What are the recommendations for testing and managing polycystic kidney disease (PKD) in adults?

Testing for Polycystic Kidney Disease in Adults

Abdominal ultrasound is the recommended first-line imaging test for screening adults at risk for autosomal dominant polycystic kidney disease (ADPKD), with age-specific diagnostic criteria to confirm or exclude the diagnosis. 1

Diagnostic Approach for Adults with Suspected ADPKD

Adults with Positive Family History

1. Initial Screening: Abdominal Ultrasound

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

2. If ultrasound findings are equivocal or atypical:

   • Proceed to MRI or CT imaging
   • MRI criteria (ages 16-40 years): >10 cysts total confirms ADPKD; <5 cysts total rules out ADPKD 1

3. Genetic Testing - Consider when:

   • Equivocal imaging results
   • Atypical extrarenal features
   • Additional prognostic information is needed
   • Family planning considerations
   • Young living-related kidney donors (age <30 years) 1, 3

Adults with Incidentally Detected Kidney/Liver Cysts (No Known Family History)

1. For multiple cysts or atypical presentation:

   • Perform kidney MRI or CT
   • Consider genetic testing if ADPKD is suspected 1

2. For solitary cysts:

   • Follow-up imaging is recommended
   • Genetic testing is not recommended for patients with a single cyst, no extrarenal findings, and negative family history 1

Prognostic Assessment

After diagnosis, prognostic assessment is important for treatment planning:

1. Mayo Imaging Classification (MIC):

   • Uses height-adjusted total kidney volume adjusted for age
   • Stratifies patients with typical imaging into 5 groups (1A-1E), indicating accelerating decline in kidney function
   • Measured most accurately by MRI or CT scan 1

2. Genetic factors affecting prognosis:

   • PKD1 mutations cause more severe disease than PKD2
   • Truncating PKD1 mutations cause more severe disease than non-truncating mutations
   • Male sex is associated with more severe disease 1, 3

Special Considerations

• Genetic testing approach: When genetic testing is indicated, a multigene panel that adequately covers PKD1 is preferred over testing single genes 1

• Family counseling: Families should be encouraged to discuss the disease and genetic risks openly with children in an age-appropriate manner 1

• Screening intervals: If initial ultrasound is normal in an at-risk individual, rescreening is not necessary at intervals shorter than 3 years 1

Pitfalls to Avoid

1. Misdiagnosis in young individuals: The negative predictive value of a normal ultrasound in childhood is limited, as cysts develop gradually over time 1

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

3. Inadequate genetic testing: PKD1 is technically challenging to sequence due to its large size and presence of pseudogenes; ensure testing is performed at a laboratory with expertise in ADPKD genetics 3

4. Delayed prognostic assessment: Early assessment of disease severity is important as potential therapies are being developed that may slow cyst growth 4

By following this structured approach to testing, ADPKD can be accurately diagnosed in adults, allowing for appropriate monitoring and management to minimize morbidity and mortality related to this progressive condition.