History of Peritoneal Dialysis

Precursors (1740s)

Early Experimental Era (1920s)

First Clinical Success (1940s)

Intermittent PD and Technical Refinements (1950s-1960s)

Automation and the Cycler (1960s-1970s)

CAPD: The Landmark Innovation (1976-1978)

Automated PD and Modern Era (1980s-present)

• Icodextrin (a glucose polymer) for long dwells
• Amino acid-based solutions
• Bicarbonate/bicarbonate-lactate buffers (lower glucose degradation products) ...were introduced to better preserve the peritoneal membrane.

• Better connectology (Y-set and twin-bag systems) to reduce peritonitis rates
• Peritoneal equilibration testing (PET) to characterize membrane transport type and tailor prescriptions
• Assisted PD programs enabling elderly and disabled patients to receive PD with nurse or caregiver help at home
• Improved outcomes data from registries (USRDS, ANZDATA, PDOPPS) guiding prescriptions

Key Figures at a Glance

PD Apparatus, Solutions, Transfer Sets, Connectology, Access (Catheter), and Exit Site Care

1. PD APPARATUS

1.1 Manual Exchange System (CAPD)

• PD bag (typically 2 L) containing dialysate, connected via tubing
• A transfer set/extension tubing that connects the bag to the catheter
• A clamp and titanium or plastic connector
• No electricity or machine is required

1.2 Automated PD Cycler (APD Machine)

• Pump - drives controlled inflow and outflow of dialysate through cassette or peristaltic pump
• Heating element - warms dialysate bags to body temperature (37°C) before infusion
• Weighing or volumetric system - measures fill and drain volumes accurately per cycle
• Programmable controller - operator or clinician programs: dwell volume, dwell time, number of cycles, last fill (or "dry" day)
• Alarm system - alarms for drain failure, occlusion, low fill, patient disconnect
• Cassette/tubing set - single-use, sterile disposable tubing set that connects dialysate bags to the cycler and to the patient's catheter
• Bags - typically 5-L bags are used for overnight cycling; up to 15 L total dialysate used per session

2. PD SOLUTIONS (DIALYSATE)

2.1 Standard Glucose-Based Solutions (Conventional)

• Increased inward glucose absorption → worsening hyperglycemia in diabetics
• GDP accumulation → peritoneal membrane damage with long-term use
• Dyslipidemia, insulin resistance, obesity

2.2 Icodextrin Solution

• Osmotic agent: Icodextrin - a glucose polymer (starch-derived, high molecular weight polysaccharide)
• Buffer: Lactate
• pH: Physiologic (5.8-6.4)
• Concentration: 7.5%

• Superior ultrafiltration in high/high-average transporters compared to 2.5-4.25% glucose during long dwells
• Regression of left ventricular hypertrophy (through better volume control)
• Better glycemic control and insulin sensitivity
• Reduced total body water

• Skin rash (exfoliating, palms/soles) - occurs 2-3 weeks after starting, resolves on stopping
• False high glucose readings - glucometers using glucose dehydrogenase pyrroloquinoline quinone (GDH-PQQ) will overestimate blood glucose due to accumulated maltose (icodextrin metabolite); extreme caution is required to prevent inadvertent insulin administration
• Aseptic peritonitis - rare, linked historically to peptidoglycan contamination from manufacturing; largely eliminated with process improvements

2.3 Low-GDP (Biocompatible) Glucose Solutions

• Buffer: Lactate, but mixed just before infusion to minimize GDPs
• pH: Physiologic (~7.0-7.4)
• GDPs: Undetectable or very low

2.4 Bicarbonate-Based Solutions

• Buffer: Bicarbonate (physiologic buffer) ± small amount of lactate
• pH: Neutral (~7.2-7.4)
• More complete correction of metabolic acidosis
• Reduced infusion pain (a common complaint with acidic conventional solutions)
• No conclusive evidence for better peritoneal membrane preservation

2.5 Amino Acid Solution

• Osmotic agent: 1.1% amino acids (provides ultrafiltration equivalent to 1.5% glucose)
• Buffer: Lactate
• Used as a single exchange in malnourished PD patients for nutritional supplementation
• Part of "glucose-sparing" regimens (reducing total daily glucose load)
• Risk: may worsen pre-existing azotemia or acidosis if used too frequently

2.6 Glucose-Sparing Regimens

1. 3 exchanges of 1.5% glucose (CAPD)
2. Replace overnight (long dwell) with icodextrin
3. Replace one daytime exchange with amino acid solution

