acute peritoneal dialysis definition procedure apparatus pros and cons

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acute peritoneal dialysis definition procedure apparatus advantages disadvantages

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Acute Peritoneal Dialysis

Definition

Peritoneal dialysis (PD) is a renal replacement therapy that uses the peritoneal membrane - the serous, semipermeable lining of the abdominal cavity - as a natural dialysis filter. Cleansing fluid (dialysate) is instilled into the peritoneal cavity via a catheter, where it absorbs waste products, excess electrolytes, and fluid from the peritoneal blood vessels by diffusion and osmosis. The spent fluid is then drained and discarded.

Acute peritoneal dialysis (APD) specifically refers to PD used for acute kidney injury (AKI) rather than end-stage kidney disease. It is an attractive modality for AKI because it is as effective as hemodialysis, requires far less infrastructure, and can be performed with solutions and catheters adapted to local resources - making it especially valuable in low-resource settings.

Brenner and Rector's The Kidney, p. 3233

Physiological Basis

The peritoneal membrane functions on a three-pore model:

Large pores (>150 Å) - transport proteins and large solutes
Small pores (40-45 Å) - main route for small solute exchange (urea, creatinine, electrolytes)
Ultra-small pores / aquaporins (2-5 Å) - water-only transport (free water removal)

The adult peritoneum has a surface area of 1.6-2.0 m², but microvilli increase total functional surface area up to 40 m². Solute transfer occurs by:

Diffusion - down concentration gradients from blood into dialysate
Convection (ultrafiltration) - water and solutes dragged across by osmotic pressure from dextrose in dialysate
Osmosis - free water movement through aquaporins
Brenner and Rector's The Kidney, p. 2094-2095

Apparatus and Access

1. Peritoneal Catheter (Primary Access)

The catheter is the cornerstone of PD. The most widely used is the Tenckhoff catheter, made of silicone rubber or polyurethane.

Component	Details
Intraperitoneal portion	Straight, coiled, Ash (T-Fluted), or with silicone disc
Extraperitoneal portion	Straight or swan-neck design
Cuffs	Single or double Dacron cuffs; most common = double cuff, swan-neck, coiled Tenckhoff
Placement	Placed between visceral and parietal peritoneum near the pouch of Douglas

Placement techniques:

Blind (Seldinger) technique
Surgical (open) placement
Peritoneoscopic approach
Laparoscopic placement
Moncrief-Popovich technique
Fluoroscopic ± real-time ultrasound guidance

The coiled catheter decreases pain during infusion and reduces migration risk. The swan-neck design reduces cuff extrusion and exit-site infection. The inner cuff is placed in the rectus muscle to prevent leaks; the outer cuff sits in subcutaneous tissue to prevent infection migration.

For acute/urgent PD, low-volume PD can begin within 24 hours of catheter placement if no other dialysis access is available; typically PD starts 2-4 weeks after placement to allow wound healing.

Brenner and Rector's The Kidney, p. 2914; Campbell-Walsh Wein Urology, p. 2914

2. Dialysate Solutions

Component	Details
Osmotic agent	Dextrose (glucose) at 1.5%, 2.5%, or 4.25%; or icodextrin (glucose polymer)
Buffer	Lactate (conventional) or bicarbonate (biocompatible solutions)
Electrolytes	Na⁺, K⁺, Ca²⁺, Mg²⁺ in physiologic concentrations
pH	Conventional: acidic (pH ~5.5); biocompatible: physiologic pH (neutral)

1.5% dextrose - least ultrafiltration, used for maintenance
2.5% dextrose - moderate ultrafiltration
4.25% dextrose - maximum ultrafiltration, used for fluid-overloaded patients; more glucose absorption and hyperglycemia risk
Icodextrin - a glucose polymer minimally absorbed; maintains osmotic gradient for up to 18 hours in long dwells; color-coded commercially (yellow = 1.5%, green = 2.5%, red = 4.25%)
Washington Manual of Medical Therapeutics, p. 505

3. Cycler (Automated PD Machine)

In automated PD, a cycler machine performs preprogrammed exchanges overnight while the patient sleeps. It controls inflow volume, dwell time, and drainage automatically.

