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Dialysis: Haemodialysis vs Peritoneal

TL;DR

Nephro: Dialysis: Hemodialysis vs. Peritoneal is a high-yield MRCP Part 1 topic focusing on mechanisms, indications, and complications. Haemodialysis provides rapid extracorporeal clearance, whereas peritoneal dialysis offers slower, continuous toxin removal using the peritoneum. Exam questions commonly test complication profiles and clinical selection. Focus on contrasts rather than isolated facts for maximum scoring.


Why this matters

Dialysis is a core nephrology topic in MRCP Part 1, frequently appearing in both standalone and integrated clinical questions. Candidates are expected to understand not only the physiology but also the clinical decision-making behind choosing haemodialysis (HD) versus peritoneal dialysis (PD).

A structured approach—mechanism, indications, complications, and patient selection—helps simplify this topic. Start with the MRCP Part 1 overview and reinforce concepts using Free MRCP MCQs.


Core sections

1. Basic Principles

  • Haemodialysis (HD)


    Blood is circulated through an external dialyser where solutes and fluid are removed before returning to the body.

  • Peritoneal Dialysis (PD)


    The peritoneum acts as a semipermeable membrane; dialysate is infused and later drained.

👉 Conceptual shortcut:

  • HD = artificial kidney outside the body

  • PD = natural membrane inside the body

2. Mechanism of Solute Removal

Feature

Haemodialysis

Peritoneal Dialysis

Membrane

Synthetic dialyser

Peritoneum

Clearance

Rapid

Gradual

Ultrafiltration

Hydrostatic pressure

Osmotic (glucose-based)

Frequency

Intermittent (3× weekly)

Continuous

Setting

Hospital/centre-based

Home-based

3. Indications for Dialysis (AEIOU)

A classic MRCP Part 1 favourite:

  1. Acidosis (refractory metabolic acidosis)

  2. Electrolyte imbalance (especially hyperkalaemia)

  3. Intoxication (e.g. lithium, methanol, ethylene glycol)

  4. Overload (fluid overload resistant to diuretics)

  5. Uraemia (e.g. pericarditis, encephalopathy)

👉 HD is preferred in emergencies due to rapid clearance.

4. Access Types

  • Haemodialysis

    • Arteriovenous (AV) fistula (gold standard)

    • Central venous catheter (temporary)

  • Peritoneal Dialysis

    • Tenckhoff catheter

👉 High-yield: AV fistula complications (infection, thrombosis, high-output cardiac failure).

5. Complications (Most Tested Area)

Haemodialysis

  • Hypotension (most common)

  • Dialysis disequilibrium syndrome

  • Infection (vascular access)

  • Bleeding (heparin use)

Peritoneal Dialysis

  • Peritonitis (most important)

  • Protein loss → malnutrition

  • Hyperglycaemia

  • Hernias

👉 Key exam trigger:

  • Cloudy dialysate = peritonitis until proven otherwise

6. Advantages and Disadvantages

Haemodialysis✔ Rapid correction of biochemical abnormalities✔ Suitable for acute kidney injury✖ Haemodynamic instability✖ Requires hospital visits

Peritoneal Dialysis✔ Greater independence (home therapy)✔ Better cardiovascular stability✖ Risk of infection (peritonitis)✖ Less efficient clearance

7. Patient Selection

Peritoneal dialysis preferred:

  • Children

  • Poor vascular access

  • Cardiovascular instability

Haemodialysis preferred:

  • Acute kidney injury

  • Severe hyperkalaemia

  • Toxic ingestions

8. Five Most Tested Subtopics

  1. AEIOU indications

  2. Differences in ultrafiltration mechanisms

  3. Dialysis disequilibrium syndrome

  4. PD peritonitis (presentation + organisms)

  5. Vascular access complications


Practical examples / mini-cases

MCQ

A 65-year-old patient on peritoneal dialysis presents with abdominal pain and cloudy dialysate. Temperature is 38.2°C.

What is the most likely diagnosis?

A. Bowel perforationB. Peritoneal dialysis-associated peritonitisC. Acute pancreatitisD. Uraemia

Answer: B – Peritoneal dialysis-associated peritonitis

Explanation: Cloudy dialysate is a hallmark of PD-associated infection. Common organisms include Staphylococcus epidermidis. Immediate intraperitoneal antibiotics are required. This is a classic MRCP Part 1 question stem.


Student studying with books, coffee, and laptop

Common pitfalls (5 bullets)

  • Confusing ultrafiltration mechanisms (pressure vs osmotic)

  • Missing dialysis disequilibrium syndrome (HD-specific)

  • Assuming PD is suitable in acute emergencies

  • Ignoring cloudy dialysate as a key clue

  • Forgetting metabolic effects of glucose in PD


Study-tip checklist

  • ✅ Memorise AEIOU indications

  • ✅ Compare HD vs PD in table format

  • ✅ Learn 3 complications per modality

  • ✅ Practise regularly with Free MRCP MCQs

  • ✅ Attempt timed exams via Start a mock test

  • ✅ Integrate dialysis with AKI and CKD topics


FAQs

1. Which dialysis is preferred in emergencies?

Haemodialysis is preferred due to rapid solute and fluid removal, especially in hyperkalaemia and toxin ingestion.

2. What is the most common complication of haemodialysis?

Hypotension, due to rapid fluid shifts, is the most commonly tested complication.

3. What indicates peritonitis in PD patients?

Cloudy dialysate with abdominal pain is the key clinical sign.

4. What is dialysis disequilibrium syndrome?

A neurological complication of HD caused by rapid urea removal leading to cerebral oedema.

5. Can peritoneal dialysis be used in acute kidney injury?

It can be used, but haemodialysis is generally preferred for faster correction in acute settings.


Ready to start?

Dialysis is a predictable scoring area in MRCP Part 1 when approached systematically. Strengthen your concepts through the MRCP Part 1 overview and test your understanding using Free MRCP MCQs. Build exam confidence with a timed Start a mock test.


Sources

 
 
 

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