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Polycystic Kidney Disease (ADPKD/ARPKD)

TL;DR

Nephro: Polycystic Kidney Disease (ADPKD/ARPKD) is a high-yield MRCP Part 1 topic focusing on genetics, imaging, and extra-renal complications. ADPKD presents in adulthood with renal cysts, hypertension, and aneurysm risk, while ARPKD presents in infancy with hepatic fibrosis and portal hypertension. Exam questions commonly test differences in inheritance, clinical features, and complications. Prioritise recognising patterns and avoiding common traps.


Why this matters

Polycystic kidney disease is a repeatedly tested topic in MRCP Part 1, spanning nephrology, genetics, and radiology. Questions typically assess your ability to differentiate autosomal dominant (ADPKD) from autosomal recessive (ARPKD) disease, identify extra-renal features, and manage complications.

For structured revision, see the MRCP Part 1 overview and consolidate learning with Free MRCP MCQs.


Core sections

1) Genetics and pathophysiology

  • ADPKD

    • Autosomal dominant inheritance

    • Mutations: PKD1 (85%), PKD2 (15%)

    • Defective polycystin proteins → abnormal tubular cell proliferation → cyst formation

  • ARPKD

    • Autosomal recessive inheritance

    • Mutation: PKHD1

    • Defective fibrocystin → cystic dilatation of collecting ducts + hepatic fibrosis

Exam tip: PKD1 = more severe disease with earlier progression to ESRD.

2) Age of presentation

  • ADPKD: Usually presents in 3rd–5th decade

  • ARPKD: Presents in neonates or infancy (often antenatal detection)

3) Renal manifestations

  • Bilateral enlarged kidneys with multiple cysts

  • Hypertension (early and common in ADPKD)

  • Haematuria (often after minor trauma due to cyst rupture)

  • Flank pain

  • Recurrent urinary tract infections

  • Progressive chronic kidney disease → ESRD

4) Extra-renal manifestations (high-yield table)

Feature

ADPKD

ARPKD

Liver

Hepatic cysts

Congenital hepatic fibrosis

Brain

Berry aneurysms → SAH risk

Rare

Heart

Mitral valve prolapse

Rare

Pancreas

Cysts possible

Rare

Lungs

—

Pulmonary hypoplasia (neonatal)

5) Imaging findings

  • Ultrasound: First-line investigation

  • CT/MRI: More sensitive for small cysts and complications

Diagnostic criteria (ADPKD):

  • Age <40: ≥3 cysts (total)

  • Age 40–59: ≥2 cysts in each kidney

6) Key complications

  • Hypertension (major contributor to disease progression)

  • Intracranial aneurysm → subarachnoid haemorrhage

  • Cyst infection

  • Nephrolithiasis (often uric acid stones)

  • Progressive renal failure

7) Management principles

  • Blood pressure control: ACE inhibitors or ARBs

  • Tolvaptan: Slows cyst growth in selected patients

  • Treat infections with antibiotics that penetrate cysts (e.g., fluoroquinolones)

  • Manage complications (stones, pain)

  • Renal replacement therapy for ESRD

Screening:

  • Intracranial aneurysm screening in high-risk individuals (family history, high-risk professions)

8) High-yield exam points (rapid revision)

  1. ADPKD = adult onset + cysts + aneurysms

  2. ARPKD = childhood disease + hepatic fibrosis

  3. PKD1 worse than PKD2

  4. Early hypertension is typical

  5. Haematuria after trauma → cyst rupture

  6. Hepatic cysts ≠ hepatic fibrosis

  7. Berry aneurysm → SAH risk

  8. Tolvaptan slows progression

  9. Family history is key in ADPKD

  10. ARPKD associated with portal hypertension


Practical examples / mini-cases

MCQA 32-year-old man presents with hypertension and intermittent haematuria. His father died of a “brain bleed”. Ultrasound shows enlarged kidneys with multiple cysts.

What is the most likely associated complication?

A. Portal hypertensionB. Berry aneurysmC. Pulmonary hypoplasiaD. Renal tubular acidosisE. Nephrocalcinosis

Answer: B. Berry aneurysm

Explanation: This is classic ADPKD. The family history of “brain bleed” strongly suggests a berry aneurysm, a key extra-renal complication. Portal hypertension is seen in ARPKD.


Medical students discussing high-yield nephrology topics including ADPKD and ARPKD for MRCP Part 1

Common pitfalls (5 bullets)

  • Confusing hepatic cysts (ADPKD) with hepatic fibrosis (ARPKD)

  • Assuming ADPKD always presents late—hypertension can be early

  • Missing intracranial aneurysm risk

  • Using standard UTI antibiotics for cyst infection (poor penetration)

  • Forgetting severity difference between PKD1 and PKD2


FAQs

1) When should intracranial aneurysm screening be done in ADPKD?

Screen patients with a family history of aneurysm or subarachnoid haemorrhage, high-risk occupations, or prior to major surgery.

2) What is the key difference between ADPKD and ARPKD?

ADPKD presents in adulthood with cysts and aneurysms, whereas ARPKD presents in infancy with hepatic fibrosis and portal hypertension.

3) Is tolvaptan used in all patients?

No, it is reserved for rapidly progressive ADPKD due to cost and risk of hepatotoxicity.

4) What is the main cause of death in ADPKD?

Cardiovascular complications, especially related to hypertension.

5) Are liver cysts dangerous?

Usually benign but may cause symptoms due to mass effect or infection.


Ready to start?

Reinforce this topic with active recall and exam-style practice. Start with Free MRCP MCQs and test your readiness using Start a mock test. For a complete roadmap, revisit the MRCP Part 1 overview and integrate this with related topics like haematuria and CKD progression.


Sources

 
 
 

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