Renal replacement therapy (RRT) is used to support or replace kidney function (i.e., remove toxins, metabolites, and/or water from the body). RRT is indicated in various acute (e.g., , poisoning, refractory ) and chronic conditions (e.g., ). There are three main RRT modalities: dialysis (either hemodialysis or peritoneal dialysis), hemofiltration, and kidney transplantation. The choice of RRT depends on the anticipated duration of treatment (acute RRT vs. chronic RRT), indications for treatment, patient characteristics, and patient preference. Dialysis uses diffusion to remove solutes from the blood across a semipermeable membrane, while hemofiltration uses convection; both modalities employ varying degrees of ultrafiltration to remove water. Kidney transplantation is the most comprehensive method of RRT in patients with end-stage renal disease (ESRD) and is covered separately in “Transplantation.”
- Acute renal replacement therapy
- Chronic renal replacement therapy
The following is applicable for all patients in whom acute or chronic RRT is being considered.
- Consult nephrology early; optimizing medical management may prevent the need for RRT.
- Stabilize the patient.
- Manage any life-threatening and/or urgent conditions, e.g.:
- Initiate .
- Address .
- Provide .
- Treat any poisoning or overdose (e.g., ).
- Consider diuresis and use fluids judiciously in patients with .
- Manage any life-threatening and/or urgent conditions, e.g.:
- Perform a thorough clinical evaluation, paying particular attention to the following:
- Discontinue and avoid .
- Determine .
- In consultation with nephrology and/or ICU, determine the preferred RRT modality and obtain appropriate access.
Indications for RRT 
- Severe , e.g., pH < 7.1 and/or serum bicarbonate < 12 mmol/L 
- Refractory severe electrolyte abnormalities, e.g., , 
- , particularly uremic pericarditis, uremic encephalopathy, and/or bleeding
- Fluid overload refractory to medical management, e.g., in CKD, CHF
- Poisoning or overdose with a dialyzable substance, e.g., lithium, toxic alcohols
- Additionally, in : 
Dialyzable medications and poisons: “I STUMBLED” - Isoniazid, isopropyl alcohol; Salicylates; Theophylline, Tenormin® (atenolol); Urea; Methanol; Barbiturates; Lithium; Ethylene glycol; Dabigatran, Depakote®(valproic acid)
RRT mechanisms and modalities 
- Solutes move across a semipermeable membrane down their concentration gradient.
- Smaller molecules have faster rates of diffusion and are cleared more easily.
|Comparison of renal replacement therapies |
|Substances removed || || |
|Mechanism || |
|Indications|| || || |
|Disadvantages and complications|| || |
Hemodialysis and hemofiltration
Basic principles 
Hemodialysis: utilizes diffusion and a small degree of ultrafiltration to remove solutes and water from the blood
- More effective at removing small molecules (e.g., urea, creatinine, ammonia) than larger molecules
- Blood is pumped through the dialysis unit on one side of a semipermeable membrane and dialysate in the opposite direction on the other side of the membrane.
- Molecules diffuse across the semipermeable membrane down their concentration gradient.
Hemofiltration: utilizes convection and a high degree of ultrafiltration to remove solutes and water from the blood
- More effective at removing medium to large molecules (e.g., cytokines, myoglobin) than hemodialysis 
- Blood is pumped through a machine and the difference in hydrostatic pressures drives water and solutes across a semipermeable membrane.
- Lost plasma volume is replaced with a physiologic crystalloid solution. 
- Intermittent renal replacement therapy
Continuous renal replacement therapy 
- Gradual fluid and solute clearance over 24 hours
- Used almost exclusively for acute RRT
- Preferred if fluid shifts are contraindicated 
Intermittent RRT can be performed in a clinic or at home by the patient after adequate training.
Venous catheter for renal replacement therapy
- Indications 
- Types of catheter 
- Placement: , preferably in the right internal jugular vein 
- Large bore, double-lumen
- Blood is removed from the vein through one lumen and returned through the other lumen.
Arteriovenous access 
- Indication: for maintenance dialysis in ESRD
- Types of AV access
AV fistulas need approximately 4–6 weeks to mature (i.e., enlargement and thickening of the vein in response to arterial pressure); maturation is unsuccessful in up to 60% of patients. Arrange AV access before dialysis is likely to be required. 
Complications of hemodialysis 
Vascular access complications 
- Loss of access due to thrombosis or stenosis
- Infections e.g., ,
- Local aneurysm
- AV access steal syndrome: painful ischemia of the hand secondary to the AV fistula or graft shunting blood away from the distal limb
Dialysis vascular access hemorrhage 
- Apply firm pressure for 15–20 minutes; avoid occluding the vessel.
