Peritoneal Dialysis

ProcedureTop

In peritoneal dialysis (PD), low- and medium-molecular-weight solutes, uremic toxins, and water move across the peritoneum (the counterpart of a dialysis membrane in an artificial kidney)—a serous membrane that separates the rich vascular environment beneath the peritoneal mesothelium—from the osmotically charged electrolytic dialysate cyclically infused to and removed from the peritoneal cavity.

Kinetics

During peritoneal dialysis, 3 transport processes occur simultaneously: diffusion, ultrafiltration, and absorption. The transport of solutes across the peritoneal membrane is mainly based on diffusion, which depends on the concentration gradient between sides of the peritoneum and on the molecular weight of the waste solute. Dialysis efficiency is positively correlated with the concentration gradient and negatively correlated with the membrane thickness and size of diffusing molecules. Water is removed through osmotic ultrafiltration (UF) provided by high glucose concentration in standard dialysate solutions. Alternative dialysates contain icodextrin, a glucose polymer that ensures sustained UF during long exchanges. Regulation of electrolyte balance is ensured through diffusion, particularly of potassium, magnesium, and calcium. UF plays an important role in sodium balance; however, in clinical practice water clearance does not always correlate with sodium removal (particularly in patients undergoing dialysis treatment using icodextrin). Acid-base balancing is achieved through the use of either standard dialysis solutions containing lactates that are metabolized to bicarbonates or alternative solutions containing bicarbonates. Peritoneal fluid absorption occurs via the lymphatics at a relatively constant rate, with typical values of 0.2 to 0.4 mL/min.

Technique

Access to the peritoneal cavity is obtained through a peritoneal catheter (see below), which is used to infuse the dialysate and remove the dialysis effluent. A PD set consists of a peritoneal catheter, transfer set, dialysate bag, waste products/dialysis effluent bag with draining tubes, and, in the case of automated peritoneal dialysis (APD), also a device (cycler) that does the automated PD exchanges.

Types of PD:

1) Continuous ambulatory peritoneal dialysis (CAPD): Three to 5 exchanges per 24 hours are performed by the patient or another person manually (without cycler use).

2) Nocturnal intermittent peritoneal dialysis (NIPD): APD performed at night (3-5 cycles) with no fluid in the peritoneal cavity during the day (no last fill).

3) Continuous cycling peritoneal dialysis (CCPD): APD at night plus a last fill of the dialysate, which remains in the peritoneal cavity during the day.

4) Urgent-start PD: Initiation of PD within 2 weeks of catheter insertion. The starting PD prescription is adjusted to minimize the risk of pericatheter leaks (eg, supine APD, low volumes of 1-1.5 L, day dry).

PD is a home-based therapy, performed by the patient and/or their caregiver after training completion. In some geographic areas with adequate community resources, assisting nurses may be available to provide PD in the patient’s home or at a long-term care facility, for those who are not able to perform PD alone due to social, cognitive, or physical barriers. The patient remains in constant contact with the treatment monitoring center. Some APD machines have remote monitoring capabilities. PD is associated with longer survival in the initial 2 to 3 years of the therapy and good quality of life; and patients may be able to continue education/work. In many countries, PD is less costly than hemodialysis (HD).

In patients with preserved residual kidney function, PD can be started using an incremental approach (incremental PD), in which the dialysis dose is gradually increased when residual kidney function declines, in order to maintain the desired values of total solute clearance (both renal and peritoneal). This is achieved by increasing the volume and/or duration as well as the number of exchanges per 24 hours. Incremental PD (up to 2 exchanges/24 h in CAPD and up to 5 sessions/wk in APD) ensures preservation of residual kidney function for the average of 12 months.

Implantation of Peritoneal Dialysis Catheters

A silicone double-cuff Tenckhoff catheter with a straight or curled tip and perforated intraperitoneal segment is commonly used. A peritoneal catheter can be inserted surgically, using an open surgery or laparoscopy. Laparoscopy allows for precise placement of the catheter with short recovery time and lower risk of leaking at the insertion site. A nonsurgical approach using ultrasound and/or fluoroscopic guidance is also used by interventional radiologists and nephrologists.

Proper implantation, use, and maintenance of the PD catheter as well as proper diagnosis and treatment of catheter-related complications (see below) are needed to ensure lasting PD catheter function. The type of PD catheter does not affect the incidence of PD-related peritonitis. Antibiotic prophylaxis prior to catheter insertion (eg, cefazolin, vancomycin) reduces the incidence of infectious complications. Full-volume dialysis is usually initiated 2 weeks following catheter implantation.

