Peritoneal Dialysis

Peritoneal dialysis (PD) is a home-based renal replacement therapy that harnesses the peritoneal membrane — a large (1.7–2.0 m²) serosal surface lining the abdominal cavity — as a biological dialyser. A sterile dialysate is instilled into the peritoneal cavity via a surgically implanted Tenckhoff catheter, and solute clearance occurs via diffusion and convection, while water removal (ultrafiltration) is driven by osmotic gradients created by dextrose or icodextrin.

PD is a well-established modality in Australia and New Zealand. According to the Australia and New Zealand Dialysis and Transplant Registry (ANZDATA 2023), approximately 1,900 patients are on prevalent PD in Australia, representing roughly 12% of the total dialysis population. PD utilisation is disproportionately higher in regional and remote communities where facility haemodialysis access is limited.

Key advantages of PD over facility haemodialysis include: preservation of residual renal function, dietary and fluid flexibility, reduced need for vascular access, greater patient autonomy, and comparable survival outcomes in the first 2–4 years (particularly in non-diabetic patients). The two principal modalities — continuous ambulatory peritoneal dialysis (CAPD) and automated peritoneal dialysis (APD) — offer flexibility to suit lifestyle, transport, and clinical requirements.

Mechanisms of Solute and Water Transport

PD relies on two fundamental transport processes:

• Diffusion: Solutes move down concentration gradients across the peritoneal membrane. Small molecules (urea, potassium, creatinine) equilibrate quickly; larger molecules (β₂-microglobulin) clear more slowly.
• Ultrafiltration (UF): Osmotic agents in dialysate — dextrose (1.36%, 2.27%, 3.86%) or icodextrin 7.5% — draw water into the peritoneal cavity. Net UF depends on dwell time, membrane transport status (PET category), and lymphatic absorption.

Continuous Ambulatory Peritoneal Dialysis (CAPD)

CAPD involves 4–5 manual exchanges per day with dwell times of 4–6 hours during the day and a single overnight dwell of 8–10 hours. Each exchange uses 1.5–3 L of dialysate.

Automated Peritoneal Dialysis (APD)

APD uses a cycler machine to deliver multiple short exchanges overnight (6–10 h). During the day, the patient may remain "dry" (tidal mode) or carry a day dwell (continuous cycling PD / CCPD). APD is the most common PD modality in Australia (~65% of PD patients).

CAPD vs APD — Comparative Overview

Peritoneal Equilibration Test (PET)

The PET stratifies patients by membrane transport characteristics using a 2.27% dextrose exchange with 4-hour dwell. Dialysate-to-plasma creatinine ratio (D/P Cr) at 4 hours classifies transporters:

• High: D/P Cr ≥ 0.81 — rapid solute equilibration; benefits from short dwell APD
• High-average: D/P Cr 0.65–0.80
• Low-average: D/P Cr 0.50–0.64
• Low: D/P Cr < 0.50 — slow equilibration; suits CAPD with long dwells

A standard PET should be performed at 4–6 weeks post-initiation and repeated annually or when adequacy declines.

Tenckhoff Catheter

The straight or coiled double-cuff Tenckhoff catheter is the standard PD access device in Australia. Cuffs (Dacron felt) promote tissue ingrowth and anchor the catheter subcutaneously, providing a bacterial barrier.

Insertion Techniques

Pre-Operative Preparation

• Nasal Staphylococcus aureus decolonisation: mupirocin nasal ointment 2% BID for 5 days pre-procedure (reduces S. aureus exit-site infection by 60–80%)
• Peri-operative antibiotics: single-dose IV first-generation cephalosporin (cefazolin 2 g IV) or vancomycin 1 g IV if MRSA colonised
• Bowel preparation: routine use is centre-dependent; some recommend low-residue diet + stool softeners
• Bladder decompression: ensure patient voids or insert catheter pre-operatively to reduce bowel/bladder injury risk
• Pre-operative PET not required — perform after break-in

Break-In Period & Initial Exchanges

• Minimum 2-week healing period before routine PD use (reduce pericatheter leak)
• Day 0–14: flush-and-fill with 500–1,000 mL heparinised saline (500 U/L) 2–3 times per week (or daily), draining immediately — this trains the patient while avoiding intraperitoneal pressure
• If urgent dialysis needed before break-in completes, low-volume APD (1–1.5 L) may be attempted with caution
• Avoid constipation (stool softeners, macrogol) — straining increases hernia and catheter migration risk

Exit-Site Care

Daily exit-site care with topical antibiotic cream is a standard of care in Australia:

• First-line: Mupirocin 2% cream applied to exit site daily (reduces exit-site infection by ~50%)
• Alternative: Gentamicin 0.1% cream if mupirocin resistance suspected
• Keep exit site dry; cover with sterile dressing post-shower until healed
• Secure catheter to avoid traction; use a catheter belt

Peritonitis is the most common serious complication of PD and the leading cause of catheter loss and transfer to haemodialysis. The International Society for Peritoneal Dialysis (ISPD) 2022 guidelines and Australian PD unit protocols form the basis of management.

