What are the diagnostic and treatment approaches for polycystic kidney disease in adults?

Diagnosis of Autosomal Dominant Polycystic Kidney Disease (ADPKD) in Adults

For adults with suspected ADPKD, abdominal ultrasound is the recommended first-line diagnostic imaging modality, with specific age-dependent cyst criteria for diagnosis. 1

Diagnostic Approach Based on Family History

Adults with Positive Family History

• Ultrasound diagnostic criteria:

  • Ages 15-39 years: ≥3 total kidney cysts confirms ADPKD; ≤1 cyst rules it out
  • Ages 40-59 years: ≥2 cysts in each kidney confirms ADPKD; ≤2 total cysts rules it out
  • Age ≥60 years: ≥4 cysts in each kidney confirms ADPKD 1

• When ultrasound is equivocal or shows atypical features:

  • Proceed to MRI or CT imaging
  • MRI criteria: >10 total cysts confirms ADPKD; <5 total cysts rules it out (ages 16-40) 1
  • Consider genetic testing for definitive diagnosis 1

Adults with Incidentally Detected Kidney/Liver Cysts

• For multiple cysts, discordant imaging/GFR, or atypical findings:

  • Proceed to MRI/CT imaging
  • Consider genetic testing (PKD1, PKD2, and other cystic kidney disease genes) 1

• For few cysts with normal kidney function and size:

  • Follow-up imaging in approximately 2 years 1

Genetic Testing Indications

Genetic testing is particularly valuable in:

• Cases with few kidney cysts
• Variable intrafamilial disease severity
• Very-early-onset ADPKD
• Discordant imaging and GFR
• Negative family history
• Young (<30 years) living-related kidney donors at risk
• Family planning considerations 1

Disease Severity Assessment

• Mayo Imaging Classification (MIC) is recommended to predict future kidney function decline and timing of kidney failure 1
  • Divides patients into typical (class 1) and atypical (class 2) ADPKD
  • For class 1 patients, stratifies into 5 groups (1A-1E) indicating accelerating decline in kidney function
  • Requires height-adjusted total kidney volume measured by MRI or CT

Prognostic Factors

Several factors affect disease severity:

• Genetic factors: PKD1 mutations cause more severe disease than PKD2
• Mutation type: Truncating PKD1 mutations are more severe than non-truncating
• Sex: Males typically have more severe disease
• Environmental factors: Obesity and high salt intake worsen prognosis 1

Common Diagnostic Pitfalls

1. Misdiagnosis in young adults: Ultrasound may miss small cysts in young adults; MRI is more sensitive but should be used judiciously 1

2. Overlooking other cystic kidney diseases: Several inherited diseases can mimic ADPKD with kidney/liver cysts 1

3. Failing to assess extrarenal manifestations: ADPKD commonly affects other organs, particularly the liver (polycystic liver disease is the most common extrarenal manifestation) 1, 2

4. Inadequate family screening: Parental examination may reveal previously undetected ADPKD 1

5. Underestimating solitary cysts: In children with positive family history, even a solitary cyst is highly suggestive of ADPKD 1

Management Considerations After Diagnosis

• Blood pressure control: Target BP ≤110/75 mmHg in adults aged 18-49 with CKD G1-G2; <120 mmHg systolic in adults ≥50 or with CKD G3-G5 3

• First-line antihypertensive therapy: ACE inhibitors or ARBs 3

• Lifestyle modifications:

  • Sodium restriction
  • High water intake
  • Regular exercise (150 minutes/week moderate-intensity)
  • Maintaining healthy weight 3

• Regular monitoring:

  • Office and home blood pressure measurements
  • eGFR and albuminuria/proteinuria assessment
  • Judicious use of imaging for disease monitoring 3

By following these diagnostic algorithms and understanding the prognostic factors, clinicians can accurately diagnose ADPKD and implement appropriate management strategies to slow disease progression and improve patient outcomes.