Key Facts

Dialysis is a life-sustaining treatment for ESRD. The choice between HD and PD depends on patient preference, lifestyle, residual renal function, and medical suitability. Both modalities have similar long-term survival outcomes.

Epidemiology

• ~30,000 patients on dialysis in the UK; ~60% HD, ~15% PD, ~25% transplanted
• Median survival on dialysis: 5-10 years overall; varies significantly by age and comorbidities
• UK Renal Registry data shows improving outcomes over time
• Increasing use of home HD and PD in line with NHS strategy

Indications for Dialysis Initiation

• Uraemic symptoms: nausea, vomiting, encephalopathy, pericarditis, neuropathy
• Refractory fluid overload unresponsive to diuretics
• Hyperkalaemia unresponsive to medical management
• Metabolic acidosis (pH <7.1) refractory to bicarbonate
• GFR typically 5-7 mL/min (or earlier if symptomatic)
• UK practice is generally to start dialysis based on symptoms rather than a specific GFR threshold (IDEAL trial)

Pathophysiology of Dialysis

Haemodialysis:

• Blood passes through a semipermeable membrane (dialyser) against dialysate flowing counter-current
• Solute removal by diffusion (concentration gradient) and convection (ultrafiltration)
• Fluid removal by hydrostatic pressure differential (ultrafiltration)

Peritoneal dialysis:

• Peritoneal membrane acts as the semipermeable membrane
• Dialysate instilled into peritoneal cavity via Tenckhoff catheter
• Solute removal by diffusion; fluid removal by osmosis (glucose-based dialysate creates osmotic gradient)
• Icodextrin-based dialysate for longer dwells

Indications for Urgent Dialysis (AEIOU)

• Acidosis: pH <7.1 refractory to bicarbonate
• Electrolytes: refractory hyperkalaemia (K+ >6.5 despite treatment)
• Intoxication: methanol, ethylene glycol, lithium, salicylates
• Overload: pulmonary oedema unresponsive to diuretics
• Uraemia: encephalopathy, pericarditis, neuropathy

HD Complications

• Intradialytic hypotension (most common): excessive ultrafiltration, autonomic dysfunction
• Cramps: electrolyte shifts, volume depletion
• Dialysis disequilibrium syndrome: headache, nausea, seizures (rapid urea clearance → cerebral oedema)
• Access complications: thrombosis, stenosis, infection, steal syndrome, aneurysm
• Air embolism: rare but life-threatening

PD Complications

• Peritonitis: cloudy effluent, abdominal pain, fever; WCC >100/mm³ with >50% neutrophils
• Exit-site/tunnel infection
• Hernias: inguinal, umbilical (increased intra-abdominal pressure)
• Encapsulating peritoneal sclerosis: rare, life-threatening; bowel encased in fibrous cocoon
• Membrane failure: loss of ultrafiltration capacity over years
• Protein loss: 5-15g/day of protein lost in dialysate

Red Flags

• Cloudy PD effluent → peritonitis → empirical IP antibiotics immediately
• AV fistula: absent thrill/bruit → thrombosis → urgent vascular referral
• New confusion on HD → dialysis disequilibrium or stroke

Pre-Dialysis Assessment

• eGFR: serial monitoring to plan dialysis access and preparation
• Immunisation: hepatitis B vaccination (enhanced schedule: 0, 1, 2, 6 months; check anti-HBs)
• Virology: hepatitis B, C, HIV screening
• Vein mapping: USS of upper limb veins for AV fistula planning
• Cardiac assessment: echocardiogram (volume status, cardiac function)

On Dialysis

• Monthly bloods: FBC, U&Es, calcium, phosphate, PTH, albumin
• Kt/V or URR: adequacy of HD (target Kt/V ≥1.2 or URR ≥65%)
• PD adequacy: weekly Kt/V ≥1.7, peritoneal equilibration test (PET)
• Access monitoring: clinical assessment, duplex USS for AV fistula/graft surveillance

PD Peritonitis

• Effluent: WCC (>100/mm³ with >50% neutrophils), Gram stain, culture
• Blood cultures: if systemically unwell

Haemodialysis

Access (in order of preference):

1. Radiocephalic AV fistula (Brescia-Cimino): wrist; create ≥6 months before dialysis
2. Brachiocephalic AV fistula: antecubital fossa
3. AV graft (synthetic PTFE): if veins unsuitable; higher infection/thrombosis risk
4. Tunnelled central venous catheter (Permcath): right IJV preferred; highest infection risk

Dialysis prescription:

• In-centre HD: 3×/week, 4 hours per session
• Home HD: may be daily (short or long sessions); improved outcomes
• Nocturnal HD: 6-8 hours overnight; best biochemical control
• High-flux membranes preferred for better middle-molecule clearance

Peritoneal Dialysis

• CAPD: 4 exchanges/day (2L; dwell time 4-6 hours; overnight 8-10 hours)
• APD: automated cycler overnight (8-10 hours); allows daytime freedom
• Icodextrin: for long dwell (improves ultrafiltration)

PD Peritonitis Treatment:

• Empirical: intraperitoneal vancomycin (loading 25mg/kg; maintenance 25mg/kg every 5 days) + IP gentamicin (0.6mg/kg)
• Guided by culture results; minimum 2 weeks treatment
• Fungal peritonitis: catheter removal + systemic antifungals (fluconazole/caspofungin)
• Catheter removal: refractory peritonitis (no response by day 5), fungal, mycobacterial

Supportive Care on Dialysis

• Anaemia: IV iron + ESAs (target Hb 100-120 g/L)
• Bone disease: phosphate binders, alfacalcidol, cinacalcet
• Cardiovascular: BP control, statin, fluid management
• Nutrition: dietitian input; adequate protein (1.0-1.2 g/kg/day HD, 1.2-1.3 PD)
• Vaccinations: hepatitis B, influenza, pneumococcal, COVID-19

Referral Criteria

• eGFR <20-25: refer for pre-dialysis education and access planning
• eGFR <15 or symptomatic: start RRT planning
• eGFR <5-7 or symptomatic: initiate dialysis

• Median survival on dialysis: ~5-10 years overall (highly age-dependent)
• 1-year survival: 85-90% (age-adjusted)
• 5-year survival: 40-60% (age-dependent)
• Cardiovascular disease is the leading cause of death on dialysis (~40%)
• HD vs PD: similar long-term outcomes; PD may have survival advantage in first 1-2 years
• IDEAL trial: starting dialysis late (symptomatic, GFR ~5) vs early (GFR ~10) showed no survival difference
• Home HD: associated with improved outcomes and quality of life vs in-centre HD
• Transplantation offers significantly better survival and quality of life than any form of dialysis

HD vs PD Comparison

AV Fistula Complications