Cystic diseases of the Kidney

NB Renal cysts are common, especially in older patients.  They are usually incidental findings and rarely require any management (they can occasionally cause pain and haematuria if they rupture)

Adult Polycystic Kidney Disease

Background / Epidemiology

  • Autosomal dominant condition caused by mutations in the PKD1 gene (85%) or PKD2 gene (15%)
    • Most patients with PKD1 mutations cause end stage renal disease and usually presents at around age 55
    • Only a minority of patients with PKD2 mutations end up with renal failure; they also usually present later at around 70 years.
  • Common- incidence of around 1 in 1000; accounts for 10-15% of patients on dialysis

Presentation

  • Hypertension may be an early sign (~age 20)
  • Vague abdominal/loin discomfort with a palpable mass (often bilateral)
    • Acute pain or renal colic may be due to cyst rupture
  • Haematuria (rarely proteinuria)- usually gross episodes which resolve spontaneously, although microscopic haematuria usually remains
  • Urinary tract/cyst infections
  • Chronic kidney disease
  • Extrarenal manifestations
    • About 30% also have liver cysts although impairment of function is rare (may have hepatomegaly
    • About 10% have cerebral berry aneurysms and are at risk of subarachnoid haemorrhage (probably restricted to certain mutations)
    • Mitral and aortic regurgitation and LV hypertrophy is frequent but usually mild
    • Patients may have features of polycythaemia (increased EPO production)

Investigations

  • USS of the kidney is usually diagnostic
    • FBC, U&Es and LFTs should be done routinely to check renal and hepatic function

Management

  • As with CKD- management of cardiovascular risk factors is important e.g. hypertension control
  • Unless they cause severe pain or infection, the kidneys are usually not removed.
  • If kidney function deteriorates, patients usually do well on dialysis.

Medullary Sponge Kidney

  • Cystic disease of the papillary collecting ducts
  • Not seem to be genetic (aetiology unknown)
  • Patients usually present with recurrent renal stone disease (often require preventative management)
  • Diagnosed by USS or IVU
  • Management is usually focussed at preventing UTI and stone disease
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