• Clinical science

Polycystic kidney disease

Abstract

Polycystic kidney disease (PKD) is an inherited disorder in which multiple cysts develop in the kidneys. The WHO classification recognizes two distinct disorders: autosomal recessive PKD (ARPKD), which is associated with a short life expectancy that rarely surpasses childhood, and autosomal dominant PKD (ADPKD), which is associated with a reduced life expectancy in adulthood. The severity of symptoms varies significantly depending on the underlying disorder. Onset of ARPKD is usually in infancy or childhood, with patients presenting with pulmonary insufficiency and progressive renal failure. Patients with ADPKD, on the other hand, typically present with flank pain, arterial hypertension, and progressive kidney disease in adulthood. Early diagnosis and treatment may prevent or delay end stage renal disease. Kidney transplantation is the only curative treatment option.

Epidemiology

  • Incidence
    • ADPKD: ∼ 1/1,000; one of the most common inherited kidney diseases in humans
    • ARPKD: ∼ 1/20,000

References:[1][2]

Epidemiological data refers to the US, unless otherwise specified.

Classification

Overview of the WHO classification

Etiology Characteristics Age of onset
Autosomal recessive polycystic kidney disease (ARPKD) Inherited: mutation on chromosome 6
  • Bilateral
  • Equally sized cysts
  • Obligate hepatic involvement
Birth to childhood
Autosomal dominant polycystic kidney disease (ADPKD) Inherited: mutation on chromosome 16 (85% of cases) or 4 (15% of cases) with an alteration of polycystin-1 or 2
  • Bilateral
  • Cysts vary in size
  • Multiple extrarenal manifestations
Adulthood (typically age > 30 years)

References:[3][1]

Clinical features

Autosomal recessive polycystic kidney disease (ARPKD)

Autosomal dominant polycystic kidney disease (ADPKD)

References:[1][4][5][2][6]

Diagnostics

References:[3][2]

Pathology

  • ARPKD: cystic dilatation of the collecting ducts (other nephron segments are usually not affected) and hepatic fibrosis
  • ADPKD: progressive cystic dilatation of the tubular system; hepatic cysts; gastrointestinal, CNS, and cardiovascular involvement (see also “Symptoms/Clinical findings” above)

References:[5]

Differential diagnoses

Multicystic dysplastic kidneys

  • Definition: renal dysplasia with multiple cystic dilatation of nephrons during embryonic development
  • Etiology: : unclear; sporadic occurrence during embryonic development of the ureter and nephrons (rarely with a positive family history)
  • Clinical features
    • Onset: birth to childhood
    • Rarely symptomatic; large cysts might impair urinary output
    • Renal insufficiency is rare.
    • Extrarenal manifestations:
  • Ultrasound: unilateral (rarely bilateral) cysts of varying size
  • Treatment: See “Therapy” below.

Obstructive cystic dysplasia

Medullary sponge kidney

Renal cysts

  • Definition: solitary or multiple renal cysts
  • Diagnosis: usually benign incidental finding during CT or ultrasound examinations
    • Round or oval anechoic cysts (black = fluid) and dorsal sound amplification
    • If ultrasound findings are unusual (e.g., internal echoes, poorly delimited or thickened cyst wall), malignant diseases should be considered as a differential diagnosis.
  • Treatment
    • Not indicated in most cases
    • Indication for surgery: symptomatic cysts (e.g., impaired urinary flow, pain) or risk of further complications
  • Rare complications: ruptured cysts, cyst infection, and compression of adjacent tissue

References:[7][8][9][10][11]

The differential diagnoses listed here are not exhaustive.

Treatment

References:[12]

Prognosis

  • ARPKD
    • Neonates with severe cystic dilatation have a poor life expectancy; rarely survive > 1 month after birth
    • The majority of children who survive infancy have a life expectancy > 15 years; the prognosis depends on the extent of renal and hepatic impairment.
  • ADPKD

References:[1][5]