3. TRANSFER SETS AND CONNECTOLOGY

3.1 Components of the Transfer Set

• A length of PD-grade silicone or polyurethane tubing (typically 30-40 cm long)
• A clamp on the tubing to prevent dialysate flow when not exchanging
• A connector end that attaches to the catheter's titanium adapter
• A disconnect cap or bag spike at the other end

3.2 Historical Evolution of Connectology

1. Connect the Y-set to the catheter
2. Drain first (drain old dialysate into the drain bag)
3. Flush a small volume of new dialysate through the drain line (the "flush-before-fill" step - flushes any introduced bacteria to the drain, not into the patient)
4. Fill fresh dialysate from the new bag into the peritoneum
5. Disconnect the Y-set and cap the catheter

3.3 Twin-Bag / Double-Bag System

• Eliminates the need to attach separate bags
• Reduces connections and disconnections (fewer touch events)
• Is now the standard for CAPD
• Combines flush-before-fill + disconnect system in a single device

3.4 Disconnect Systems

3.5 APD Connectology

• A single-use sterile cassette (in most modern machines)
• Connected via a spike connection to 2-5 dialysate bags
• Connected to the patient's transfer set via a sterile luer-lock or push-pull connector

4. ACCESS FOR PD: THE PD CATHETER

4.1 Catheter Materials and Basic Design

• An intraperitoneal segment with multiple side holes and/or end holes for fluid distribution
• One or two Dacron felt cuffs - fibrous polyester cuffs that anchor the catheter in tissue; fibrous ingrowth seals the tract against bacteria
• A subcutaneous tunnel segment between the deep cuff and exit site
• An external segment exiting through the skin

4.2 Catheter Designs

• Straight or coiled intraperitoneal segment (coiled design reduces infusion pain by distributing the jet effect of flow)
• Single cuff or double cuff (double cuff is preferred - deep cuff in rectus muscle, superficial cuff ~2-3 cm from skin)
• Deep cuff prevents intraperitoneal leaks; superficial cuff reduces infection tracking along the tunnel

• The external segment has a permanent downward-facing curve ("swan-neck" shape)
• Directs the exit site downward, which promotes drainage of any discharge away from the site
• Reduces cuff extrusion and improves catheter survival compared to straight-exit Tenckhoff
• Recommended by ISPD guidelines as the preferred design

• The external segment is tunneled subcutaneously to exit at the presternal (chest) location rather than the abdomen
• Particularly beneficial for: obese patients, patients with abdominal stomas, children in diapers, patients with fecal incontinence
• Associated with decreased exit site infection and peritonitis rates
• Access survival of up to 95% at 2 years reported

• Has two silicone discs in the intraperitoneal segment
• The discs act as flanges, anchoring the catheter tip within the pelvis and reducing tip migration

• Coiled tip has multiple holes distributed over a larger area
• Reduces localized jet pain during fill
• May be slightly more prone to tip migration

4.3 Catheter Insertion Techniques

• Under general or regional anesthesia
• Direct visualization of catheter placement
• Most widely used historically but associated with higher rates of infection and outflow failure vs. minimally invasive methods

• Most used by nephrologists
• Uses the same fluoroscope and disposables as central venous catheter placement
• Ultrasound guides an 18-21 gauge needle into the peritoneum
• Contrast injection produces "spider web" pattern confirming intraperitoneal position
• A guidewire is advanced, dilators track over it, and the catheter is inserted through a peel-away sheath
• Deep cuff placed in rectus muscle; tunnel and exit site created with a tunneling tool
• Requires local anesthesia ± conscious sedation (midazolam + fentanyl)
• Associated with fewer complications than open surgical technique in randomized studies

• Single puncture using a 2.2-mm diameter optical peritoneoscope
• Air (600-1000 mL) insufflated for visualization
• Allows direct inspection of peritoneal surfaces for adhesions, hernias
• Trocar-cannula with spiral sheath inserted through rectus muscle at 45°; sheath dilated to 6 mm; catheter passed through dilated sheath with internal stylet
• Deep cuff implanted in rectus muscle with implanter tool (no dissection of anterior rectus sheath)
• Advantages: local anesthesia, less tissue dissection, lower rates of infection/outflow failure/pericatheter leak, immediate use possible for intermittent PD

• General anesthesia; multiple port sites; CO₂ insufflation
• Best for patients with prior abdominal surgery, adhesions, hernias
• Allows advanced techniques: omentopexy (omentum tacked away from catheter), hernia repair, adhesiolysis
• Results in improved long-term catheter success