- If the patient is hemodynamically unstable:
- Place tourniquets above and below the site and attempt a figure of 8 or purse-string suture.
- Determine time of last dialysis and consider .
- Urgently consult vascular surgery if bleeding is heavy, persists, or recurs.
Cardiovascular complications 
Increased bleeding risk 
- Caused by platelet dysfunction due to CKD and/or platelet contact with the dialysis membrane 
- Avoid systemic anticoagulation solely to maintain or improve hemodialysis catheter patency. 
Dialysis disequilibrium syndrome 
- Definition: the development of acute cerebral edema secondary to the rapid extraction of osmotically active substances (e.g., urea, NaCl) from the blood
- Risk factors 
- Prevention 
- Management: Monitor patients for and initiate if present. 
Other complications 
- Electrolyte abnormalities, e.g., hypophosphatemia
- , which can cause carpal tunnel syndrome 
- Allergic reaction to the equipment or dialysate 
Basic principles 
- Mechanism: utilizes diffusion across the peritoneum (acts as a semipermeable membrane) and ultrafiltration to remove water and solutes from the blood
Administration options: self-administered by highly adherent patients (or their carers) at home 
Continuous ambulatory peritoneal dialysis
- Performed manually 3–5 times/day
- No requirement to be connected to a machine
Automated peritoneal dialysis
- Automated exchange cycles, typically scheduled overnight
- Patients are connected to a machine.
- Continuous ambulatory peritoneal dialysis
- Peritoneal catheter
Because of the high risk of complications, individuals must be trained and able to demonstrate strict adherence to correct techniques before being allowed to perform home peritoneal dialysis. 
Complications of peritoneal dialysis 
- Metabolic disturbances: weight gain, hyperglycemia
- Exit site and catheter tunnel infections
- Protein loss: hypoalbuminemia 
- Abdominal hernias: umbilical and inguinal hernias are most common 
- Leakage of dialysate
- Pleural effusion (rare) 
Frequently examine the peritoneal dialysis catheter and exit site for signs of infection (e.g., swelling, purulent drainage); consider ultrasound for a more detailed assessment if infection is suspected. 
Risk factors 
- Staphylococcus aureus nasal carriage
- Previous exit site infection
- Inadequate peritoneal dialysis training
- Pets in the area where peritoneal dialysis is being performed
- Invasive abdominal procedures (e.g., colonoscopy, cholecystectomy, hysteroscopy)
Clinical features 
- Often asymptomatic and identified by cloudy peritoneal effluent
- may be present.
- Perform a comprehensive clinical evaluation, including an examination of the catheter.
- Obtain a peritoneal fluid sample.
- Systemic signs of infection: Initiate .
- Confirm peritonitis if ≥ 2 of the following are present:
- Admit the patient.
- Initiate systemic antibiotics.  , including empiric
- No systemic signs of infection (common)
- Empiric antibiotic regimens
- Adjust antibiotics based on culture and susceptibility results.
- Start antifungal prophylaxis (oral nystatin or fluconazole). 
- Provide supportive treatment as needed (e.g., pain management, antiemetics).
- Patients with relapsing or refractory peritonitis or confirmed fungal peritonitis: Consider removal of the peritoneal dialysis catheter and temporary hemodialysis. 
- Patient education on peritoneal dialysis catheter care
- Keeping the exit site clean 
- Practicing thorough hand hygiene prior to dialysis exchange
- Prompt treatment of exit site infections
- Addressing modifiable risk factors
Educate patients to monitor effluent characteristics at home and seek medical attention if they observe any changes suggestive of peritonitis (e.g., cloudiness).
Additional management for patients on renal replacement therapy
- Monitor for complications (see “Complications” in “Hemodialysis and hemofiltration” and “Peritoneal dialysis”).
- Avoid nephrotoxic medications and adjust medications accordingly. 
- Involve a renal dietitian in management.
- Coordinate necessary vaccinations with the treating nephrologist. 
- Preserve active and future vascular access sites. 
- Do not use blood pressure cuffs on extremities with active RRT access.
- Avoid forearm venipunctures.
- Coordinate any nonemergent line placement with nephrology.
- Avoid unnecessary blood transfusions in patients awaiting kidney transplantation. 
- Discuss with patients on dialysis. 
Contact nephrology and/or a pharmacist for all medication dosing and if clinical management may affect or be affected by RRT.
Do not access any RRT lines except in an emergency, if no other access is available.