Dialysis and Kidney Transplant

When a person's kidneys fail, the body cannot clear the metabolic waste, excess water, acid, and potassium that ordinary living produces every hour. Left untreated, this is uniformly fatal within days to weeks. Renal replacement therapy — dialysis and transplantation — is one of medicine's great success stories: it is the reason that "kidney failure" changed within a single generation from a death sentence into a chronic condition that millions of people live with for decades. This page teaches how each modality actually works, when to choose which, what goes wrong, and how the field was born from wartime improvisation and surgical daring.

Learning Objectives

• Explain the physical principles (diffusion, convection, ultrafiltration, osmosis) that make dialysis clear solutes and remove fluid.
• Compare hemodialysis and peritoneal dialysis on mechanism, access, schedule, adequacy, and complications.
• List the indications for starting dialysis, including the emergency "AEIOU" criteria.
• Describe the essentials of kidney transplantation: donor sources, HLA matching, immunosuppression, and rejection.
• Recount the history from Willem Kolff's rotating-drum kidney to the 1954 Murray transplant, and why each step mattered.
• Recognise the major complications of each modality and how they are managed.

Quick Answer

Dialysis substitutes for the kidney's filtering function by moving solutes across a semipermeable membrane. Hemodialysis (HD) pumps blood through an external filter (dialyzer) and is usually done three times weekly, typically requiring an arteriovenous fistula. Peritoneal dialysis (PD) uses the patient's own peritoneal membrane, with dialysate instilled into the abdomen through a catheter and exchanged several times daily at home. Neither replaces the kidney's endocrine functions well, and both are inferior to a working kidney. Transplantation — placing a living or deceased donor kidney into the recipient's iliac fossa — offers the best survival and quality of life but requires lifelong immunosuppression and a matched, available organ. The choice among them depends on the patient's physiology, lifestyle, comorbidity, and organ availability.

Where It Came From

For most of history, kidney failure meant death. The intellectual seed was laid in 1861 when Thomas Graham, a Scottish chemist, described dialysis — the separation of crystalloids from colloids across a parchment membrane — and coined the term. But the concept sat unused clinically for 80 years because no one could build a device that safely handled human blood without clotting or infection.

The breakthrough came from Willem Kolff, a young Dutch physician, during the German occupation of the Netherlands in World War II. Working with scarce materials — sausage casing (cellophane) as the membrane, an aluminium drum, and a water bath — Kolff built the first practical rotating-drum artificial kidney in 1943. His early patients almost all died, partly because heparin and access were primitive. Then in 1945 he treated a 67-year-old woman in uremic coma from acute kidney injury; she woke up, regained kidney function, and lived years more. It was the first life unequivocally saved by dialysis. Kolff, remarkably, gave away his machine designs freely, and after the war shipped units abroad, seeding the field worldwide.

Two later engineering problems had to be solved before dialysis became a chronic therapy rather than a one-time rescue. Belding Scribner in Seattle solved repeated access in 1960 with the Scribner shunt — a Teflon-and-Silastic tube left in the arm connecting an artery to a vein — so a patient could be dialyzed again and again without destroying vessels each time. This turned dialysis into a maintenance treatment and immediately created the wrenching ethical problem of who to select for scarce machines (the famous Seattle "God Committee"). Peritoneal dialysis matured separately; the modern ambulatory form (CAPD) was described by Popovich and Moncrief in 1976.

Transplantation followed a parallel arc. Early 20th-century attempts using animal and unmatched human kidneys all failed from rejection, which was not understood until Peter Medawar's immunology work in the 1940s–50s. The decisive moment was 23 December 1954 in Boston, when Joseph Murray and colleagues transplanted a kidney between identical twins (Ronald and Richard Herrick) — sidestepping rejection entirely because the twins were genetically identical. The recipient lived eight years. Murray won the Nobel Prize in 1990. The subsequent development of immunosuppression (azathioprine, steroids, and later ciclosporin in the 1980s) made transplantation between unrelated people routinely possible.