Procedure

Phases of Each PD Exchange ("Dwell Cycle")

Fill (Infusion) - Dialysate flows by gravity or pump into the peritoneal cavity (typically 2-3 L for adults; 1.25-1.5 L/m² body surface area)
Dwell - Fluid dwells in the peritoneum; diffusion and osmosis occur across the membrane (duration varies by modality)
Drain - Used dialysate drains out by gravity via the catheter and is discarded

Key Prescription Variables

Dwell volume (2-3 L typical)
Dwell time
Number of exchanges per day
Dextrose concentration

Modalities

1. Continuous Ambulatory PD (CAPD) - Manual

Patient manually performs 3-5 exchanges per day
Each exchange takes 30-40 minutes
Fluid dwells continuously; no machine required
Overnight long dwell with slow equilibration
Works at home, work, or while traveling

2. Automated PD (APD) / Continuous Cycling PD (CCPD)

A cycler machine runs multiple exchanges overnight (typically 8-10 hours)
A final fill remains in the peritoneum during the daytime
Frees the patient from daytime exchanges
Preferred for patients working during the day

3. Tidal PD (a variant of APD)

A portion of dialysate always remains in the peritoneum ("tidal volume"), reducing pain from repeated complete drainage

4. Intermittent PD (IPD) - used for acute setting

Exchanges performed periodically (e.g., several hours per day, not continuous)
Traditional approach for acute PD in hospitalized patients

Feature	APD	CAPD
Cost	Higher ($$$$)	Lower ($$)
Mechanical complications (hernia, leaks)	Lower risk (dry day option)	Higher risk
Catheter complications	Drain pain, alarms	Easier for "fussy" catheters
Assisted PD (elderly)	Easier (1-2 nurse visits/day)	More challenging
Cirrhosis/ascites	More challenging	Can control drain volume
Urgent start	Lower leak risk	Higher mechanical complications

National Kidney Foundation Primer, p. 611

Advantages of Acute PD

Clinical:

Effective solute and fluid removal - comparable to hemodialysis for AKI
Continuous therapy, more closely mimicking natural kidney function
Gradual fluid removal reduces hemodynamic instability (better tolerated in hypotensive patients)
Preserves residual kidney function longer than hemodialysis
Needle-free - no vascular access needed
Fewer dietary restrictions (less inter-dialytic build-up of K⁺, Na⁺, fluid)
Reduced cardiovascular stress (no rapid extracorporeal fluid shifts)

Practical:

Requires far less infrastructure than hemodialysis - suitable for low-resource settings
Can use locally manufactured/adapted solutions and catheters
No need for anticoagulation (unlike hemodialysis with extracorporeal circuits)
Can be performed at home by patients or caregivers
Allows travel; supplies shipped directly
Can dialyze while sleeping (APD)
Can be started within 24 hours in urgent AKI if no other access available
Brenner and Rector's The Kidney, p. 3233

Disadvantages and Complications of Acute PD

Infectious Complications

Complication	Details
Peritonitis	Most serious; up to 6% mortality per episode. Diagnosed by: cloudy effluent + dialysate WBC >100/µL (>50% neutrophils) + positive culture. Treat with intraperitoneal antibiotics (vancomycin or 1st-gen cephalosporin + 3rd-gen cephalosporin or aminoglycoside)
Exit-site infection	Erythema, tenderness, purulent drainage at catheter exit
Tunnel infection	Infection along subcutaneous catheter track

Non-Infectious Complications

Hernia formation - due to increased intra-abdominal pressure from fluid dwell
Dialysate leaks - especially with early catheter use
Back pain - from increased intra-abdominal pressure
Catheter migration / obstruction - outflow failure requiring repositioning
Hydrothorax - dialysate leaking into pleural space through diaphragmatic defects
Hyperglycemia - from glucose absorption, especially with high-dextrose solutions
Weight gain / abdominal distension - from glucose absorption
Protein loss - significant protein lost in dialysate, contributing to malnutrition
Ultrafiltration failure - especially in high peritoneal transporters on long-dwell regimens

Modality Limitations

Less efficient per session than conventional intermittent hemodialysis (compensated by continuous nature)
Must be performed daily (7 days/week) - schedule burden
Requires strict sterile technique training and patient compliance
Large patients may need extra therapy volume
Requires home storage space for supplies and machine
Some healthcare providers less familiar with PD than HD, leading to under-referral
Contraindicated or difficult in: recent abdominal surgery, extensive adhesions, active abdominal infection (relative), large body habitus, respiratory failure (intolerance of raised intra-abdominal pressure), severe malnutrition with very low serum albumin
Washington Manual of Medical Therapeutics, p. 505-506; Brenner and Rector's The Kidney

Special Considerations: Acute PD in AKI and Low-Resource Settings

Acute PD is particularly valued in resource-limited settings (Africa, Asia, parts of South America) because:

