Polycystic Kidney Disease

Introduction

Polycystic kidney disease (PKD) is a group of inherited kidney diseases in which the kidneys develop multiple cysts instead of normal renal tissue. There are two main subtypes, with different patterns of inheritance, namely autosomal dominant PKD and autosomal recessive PKD.

Autosomal Dominant Polycystic Kidney Disease

Also known as adult polycystic kidney disease, arises due to mutations in the PKD1 and PKD2 genes on chromosomes 16 and 4 respectively. It is one of the most-common conditions with monogenic inheritance affecting approximately 1 in 1000 people.

Presentation

  • Signs of renal failure
  • Abdominal pain
  • Haematuria, due to a cyst bleeding
  • Hypertension
  • Renal colic
  • Signs of infection (infected cyst)

There are also extra-renal manifestations such as liver cysts, intracranial (Berry) aneurysm and mitral valve prolapse, which may manifest as sudden severe headache (subarachnoid haemorrhage) or a heart murmur (mitral regurgitation)

History

Symptoms as above may not become apparent until middle-age, and patients may present as late until the 40s or 50s.

As there is autosomal dominant inheritance, usually patients will have one affected parent, although new mutation is possible.

Examination

Grossly enlarged kidneys may result in abdominal pain on balloting the kidneys, and these may be palpable on examination.

Laboratory investigations

A U+E blood test may show raised creatinine, urea and reduced eGFR, indicating various degrees of renal impairment and CKD. Genetic testing can be done if a definite diagnosis is required or radiological investigation is unclear.

Radiological Investigations

Ultrasound or CT of the kidneys showing large, cystic kidneys usually confirms the diagnosis.

Management

  • Regular monitoring of blood pressure (target 130/80)
  • Anti-hypertensives (ACEi most commonly used)
  • Reduce salt and caffeine intake, increase water intake
  • Prepare for renal replacement therapy (dialysis or transplant)

Autosomal recessive polycystic kidney disease

ARPKD is a much rarer condition, affecting approximately 1 in 40,000 and is due toa mutation in the PKDHD1 gene on chromosome 6.

Presentation is in infancy with polyuria, hypertension and abdominal mass. Severe cases may present with oligohydramnios during pregnancy and die shortly after birth, while a small number will survive into adulthood, developing end-stage renal failure during adolescence.

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