Polycystic Kidney Disease

Question 1

Define

Answer 1

Autosomal dominant inherited disorder characterised by the development of multiple renal cysts that gradually expand and replace normal kidney substance
Variably associated with extra-renal (liver and CV abnormalities)

Question 2

Causes

Answer 2

• 85% caused by mutations in PKD1 on chromosome 16

This is a membrane-bound multidomain protein involved in cell-cell and cell-matrix interactions

• 15% caused by mutations of PKD2 on chromosome 4

Pathophysiology

Proliferative/hyperplastic abnormality of the tubular epithelium

Early on, the cysts are connected to the tubules from which they arise and the fluid content is glomerular filtrate

When cyst diameter >2 mm, they detach from the tubule and the fluid content is derived from secretion of the lining epithelium

With time, the cysts enlarge and cause progressive damage to adjacent functioning nephrons

Question 3

Epidemiology

Question 4

Symptoms

Answer 4

usually present 30-40 years

May be asymptomatic

• Pain in flanks – due to cyst enlargement/bleeding, stone, blood clot migration, infection
• Haematuria  HTN

Extra-renal → liver cysts
Associated with intracranial berry aneurysms and may present with sudden onset headache (subarachnoid haemorrhage) Also associated with mitral valve prolapse, ovarian cysts and diverticular disease

Question 5

Signs

Answer 5

Abdominal distension

• Bilateral, enlarged cystic kidneys
• Palpable liver
• HTN
• Signs of chronic renal failure at a later stage
• ±Signs of aortic aneurysm or aortic valve disease

Question 6

Investigations

Answer 6

US or CT

• Will show multiple cysts bilaterally in enlarged kidneys
• Liver cysts may also be seen