HD requires electricity, treated water, trained staff, and expensive machines
PD can be done with minimal equipment and locally adapted materials
The "Saving Young Lives" initiative specifically promotes sustainable acute PD programs in very low-resource settings, particularly for children with AKI
It has been used successfully in COVID-19 AKI when CRRT machines were overwhelmed, though it was sometimes difficult in the most critically ill patients requiring prone positioning
Brenner and Rector's The Kidney, p. 3233, 3982

Summary Table: Acute PD at a Glance

Aspect	Details
Definition	Peritoneal membrane used as dialysis filter in AKI
Access	Tenckhoff catheter (double cuff, swan-neck, coiled)
Dialysate	Dextrose 1.5/2.5/4.25% or icodextrin; lactate or bicarbonate buffer
Exchange phases	Fill → Dwell → Drain
Modalities	Intermittent PD (IPD), CAPD, APD/CCPD
Key advantage	Low infrastructure, continuous, hemodynamically gentle
Key risk	Peritonitis (6% mortality/episode), ultrafiltration failure

diagram

Generating Image

Detailed medical diagram of acute peritoneal dialysis showing: a cross-section of the human abdomen with the peritoneal cavity, a Tenckhoff catheter inserted through the abdominal wall with its internal coiled tip near the pouch of Douglas, the three phases of dialysis labeled with arrows - Phase 1 Fill (dialysate flowing in from a dialysate bag above), Phase 2 Dwell (fluid inside peritoneal cavity with arrows showing diffusion of urea, creatinine, potassium, and water from peritoneal blood vessels into dialysate), Phase 3 Drain (spent dialysate draining out into a collection bag below). Include a close-up inset showing the three-pore model of the peritoneal membrane with large pores, small pores, and aquaporin ultra-small pores. Label the peritoneum, mesothelium, blood vessels, and dialysate. Show the catheter anatomy with inner cuff in rectus muscle and outer cuff in subcutaneous tissue. Clean clinical illustration style with color-coded labels.

This diagram illustrates the key components of acute peritoneal dialysis:

Three exchange phases - Fill (dialysate in from bag above), Dwell (solute/fluid transfer across peritoneal membrane), Drain (spent dialysate out to collection bag)
Tenckhoff catheter anatomy - inner cuff anchored in the rectus muscle, outer cuff in subcutaneous tissue, coiled tip in the peritoneal cavity near the pouch of Douglas
Peritoneal membrane transport - diffusion of waste solutes (urea, creatinine, K⁺) from peritoneal capillaries into dialysate, and osmotic water removal through aquaporins driven by the dextrose gradient
Three-pore model - large pores (>150 Å) for proteins, small pores (40-45 Å) for small solutes, ultra-small pores/aquaporins (2-5 Å) for free water

indications and contraindications for chronic pd

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Indications and Contraindications for Chronic Peritoneal Dialysis

Indications

Primary Indication

Chronic PD is indicated for end-stage kidney disease (ESKD) requiring long-term renal replacement therapy (RRT). Most patients with ESKD are medically suitable for either PD or hemodialysis (HD); the choice is guided by patient preference, clinical factors, and social context. Patient preference is the primary factor in modality selection.

Conditions Where PD is Specifically Preferred or Advantageous

Clinical Situation	Why PD is Favored
Exhausted or poor vascular access	No vascular access needed; PD avoids the complications of AV fistulas/grafts/central lines
Cardiovascular instability / heart failure / severe cardiomyopathy	Gradual continuous fluid removal avoids the haemodynamic stress of intermittent HD sessions
Cirrhosis with ascites	PD allows controlled, continuous fluid and solute removal; cirrhosis may actually be better managed with CAPD
Infants and neonates	Central venous access is technically very difficult in small children; PD avoids this entirely
Children / pediatric ESKD	Better school attendance; more flexible schedule; PD preferred in younger children before kidney transplant
Patients who prefer home therapy	PD is performed at home; preserves autonomy and quality of life
Patients living far from HD centres	Eliminates need for 3x/week travel to dialysis centre
Residual kidney function preservation	PD is associated with slower decline in residual renal function compared to HD
Desire to avoid needles	PD is needle-free
Pregnancy with ESKD	PD can be used with supplemental HD to increase dialysis dose; some centres prefer it
Sickle cell disease with ESKD	Either PD or HD is viable; early nephrologist referral is key
Polycystic kidney disease (ADPKD)	PD can usually be performed despite enlarged kidneys, though risk of inguinal and umbilical hernias is increased
Rural / low-resource settings	Requires far less infrastructure than HD; adaptable to locally produced supplies
Diabetic patients (selected)	Continuous glucose-based dialysate allows steady glycaemic exposure; no heparin needed

National Kidney Foundation Primer, p. 611; Sabiston Textbook of Surgery; Comprehensive Clinical Nephrology, 7th ed.; Brenner and Rector's The Kidney

Contraindications

Contraindications to chronic PD are classified as absolute or relative.