Dialysates

Proper selection of dialysate component concentration and modification of the dialysate dwell time are the key methods to affect/optimize the dialysis process. The commonly used dialysates have improved biocompatibility to ensure longer peritoneum suitability as the dialysis membrane. These include fluids in multichamber bags, with neutral pH and low content of glucose degradation products, as well as bicarbonate-buffered solutions (rather than lactate-buffered ones). The glucose contained in the dialysates (at various concentrations) acts as an osmotic agent that ensures UF (fluid removal) in patients. The icodextrin-containing dialysate (icodextrin is a starch-derived glucose polymer) used in nocturnal CAPD or diurnal CCPD is effective at managing volume status and does not cause negative metabolic effects resulting from glucose absorption. It is indicated especially in patients with diabetes mellitus and rapid transperitoneal transport in the peritoneal equilibration test (PET), although its beneficial effect on patient survival has not been proven. Dialysates with low sodium content, favoring sodium removal and ensuring better blood pressure control, are also available.

Assessment of Adequacy of Peritoneal Dialysis

1) Clinical criteria: Absence of uremic symptoms.

2) Adequate dialysis dose expressed as:

a) Weekly creatinine clearance (for patients on APD) ≥45 L/1.73 m2.

b) Weekly urea clearance expressed as Kt/V ≥1.7, where K, urea clearance (mL/min or L/h); t, length of the dialysis treatment (min or h); V, urea distribution volume (mL or L).

Currently PD adequacy is assessed in a broader perspective, particularly when treating patients with comorbidities and short life expectancy. High-quality dialysis involves setting realistic therapeutic goals by the patient and the health care personnel, which would allow the patient to pursue their own goals and priorities, including those related to their physical, mental, and social well-being. In this way, the health care team may implement and continue patient-centered treatment.

IndicationsTop

1. Acute kidney injury (AKI): PD may be considered in patients with AKI if there are urgent indications to initiate dialysis treatment (see Renal Replacement Therapy) and extracorporeal methods of RRT are unavailable or contraindicated. However, delays in timely access to PD catheter insertion in many hospitals limits the use of PD in patients with AKI.

PD is the method of choice in children with AKI. It is also used in countries with limited access to extracorporeal methods. PD treatment is usually initiated immediately after catheter insertion and involves low volume and short dwells (1-2 h), with frequent exchanges of bicarbonate-buffered dialysate and varying glucose concentrations depending on the desired UF rate.

2. End-stage renal disease (ESRD): The maintenance PD regimen is a type of RRT that can be used as an alternative to HD in patients with ESRD. According to the concept of integrated kidney care, it should be considered a first-line dialysis modality, particularly in those with preserved residual kidney function. PD is thought to be suitable also in older adults and in patients with diabetes, obesity, polycystic kidney disease, cirrhosis, following uncomplicated surgeries within the peritoneal cavity, and after kidney allograft failure.

3. Additional factors favoring the use of PD:

1) Psychosocial reasons:

a) Need for a more liberal daily timetable, for instance, in those with active professional or personal life.

b) Place of residence at a considerable distance from the HD center and good housing standard.

2) Lack or nonfeasibility of vascular access needed for HD, for instance, in children.

3) Hemodynamic instability during HD sessions.

4) Minimization of pandemic infection risk through much less frequent contacts with other patients and health care personnel compared with facility IHD.

ContraindicationsTop

Absolute contraindications to PD include unsuitable peritoneum due to the risk of dialysis membrane failure (eg, history of peritoneal fibrosis, adhesions, peritoneal cancer) and/or high risk for peritonitis (eg, active inflammatory bowel disease, active abdominal infections), unsuitable home environment (eg, housing insecurity, unclean conditions, or vermin infestation), inadequate ability (cognitive or physical) to perform PD by the patient or their caregiver.

ComplicationsTop

Infectious Complications of Maintenance Peritoneal Dialysis

1. Catheter-related infections: Exit-site infections (ESIs) or tunnel infections (TIs) increase the risk of PD-related peritonitis and account for ~40% of lost peritoneal access. ESI is diagnosed in the presence of purulent discharge with or without skin erythema. The most common etiologic agents are Staphylococcus aureus and Pseudomonas aeruginosa. ESI prevention includes good hand hygiene and exit-site care including the use of daily topical antibiotics such as mupirocin.

2. PD-related peritonitis: The diagnosis is made when ≥2 of the following are present:

1) Clinical features such as abdominal pain and/or cloudy dialysis effluent.

2) Dialysis effluent white blood cell count >100/microL or >0.1 x109/L, with >50% polymorphonuclear leukocytes (PMNs) on the differential.

3) Positive dialysis effluent culture.