4.4 Optimal Timing of Catheter Insertion

• Catheter placed when GFR falls below 10 mL/min/1.73 m², aiming to start dialysis at GFR 7-8 mL/min/1.73 m²
• Allow 2-4 weeks between insertion and routine dialysis use (for wound healing, cuff ingrowth, leak prevention)
• If urgent start is required, low-volume PD can begin within 24 hours of insertion (with the patient recumbent)
• Catheter should not be used for 10-14 days; should be flushed 2-3 times/week with saline or dialysate until training

4.5 Burying (Embedding) the Catheter (Moncrief Technique)

• Catheter inserted in standard fashion, tunneled to a 1-cm skin exit site, filled with heparin 1000 U/mL, then the external tip is redirected back into the subcutaneous space toward the midline
• Primary incision and exit site are closed over the catheter
• Benefits: tissue ingrowth into cuffs is undisturbed; no exit site to care for; eliminates early infection; catheter can be placed electively months before it is needed
• Exteriorization: small incision through original exit site, catheter located with hemostats and brought out; can be successfully exteriorized years after placement

5. EXIT SITE CARE

5.1 Anatomy of the Exit Site and Tunnel

• Exit site: the skin opening where the catheter emerges
• Sinus tract: the tissue channel between exit site and superficial cuff
• Subcutaneous tunnel: the tissue path between the two cuffs
• A mature, healthy exit site is epithelialized, dry, non-tender, with no discharge

5.2 Post-Insertion Wound Care (Early Phase - First 4-6 Weeks)

1. The original post-surgical dressing is kept in place for 5-7 days after insertion (removed only for frank bleeding or excessive drainage)
2. Dressing changes performed using sterile technique by trained PD staff wearing masks
3. Non-occlusive gauze dressings are preferred over transparent occlusive dressings (gauze allows drainage away from the exit site; occlusive dressings trap moisture)
4. The catheter must be immobilized - taped securely to prevent traction injury (traction injury is a risk factor for exit site infection)
5. The transfer set is taped separately, away from the dressing, for catheter access without disturbing the wound
6. Cytotoxic agents must be avoided during healing: povidone-iodine and hydrogen peroxide damage healing tissue and should not be used
7. The patient should NOT take over exit site care until the exit site is fully healed (typically 4-6 weeks)

5.3 Chronic/Ongoing Exit Site Care (After Healing)

1. Wash hands thoroughly before touching the catheter
2. Inspect the exit site for signs of infection: redness, swelling, crusting, sanguinous or purulent discharge, pain
3. Cleanse the exit site with a non-irritating, non-toxic agent:
   • Chlorhexidine gluconate 2% is widely recommended - applied in a circular outward motion (not probed into the sinus)
   • Allow to air dry ~30 seconds
   • Avoid iodine, hydrogen peroxide, alcohol (impair skin cell turnover)
4. Apply topical prophylactic antibiotic to the exit site (see section 5.4)
5. Place a sterile gauze pad under the catheter at the exit site (catheter rests on gauze, not skin)
6. Apply a final sterile dressing (gauze + hypofix or mepore)
7. Tape/anchor the catheter to the skin in a comfortable position, minimizing tension on the exit site; catheter and transfer set may be looped and secured with an immobilizer

• Avoid scratching or picking at the exit site or removing scabs forcibly
• Do not sleep on the abdomen
• Cover the exit site when swimming (sea water or well-maintained pools only, per ISPD physical activity guidelines)
• Masks and gloves are not required for chronic exit site care by the patient at home (clean technique); sterile technique is required during the healing phase

5.4 Topical Prophylactic Antibiotics (Exit Site)

5.5 Exit Site Scoring (Assessment)

5.6 Exit Site Infection (ESI)

• First-line empiric (pending culture): oral agent effective against S. aureus (e.g., flucloxacillin, dicloxacillin, cloxacillin; first-gen cephalosporin if penicillin-allergic)
• Minimum 2 weeks of treatment; 3 weeks for Pseudomonas
• Pseudomonas ESI is particularly difficult - often requires two antibiotics simultaneously
• If gram-negative: ciprofloxacin 500-750 mg once daily orally
• MRSA: systemic vancomycin
• Systemically unwell: IV antibiotics ± hospitalization
• No improvement at 7 days → ultrasound to exclude tunnel abscess
• No complete healing at 4 weeks → consider cuff shaving (exteriorizing and trimming the outer cuff)
• Persistent/relapsing ESI → catheter removal (high risk of peritonitis)

5.7 Prevention Summary (ISPD Framework)