Absolute Contraindications

Contraindication	Reason
Obliterated peritoneal cavity (e.g., dense intraperitoneal adhesions from multiple abdominal surgeries)	No functional peritoneal space for fluid instillation; catheter placement impossible or useless
Peritoneal membrane failure (e.g., encapsulating peritoneal sclerosis)	Membrane no longer capable of adequate solute or fluid transfer
Active abdominal infection / peritonitis (at time of catheter placement)	Risk of seeding catheter and worsening infection
Uncorrectable mechanical defects (e.g., large, irreparable diaphragmatic defects causing pleural communication; large untreatable hernias)	Dialysate cannot be retained in peritoneal cavity
Patient unable to perform or arrange PD (no caregiver support, severe cognitive impairment without assisted PD options)	PD is a self-managed therapy requiring training and compliance

Relative Contraindications (Barriers that can often be overcome)

Contraindication	Notes / Workarounds
Previous intraabdominal surgery	Most common barrier; adhesions may impair catheter function. Laparoscopic catheter placement with adhesiolysis can overcome this. Small bowel resections are particularly problematic
Obesity	Increased intra-abdominal pressure; higher hernia/leak risk; may need larger dialysate volumes. Presternal catheter placement can help
Ileostomy or colostomy	Exit-site placement must avoid stoma; infection risk is higher. Presternal catheters can avoid the problem
Renal transplant (prior)	Prior transplant operation may have created adhesions
Advanced age	Not a contraindication per se; assisted PD (nurse visits 1-2x/day) makes it feasible in the elderly
Diabetes mellitus (brittle/poorly controlled)	Continuous glucose absorption can worsen glycaemic control; icodextrin is an alternative osmotic agent. Brittle diabetes may favour in-centre HD
Congestive heart failure (severe)	Paradoxically, severe heart failure may actually favour PD (gradual fluid removal), but high-volume dwell may be poorly tolerated if intra-abdominal pressure affects diaphragmatic excursion
Hernias (inguinal, umbilical, incisional)	Raised intra-abdominal pressure from dialysate worsens hernias; surgical repair required before starting PD, or APD with lower fill volumes and dry days
Severe malnutrition / hypoalbuminaemia	Significant protein losses in dialysate further worsen nutrition
Inflammatory bowel disease	Active disease increases infection risk and may complicate catheter placement
Abdominal wall defects / recent abdominal surgery	Risk of leak; delay PD start; use low-volume exchanges initially
Respiratory insufficiency (severe)	Distension from dialysate dwell may impair diaphragmatic excursion and worsen hypoxia
Hearing impairment	APD machine alarms may be missed; use vibration or light alarms
Dementia / severe cognitive impairment	Requires assisted PD with trained caregiver
Social isolation (no home support)	Assisted PD or transitioning to HD is preferred

Sabiston Textbook of Surgery, The Biological Basis of Modern Surgical Practice; National Kidney Foundation Primer, p. 611; Campbell-Walsh Wein Urology

Summary: When to Choose PD vs. HD

Favour PD	Favour HD
Patient preference for home therapy	Patient preference for in-centre therapy
Poor vascular access	Poor peritoneal access or membrane function
Cardiovascular instability	Brittle diabetes requiring tight glucose control
Cirrhosis / severe cardiomyopathy	Prior extensive abdominal surgery with adhesions
Children, infants	Severe malnutrition or high protein loss
Remote location	Inadequate home environment or social support
Residual renal function preservation desired	Peritoneal membrane failure or encapsulating sclerosis
Needle phobia	Patient unable or unwilling to perform daily exchanges

Key principle (KDOQI 2019 Life-Plan): "The right access, for the right patient, at the right time, for the right reasons." - Sabiston Textbook of Surgery

Most people with ESKD are suitable for either modality. No randomised trial has demonstrated a consistent survival advantage for either PD or HD. PD is associated with superior health-related quality of life in comparative studies.

Comprehensive Clinical Nephrology, 7th ed., p. 2095

chronic pds and acute pds types

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