How Dialysis Works: The Physics

Every dialysis modality exploits a semipermeable membrane that lets small solutes and water pass but holds back cells and large proteins. Three transport processes do the work:

• Diffusion — solutes move from high to low concentration. Blood full of urea and potassium sits on one side; fresh dialysate with none of these sits on the other, so waste diffuses out. This is the dominant clearance mechanism in conventional HD.
• Ultrafiltration / convection — a pressure gradient drives water across the membrane, dragging dissolved solutes with it ("solvent drag"). This is how excess fluid is removed, and it clears larger "middle molecules" better than diffusion.
• Osmosis — in PD, a high concentration of glucose (or icodextrin) in the dialysate pulls water out of the blood across the peritoneum osmotically.

Dialysate composition is deliberately engineered: low or zero potassium and urea to create diffusion gradients, a controlled bicarbonate level to correct acidosis, and calibrated sodium and calcium.

Hemodialysis

Blood is drawn from the patient at 300–450 mL/min, anticoagulated (usually with heparin), and pumped through a dialyzer — a cartridge of thousands of hollow fibres bathed in countercurrent dialysate — then returned. A typical session lasts about 4 hours, three times a week.

The critical practical issue is vascular access, ranked by preference:

1. Arteriovenous (AV) fistula — a surgeon connects an artery to a vein (e.g. radiocephalic at the wrist), and over 6–8 weeks the vein "arterializes," becoming thick and high-flow so it can be needled repeatedly. Best long-term option: lowest infection and clot rates.
2. AV graft — a synthetic tube bridging artery and vein when native vessels are inadequate; usable sooner but higher thrombosis/infection.
3. Central venous catheter — inserted into the internal jugular; immediate but the highest rate of infection (line sepsis) and central vein stenosis. A catheter is a bridge, not a destination.

Worked example: A man on maintenance HD arrives having missed his weekend session, breathless, with a potassium of 6.8 mmol/L and peaked T waves on ECG. This is a dialysis emergency. He is given IV calcium gluconate to stabilise the myocardium, insulin-dextrose and salbutamol to shift potassium into cells temporarily, and then urgent hemodialysis — the only step that actually removes potassium from the body. Within an hour of dialysis his potassium falls and the ECG normalises.

Complications during HD include hypotension (from removing fluid too fast), muscle cramps, and — if a large uremic load is cleared too quickly in a first session — dialysis disequilibrium syndrome (cerebral oedema from osmotic shifts; prevented by short, gentle initial treatments).

Peritoneal Dialysis

Here the patient is the machine. A permanent Tenckhoff catheter is tunnelled into the peritoneal cavity. Sterile dialysate (typically 2 L) is instilled, left to "dwell" for hours while solutes diffuse across the richly vascularised peritoneal membrane and glucose osmosis draws off fluid, then drained and replaced.

Two schedules exist:

• CAPD (continuous ambulatory PD): the patient performs ~4 manual exchanges per day; no machine, fully home-based.
• APD (automated PD): a cycler machine performs exchanges overnight while the patient sleeps.

PD's advantages are freedom (done at home, no needles, gentler on the heart with steadier fluid removal, preserves residual kidney function longer). Its signature complication is peritonitis — the dialysate returns cloudy, the abdomen is tender, and cell counts confirm infection; it is treated with intraperitoneal antibiotics. Recurrent peritonitis, catheter failure, or encapsulating peritoneal sclerosis (a rare, serious scarring of the peritoneum after years of PD) can force a switch to HD.

Renal Transplantation

A transplant restores all kidney functions — filtration and endocrine (erythropoietin, vitamin D activation) — and gives the best survival and quality of life. The donated kidney is placed not where the native kidneys are, but in the iliac fossa (extraperitoneally), with its artery and vein joined to the iliac vessels and the ureter implanted into the bladder. The patient's own diseased kidneys are usually left in place.

Donor sources: living donors (related or unrelated) give the best graft survival and can be scheduled electively; deceased donors are either after brain death (DBD) or circulatory death (DCD).