The most common cause is a break in technique during the process of connecting or disconnecting the PD set. Less frequently, PD-related peritonitis is disseminated by continuity in those with concomitant ESI/TI. PD-related peritonitis can also be caused by diarrhea or constipation (bacterial translocation across the intestinal wall), diagnostic procedures without previous antibiotic prophylaxis (colonoscopy, hysteroscopy), appendicitis, or colonic diverticulitis. The most common etiologic agents are gram-positive bacteria (55%-80%, including coagulase-negative staphylococci and S aureus), Enterococcus spp and Streptococcus spp (up to 15%), gram-negative bacteria (up to 30%), and fungi (up to 15%). Initial broad-spectrum antibiotics for the treatment of PD-related peritonitis can be given intraperitoneally. The choice of empiric antibiotics should consider local antibiotic susceptibility and resistance patterns. Antibiotic treatment is modified after 48 hours, depending on the dialysis effluent culture result, with subsequent clinical and laboratory evaluation performed after 4 to 5 days of targeted treatment. A PMN count in the dialysis effluent ≥1090/microL on day 3 or 4 of treatment is an independent predictor for treatment failure. Noneffective targeted antibiotic therapy is an indication for PD catheter removal (Table 1). Treatment duration in PD-related peritonitis depends on the etiologic agent: 14 days for culture-negative or gram-positive bacteria (other than those specified below); and 21 days for P aeruginosa, other gram-negative bacteria, Enterococcus spp, and S aureus. In fungal infections treatment involves catheter removal and use of antifungal agents for 4 to 6 weeks. Of note, polymicrobial growth on culture should prompt investigation into secondary peritonitis of other etiologies (eg, secondary to appendicitis, perforation of intestinal diverticulum, or acute pancreatitis). PD technique retraining should occur following peritonitis and/or catheter infections. Antifungal prophylaxis (eg, oral nystatin or oral fluconazole) is recommended when treating bacterial PD-related peritonitis.

Noninfectious Complications of Maintenance Peritoneal Dialysis

1. Hyponatremia: About 15% of patients undergoing CAPD or APD have permanent hyponatremia. Management includes modification of diet, fluid intake, and UF. Hyponatremia is observed in patients undergoing PD with icodextrin-containing solutions; it has no impact on clinical management.

2. Inadequate UF can be defined clinically as failure to achieve euvolemia despite the use of ≥3 hypertonic exchanges per day (objectively, UF failure is defined as <400 mL UF following a 4-h exchange with a 4.25% glucose dialysate).

Mechanical causes of decreased UF should be excluded in radiographic imaging, to ascertain placement of the peritoneal catheter, or in computed tomography (CT) of the abdominal cavity. Additionally, a PET should be performed to evaluate the transport of low-molecular-weight solutes (creatinine, glucose) across the peritoneal membrane. If a person is classified as a high transporter based on PET (ie, has rapid transport through the peritoneal membrane), the CAPD regimen should be modified by introducing one long exchange with icodextrin or APD should be used instead of CAPD. Icodextrin is only slightly absorbed, which ensures a sustained UF effect. In patients with preserved residual kidney function, the use of diuretics may result in increased water removal due to increased urine output. Patients with UF failure caused by intraperitoneal fibrosis, encapsulating peritoneal sclerosis (EPS), or a history of severe PD-related peritonitis may develop uremic symptoms along with volume overload, which is treated by switching to HD. Risk factors for EPS include long PD treatment duration (>5 years), use of glucose-rich, low-pH solutions, high content of glucose degradation products in the dialysate, and frequent episodes of PD-related peritonitis, particularly caused by P aeruginosa or S aureus. EPS is a chronic clinical syndrome with undernourishment accompanied by persistent or recurrent intestinal obstruction with or without inflammatory parameters. The diagnosis is verified by peritoneal thickening, sclerosis, calcifications, and encapsulation confirmed by macroscopic inspection or radiologic findings. EPS is an indication to switch the patient to HD.

3. Complications related to increased intra-abdominal pressure:

1) Abdominal hernias develop in 10% to 15% of patients treated for >5 years.

2) Dialysate leakage to the abdominal wall, pleural cavity, and genitals may occur.

3) Mechanical impairment of pulmonary ventilation.

4) Delayed gastric emptying.

5) Gastroesophageal reflux.

6) Sacral and lumbar pain.

DiscontinuationTop

Indications for dialysis modality switch from PD to HD:

1) PD-related peritonitis: In some situations it may be indicated to remove the PD catheter and temporarily or permanently switch the patient to HD (Table 1).

2) Inadequate dialysis (uremic symptoms) or UF failure.

3) Patient’s or caregiver’s inability to perform the PD on their own and unavailability of assisted PD.

3) Failure of the peritoneal membrane as a result of peritoneal fibrosis or development of EPS.

Tables