clearances, and the development of more efficient automated peritoneal dialysis techniques.
Automated peritoneal dialysis (APD) is becoming the most popular form of peritoneal dialysis. It uses an automated device to do multiple nighttime exchanges, sometimes with a daytime dwell. There are 3 types:
Continuous cyclic peritoneal dialysis (CCPD) uses a long (12 to 15 hours) daytime dwell and 3 to 6 nighttime exchanges done with an automated cycler.
Nocturnal intermittent peritoneal dialysis (NIPD) involves nighttime exchanges and leaves the patient's peritoneal cavity without dialysate during the day.
Tidal peritoneal dialysis (TPD) involves leaving some dialysate fluid (often more than half) in the peritoneum from one exchange to the next, resulting in greater patient comfort and avoiding the problems (eg, frequent repositioning) resulting from inability to completely drain dialysate. TPD may be done with or without a daytime dwell.
Some patients require both CAPD and CCPD to achieve adequate clearances.
Access
Peritoneal dialysis requires intraperitoneal access, usually via a soft silicone rubber or porous polyurethane catheter. The catheter may be implanted in the operating room under direct visualization or at the bedside by blind insertion of a trocar or under visualization through a peritoneoscope. Most catheters incorporate a polyester fabric cuff that allows tissue ingrowth from the skin or preperitoneal fascia, ideally resulting in a watertight, bacteria-impervious seal and preventing introduction of organisms along the catheter tract. Allowing 10 to 14 days between catheter implantation and use improves healing and reduces the frequency of early pericatheter leakage of dialysate. Double-cuff catheters are better than single-cuff catheters. Also, a caudally directed exit site (the opening of the tunnel through which the catheter enters the peritoneal cavity) lowers the incidence of exit-site infections (eg, by collecting less water during showering).
Once access is established, the patient undergoes a peritoneal equilibration test, in which dialysate drained after a 4-hour dwell time is analyzed and compared with serum to determine solute clearance rates. This procedure helps determine the patient’s peritoneal transport characteristics, the dose of dialysis required, and the most appropriate technique. In general, adequacy is defined as a weekly Kt/V ≥
Complications of Peritoneal Dialysis
The most important and common complications of peritoneal dialysis (see table Complications of Renal Replacement Therapy) are
Peritonitis
Catheter tunnel exit-site infection
Peritonitis
Peritonitis symptoms and signs include abdominal pain, cloudy peritoneal fluid, fever, nausea, and tenderness to palpation.
Diagnosis of peritonitis is made by clinical criteria and testing. A sample of peritoneal fluid is obtained for Gram stain, culture, and white blood cell (WBC) count with differential. Peritonitis is present if a patient has at least 2 of the following criteria:
Clinical features consistent with peritonitis (eg, abdominal pain, tenderness, and/or cloudy dialysis effluent)
Dialysis effluent WBC > 100/mcL with > 50% polymorphonuclear cells after a dwell time of at least 2 hours
Positive peritoneal fluid culture (1)
Gram stain is often unrevealing, but cultures are positive in > 90%. About 90% also have > 100 WBCs/mcL, usually neutrophils (lymphocytes with fungal peritonitis). Negative cultures and WBC counts < 100/mcL do not exclude peritonitis, so treatment is indicated if peritonitis is suspected based on clinical or laboratory criteria and should begin immediately, before culture results are available. Peritoneal fluid studies may be falsely negative due to prior antibiotic use, infection limited to the catheter exit site or tunnel, or sampling of too little fluid.
Pearls & Pitfalls
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Most cases of peritonitis respond to prompt antibiotic therapy. If peritonitis does not respond to antibiotics within 5 days or is caused by recurrence of the same organism or by fungi, the dialysis catheter is removed.
Catheter tunnel exit-site infection
Complications reference
1. Li PK-T, Chow KM, Cho Y, et al: ISPD (International Society of Peritoneal Dialysis) peritonitis guideline recommendations: 2022 Update on prevention and treatment. Perit Dial Int 42(2):110-153, 2022. doi: 10.1177/08968608221080586
Prognosis for Peritoneal Dialysis
Overall, 5-year survival rate in peritoneal dialysis patients is slightly better than that of hemodialysis patients (about 47% in peritoneal dialysis compared to 42% in hemodialysis).