Matching aims to minimise rejection:

• ABO blood group compatibility (though ABO-incompatible transplants are now possible with pre-conditioning).
• HLA (human leukocyte antigen) matching — the closer the match at HLA-A, -B, and -DR loci, the better.
• A crossmatch test ensures the recipient has no pre-formed antibodies against the donor, which would cause immediate hyperacute rejection.

Immunosuppression is lifelong and typically triple-therapy: a calcineurin inhibitor (tacrolimus or ciclosporin), an antiproliferative (mycophenolate), and corticosteroids, often with induction agents at the time of surgery.

Rejection comes in three forms:

• Hyperacute — minutes to hours, from pre-formed antibodies; prevented by crossmatching, essentially untreatable if it occurs.
• Acute — days to months, cell- or antibody-mediated; treated with high-dose steroids or antibody therapy.
• Chronic — months to years, progressive graft fibrosis and vascular injury; the main cause of long-term graft loss.

The cost of immunosuppression is real: increased infection (including opportunistic organisms like CMV and BK virus, and Pneumocystis), and increased cancer risk (especially skin cancers and post-transplant lymphoproliferative disorder). Patients balance these risks against a life free of dialysis.

Real-World Applications

• Modality counselling: A young, independent patient who works full-time may thrive on home APD or a pre-emptive living-donor transplant, avoiding dialysis entirely. A frail elderly patient with poor vessels and heart failure may be better served by carefully chosen HD — or, importantly, by conservative (non-dialysis) management focused on symptom control, which for some very frail patients offers similar survival with better quality of life.
• Emergency medicine: Recognising the indications for urgent dialysis — remembered as AEIOU: refractory Acidosis, Electrolytes (hyperkalaemia), Intoxications (dialyzable poisons like methanol, ethylene glycol, salicylates, lithium), fluid Overload (pulmonary oedema), and Uremia (pericarditis, encephalopathy).
• Public health and ethics: Organ shortage drives paired kidney exchange programmes, opt-out donor registration in some countries, and continuing debate over allocation fairness — the direct descendant of Scribner's original selection dilemma.

Common Mistakes

1. "Dialysis cures kidney failure." It does not. Standard HD provides only about 10–15% of normal kidney clearance and poorly replaces endocrine functions. It is life-sustaining maintenance, not a cure — only a transplant restores near-normal function.
2. "You give calcium to lower potassium in hyperkalaemia." Calcium does not lower potassium; it stabilises the cardiac membrane to prevent arrhythmia while other measures (insulin-dextrose, then dialysis) actually reduce the potassium. Confusing these can be fatal.
3. "A dialysis catheter is as good as a fistula." Catheters carry far higher infection and thrombosis rates. A fistula is the preferred long-term access; "Fistula First" is a guiding principle, and catheters should be temporary.
4. "The old kidneys are removed during transplant." Usually they are left in place; the new kidney goes into the iliac fossa. Native nephrectomy is done only for specific reasons (e.g. chronic infection, huge polycystic kidneys, refractory hypertension).
5. "Transplant means no more medication." The opposite — it means lifelong, non-negotiable immunosuppression, missing which risks acute rejection and graft loss.

Comparison and Connections

Feature	Hemodialysis	Peritoneal Dialysis	Transplant
Membrane used	Artificial dialyzer	Own peritoneum	N/A (whole organ)
Main transport	Diffusion + ultrafiltration	Diffusion + osmosis	Physiological
Access	AV fistula / graft / catheter	Tenckhoff catheter	Iliac vessel anastomosis
Setting	Usually in-centre, 3x/week	Mostly home, daily	One-time surgery
Signature complication	Hypotension, access infection	Peritonitis	Rejection, infection, cancer
Endocrine function replaced	Poorly	Poorly	Yes
Survival/quality of life	Good	Good	Best

Dialysis and transplant are not rivals but a continuum: many patients start on dialysis, receive a transplant, and may return to dialysis if the graft eventually fails. Understanding this connects to chronic kidney disease staging and progression and to acute kidney injury, where dialysis may be temporary.

