Dialysis — How It Works, Benefits & Recovery — Procedure Guide, Recovery & Risks | MyMedicPlus

Dialysis is a life-sustaining renal replacement therapy (RRT) that artificially replicates the kidney's filtration function when chronic kidney disease (CKD) progresses to end-stage renal disease (ESRD) — typically defined as GFR below 10–15 mL/min/1.73m² with uraemic symptoms. Two principal modalities exist: haemodialysis (HD), which filters blood outside the body through an artificial kidney (dialyser membrane), and peritoneal dialysis (PD), which uses the peritoneal membrane lining the abdominal cavity as a natural semipermeable filter. A third option — kidney transplantation — is the preferred long-term renal replacement strategy for eligible patients, offering superior survival and quality of life compared to any form of dialysis. Dialysis does not cure kidney disease but prevents the fatal complications of untreated ESRD: uraemia, hyperkalaemia, acidosis, and pulmonary oedema from fluid overload. Approximately 3.7 million people receive dialysis globally, with numbers increasing by 6–8% annually as rates of diabetes and hypertension — the two leading causes of renal failure — continue to rise worldwide. In the United Kingdom, approximately 26,000 patients receive regular haemodialysis and 6,000 receive peritoneal dialysis. The choice between modalities is individualised based on the patient's home circumstances, residual renal function, comorbidities, and personal preference — supported by specialist nephrology nursing and patient education.

Dialysis is initiated for ESRD when the kidney GFR falls below 10–15 mL/min/1.73m² in the presence of uraemic symptoms (nausea, vomiting, anorexia, pericarditis, encephalopathy), or urgently for life-threatening complications regardless of GFR level. Urgent dialysis indications include: hyperkalaemia with potassium above 6.5 mmol/L with ECG changes (peaked T-waves, broad QRS, sine-wave pattern); severe metabolic acidosis with pH below 7.1 or bicarbonate below 12 mmol/L unresponsive to medical therapy; refractory pulmonary oedema from fluid overload not responding to diuretics; and acute uraemic encephalopathy or pericarditis. Elective preparation for dialysis begins at CKD Stage 4 (GFR 15–29) to allow creation of vascular access (arteriovenous fistula formation, requiring 6–12 weeks of maturation) or peritoneal dialysis catheter placement. Common underlying causes of ESRD requiring dialysis include diabetic nephropathy (35%), hypertensive nephropathy (25%), glomerulonephritis (15%), and polycystic kidney disease (5%). Appropriate referral to nephrology at CKD Stage 3b or earlier ensures optimal preparation and reduces emergency dialysis starts, which are associated with worse outcomes.

Haemodialysis: blood is drawn from the patient's arteriovenous fistula (AVF), arteriovenous graft (AVG), or central venous tunnelled dialysis catheter via two needles or catheter lumens at flow rates of 200–400 mL/min into the extracorporeal circuit. The blood passes through a hollow-fibre dialyser (semi-permeable cellulose or synthetic membrane with surface area 1.0–2.1 m²), where diffusion removes uraemic solutes (urea, creatinine, potassium, phosphate, uric acid) down concentration gradients into the dialysate solution flowing counter-currently on the opposite side of the membrane. Excess fluid accumulated between sessions is removed by ultrafiltration — applying transmembrane pressure across the membrane. The cleaned, fluid-reduced blood returns to the patient via the return needle or lumen. Sessions typically last 3.5–5 hours, delivered three times per week (Monday-Wednesday-Friday or Tuesday-Thursday-Saturday schedule). Anticoagulation with unfractionated or low-molecular-weight heparin prevents clotting in the circuit. Peritoneal dialysis: 1.5–3 litres of sterile glucose-based dialysate is instilled through a permanently implanted Tenckhoff peritoneal catheter (tunnelled through the abdominal wall into the peritoneal cavity). The dialysate dwells in the abdomen for 4–8 hours (CAPD manual exchanges) or overnight (automated peritoneal dialysis, APD). Solutes diffuse across the peritoneal membrane from blood into the dialysate; fluid is removed by osmosis driven by the glucose concentration gradient. CAPD requires 3–4 manual exchanges daily; APD uses a cycler machine performing 4–6 automated overnight exchanges while the patient sleeps, with a daytime dwell.

