Harvey's Garden

Polycystic kidney disease

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It is classified into two distinct disorders: autosomal recessive PKD (ARPKD) and autosomal dominant PKD (ADPKD).

Epidemiology

ADPKD: The most common inherited cause of chronic kidney disease

Etiology

  • ADPKD
    • PKD1 on chromosome 16 (85% of cases)
    • PKD2 on chromosome 4 (15% of cases)
  • ARPKD
    • Mutation in PKHD1 gene on chromosome 6

Mnemonic

Polycystic Kidney = 16 letters! = Chromosome 16

Pathophysiology

Formation and expansion of cysts in the renal cortex and medulla → compression of renal vessels with activation of the renin-angiotensin-aldosterone system (RAAS), ischemia, and destruction of the kidney parenchyma

Clinical features

  • ADPKD (Adult-onset):
    • Asymptomatic until 30s-40s.
    • HTN: Often the earliest sign (due to cyst ischemia causing ↑ RAAS activation). c
    • Renal: Flank/abd pain (cyst rupture/infection), gross/microscopic hematuria, bilateral palpable flank masses. c
    • Nephrolithiasis (uric acid or calcium oxalate).
  • ARPKD (Infantile-onset):
    • Prenatal: Oligohydramnios leading to Potter sequence (pulmonary hypoplasia, flat facies, clubfeet).
    • Neonatal/Infant: Massive bilateral flank masses, severe respiratory distress (from pulm hypoplasia), severe HTN.

Diagnostics

FeatureADPKD (Adult)ARPKD (Infantile)
GenePKD1/PKD2PKHD1
OnsetAdulthood (30-40s)In Utero / Infancy
PresentationHTN, flank pain, hematuriaPotter sequence, neonatal respiratory distress
Liver DiseaseHepatic cystsCongenital hepatic fibrosis, portal HTN
Key AssociationBerry aneurysmsPulmonary hypoplasia
PrognosisESRD ~age 60High neonatal mortality; ESRD in childhood
  • ADPKD:
    • Initial/Confirmatory: Renal Ultrasound (US). Diagnostic criteria based on age + number of cysts (e.g., ≥3 cysts per kidney if age 15-39).
    • Key Labs: UA (hematuria, proteinuria), CMP (progressive ↑ BUN/Cr).
    • Advanced Imaging: CT/MRI abd/pelvis used if US is equivocal or to assess cyst complications (hemorrhage vs infection).
    • Note: Routine screening for berry aneurysms (MRA/CTA brain) is ONLY indicated if high-risk (e.g., family hx of SAH, previous rupture, high-risk occupation).
  • ARPKD:
    • Prenatal: Fetal US (bilateral enlarged, echogenic kidneys + oligohydramnios).
    • Postnatal Initial: Renal US (diffuse microcysts, loss of corticomedullary differentiation) + Hepatic US (fibrosis).
    • Genetic Testing: Gold standard if US findings are ambiguous.

Treatment

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