Practice Questions

Recall

Q: Name the physical process primarily responsible for solute clearance in conventional hemodialysis, and the one primarily responsible for fluid removal in peritoneal dialysis. A: Diffusion clears solutes in HD; osmosis (driven by glucose in the dialysate) removes fluid in PD.

Understanding

Q: Why is an AV fistula preferred over a central venous catheter for long-term hemodialysis? A: A fistula provides high, reliable blood flow with far lower rates of infection and thrombosis than a catheter, which is prone to line sepsis and central vein stenosis. Fistulas last longer and have better outcomes, hence "Fistula First."

Application

Q: A patient with acute kidney injury develops a potassium of 7.2 mmol/L with ECG changes unresponsive to insulin-dextrose. Which single intervention definitively removes potassium from the body, and which AEIOU criterion does this satisfy? A: Urgent hemodialysis definitively removes potassium (medical therapy only shifts or stabilises). This satisfies the "E" (electrolytes/hyperkalaemia) indication for emergency dialysis.

Analysis

Q: A 30-year-old with a well-functioning transplant stops his tacrolimus for a month because he "felt fine." Two weeks later his creatinine rises sharply and a biopsy shows cellular infiltrate. Explain what happened and why the "felt fine" reasoning is dangerous. A: Feeling well reflects that the graft was working, not that immunosuppression was unnecessary. Stopping tacrolimus allowed T-cell–mediated acute rejection, which is often asymptomatic until graft function declines. Immunosuppression prevents an ongoing immune attack; adherence is required indefinitely, and this episode risks permanent graft damage.

FAQ

Is dialysis painful? The treatment itself is not painful once access is established, though needling a fistula causes a brief sting. Complications like cramps or hypotension during HD can be uncomfortable; PD is needle-free.

How long can someone live on dialysis? Many people live 5–10 years or considerably longer on dialysis; some have survived over 30 years. Survival depends heavily on age, heart disease, and other conditions rather than dialysis alone.

Can I choose home dialysis? Often yes. Both peritoneal dialysis and home hemodialysis let suitable patients treat themselves at home, offering flexibility and, for many, better quality of life. It requires training and a suitable home setup.

How long do transplanted kidneys last? On average a deceased-donor kidney lasts roughly 10–15 years and a living-donor kidney longer, but this varies widely. Chronic rejection and recurrence of the original disease are the main long-term threats.

Why not just transplant everyone? Donor organs are scarce, not everyone is fit for major surgery and lifelong immunosuppression, and some patients have high antibody levels making matching very hard. Dialysis remains essential for those waiting or unsuitable for transplant.

Does dialysis fix anaemia and bone problems? Only partly. Because dialysis poorly replaces the kidney's hormone functions, patients still usually need erythropoietin injections, iron, vitamin D analogues, and phosphate binders — problems a transplant largely resolves.

Quick Revision

• Kidney failure is fatal untreated; renal replacement = dialysis or transplant.
• Kolff built the first artificial kidney (1943), first life saved 1945; Scribner shunt (1960) enabled chronic HD; Murray did the first successful (twin) transplant, 23 Dec 1954.
• HD: dialyzer + dialysate, diffusion clears solutes, ultrafiltration removes fluid; fistula is best access.
• PD: uses own peritoneum, osmosis (glucose) removes fluid; main risk is peritonitis.
• Emergency dialysis = AEIOU: Acidosis, Electrolytes (K+), Intoxications, Overload, Uremia.
• Hyperkalaemia: calcium stabilises the heart; insulin/dextrose shifts K+; dialysis removes it.
• Transplant: iliac fossa, native kidneys left in; needs ABO/HLA match, crossmatch, lifelong immunosuppression.
• Rejection: hyperacute (minutes), acute (days–months), chronic (years). Immunosuppression raises infection and cancer risk.

Related Topics

Prerequisites

• Chronic Kidney Disease
• Acute Kidney Injury

Related Topics

• Fluid, Electrolyte, and Acid-Base Balance
• Immunology of transplantation (see Immunology)

Next Topics

• Glomerular diseases and their recurrence after transplant
• Complications of long-term immunosuppression