Dialysis markedly prolongs survival and prevents the fatal complications of untreated ESRD. Without dialysis or transplantation, death from uraemia occurs within days to weeks. Haemodialysis patients in the United States (USRDS data) have a 5-year survival of approximately 35–40% overall, improving to 60–70% in patients aged 20–44 years. Peritoneal dialysis achieves similar or marginally better survival to in-centre HD in the first 2–3 years, particularly in younger patients with residual renal function who benefit from the continuous solute clearance PD provides. Home haemodialysis (nocturnal or frequent short daily sessions) achieves substantially better cardiovascular outcomes, blood pressure control, quality of life, and haemoglobin levels compared to conventional thrice-weekly in-centre HD. Kidney transplantation provides dramatically superior 5-year survival exceeding 90% in living-donor recipients — making dialysis primarily a bridge therapy for patients awaiting transplantation. Adequate dialysis relieves uraemic symptoms within days, restores appetite, improves neurological function, and enables resumption of activities of daily living for most patients. Erythropoietin therapy initiated alongside dialysis corrects anaemia in 90% of patients.

Haemodialysis risks: intradialytic hypotension (excessive fluid removal rate) affects 10–30% of sessions and is managed by adjusting ultrafiltration rate, sodium profiling, and dietary sodium restriction. Muscle cramps, headaches, and post-dialysis fatigue ('dialysis hangover') are common and improve with adequacy optimisation. Vascular access complications are the leading cause of HD morbidity: AVF failure to mature (25–30% of newly formed fistulae), AVF stenosis or thrombosis requiring radiological intervention, and central catheter-related bacteraemia (approximately 1–3 episodes per 1,000 catheter-days) — the leading preventable cause of dialysis mortality. Long-term cardiovascular disease accounts for 40–50% of dialysis deaths and is driven by hypertension, fluid overload, anaemia, hyperphosphataemia, and dialysis-related vascular calcification. Other long-term complications include renal osteodystrophy (secondary hyperparathyroidism, vascular calcification), dialysis amyloidosis from beta-2 microglobulin accumulation (carpal tunnel syndrome, destructive spondyloarthropathy), and persistent malnutrition (serum albumin below 35 g/L — a strong predictor of mortality). Peritoneal dialysis risks include bacterial peritonitis (0.3–0.5 episodes per patient-year), exit-site and tunnel infection, catheter malfunction requiring replacement, inadequate solute clearance in high transporters, and ultrafiltration failure over time.

Haemodialysis patients typically experience 1–3 hours of fatigue after each session as the body readjusts to fluid and electrolyte shifts, particularly in the initial weeks. This inter-dialytic fatigue improves as the patient adapts and their dialysis prescription is optimised. Strict dietary adherence is essential between sessions: potassium restriction (avoid bananas, tomatoes, potatoes, oranges — target potassium below 5.5 mmol/L pre-dialysis); phosphate restriction (limit dairy, nuts, whole grains, cola drinks — take prescribed phosphate binders with every meal); fluid restriction (500–1,000 mL per day above urine output — target inter-dialytic weight gain under 1 kg/day); and sodium restriction to reduce thirst and fluid accumulation. Medications include sevelamer or calcium carbonate phosphate binders, erythropoietin-stimulating agents (darbepoetin or epoetin) for anaemia, alfacalcidol (vitamin D analogue) for secondary hyperparathyroidism, and antihypertensives. Fistula care requires daily assessment of the thrill and bruit, protection from compression (no blood pressure cuffs or tight clothing on the fistula arm), and immediate reporting of pain, swelling, or absent thrill. Peritoneal dialysis patients perform monthly clinic reviews for adequacy assessment (Kt/V urea clearance target above 1.7), nutritional status, membrane transport characterisation, and catheter care review. Both modalities require vigilant monitoring of blood tests (monthly haematology, biochemistry, PTH, ferritin) and regular nephrologist review.