Diagnostic Criteria

Peritonitis is diagnosed when at least two of the following are present:

• Clinical features: abdominal pain, cloudy effluent, fever, nausea/vomiting
• Peritoneal effluent WBC > 100/μL (or > 0.1 × 10⁹/L) with ≥ 50% polymorphonuclear cells
• Positive effluent culture (may be negative in 15–20% of cases)

Specimen Collection

• Obtain effluent sample before administering antibiotics
• Send for cell count (WBC, differential), Gram stain, culture (aerobic + anaerobic), and sensitivity
• Use blood culture bottles: inoculate 10 mL effluent into each of aerobic and anaerobic bottles at bedside (increases culture yield by ~20%)
• If cloudy effluent with negative culture, consider fungal culture, TB culture, unusual organisms, or chemical peritonitis

Causative Organisms — Australian Patterns

Empiric Antibiotic Therapy

Commence empiric antibiotics immediately after effluent collection. In Australia, ISPD 2022–compliant regimens use intraperitoneal (IP) delivery as standard:

Directed Therapy (Post-Culture)

Catheter Removal Indications

• Refractory peritonitis: no clinical improvement after 5 days of appropriate antibiotics
• Relapsing peritonitis (same organism within 4 weeks of completing therapy)
• Fungal peritonitis — remove catheter immediately
• Concurrent exit-site/tunnel infection (refractory or S. aureus)
• Bowel perforation with peritonitis
• Recurrent peritonitis (>3 episodes)

Exit-Site & Tunnel Infection

Defined by purulent or serous discharge ± erythema at the catheter exit site; tunnel infection involves tenderness/erythema along the subcutaneous tunnel.

• Swab discharge for culture before starting treatment
• Empiric: oral cephalexin 500 mg QID or flucloxacillin 500 mg QID (MSSA); add oral rifampicin 300 mg BD if MRSA suspected
• Pseudomonas: oral ciprofloxacin 500 mg BD ± IP ceftazidime
• Consider catheter removal if no response at 2–3 weeks or concurrent peritonitis

Dialysis Adequacy Assessment

PD adequacy is measured by urea clearance (Kt/V) and creatinine clearance (CrCl), normalised to body water and body surface area respectively. Targets are set by ISPD and adapted in Australian PD units:

Prescription Modification for Inadequate Clearance

• Increase fill volume (e.g. 2.0 → 2.5 L per exchange)
• Add an extra exchange (CAPD: 4 → 5 exchanges)
• For APD: increase cycle number, use tidal mode, add a daytime exchange
• Use icodextrin for long dwells to improve UF without dextrose load
• Preserve residual renal function: avoid nephrotoxins (NSAIDs, aminoglycosides systemically), avoid hypotension
• If anuric and Kt/V remains below target despite maximising prescription, consider transfer to haemodialysis

Complications of PD

Membrane Failure

Peritoneal membrane failure may manifest as:

• Loss of ultrafiltration (< 400 mL/4h with 3.86% dextrose)
• High transporter status on repeat PET (D/P Cr > 0.81) — suggests membrane damage
• Inadequate solute clearance despite maximal prescription

Options: modify prescription (shorter dwells, icodextrin), add APD, or consider conversion to haemodialysis or renal transplantation.

Nutritional Considerations

• Protein intake: 1.0–1.2 g/kg/day (higher than HD due to peritoneal losses of 5–15 g/day protein + amino acids)
• Energy intake: 25–35 kcal/kg/day (including dextrose absorbed from dialysate)
• Potassium: generally liberal unless hyperkalaemic (PD removes potassium)
• Sodium restriction: 80–100 mmol/day for volume management
• Phosphate: dietary restriction + phosphate binders (sevelamer, lanthanum, calcium carbonate — PBS-listed)
• Regular dietitian review (minimum 6-monthly)

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