Polycystic kidney disease laboratory tests
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aarti Narayan, M.B.B.S [2]
Overview
Laboratory tests
Blood tests
- Increased hematocrit from increased erythropoetin secretion from the cysts
- Decreased serum calcium levels
- Increased serum phosphate levels
- Increased parathyroid hormone levels
- Nephrogenic diabetes insipidus: Increased ADH levels with low urine osmolarity
Urinalysis
Urine culture
- May show growth of organisms if symptoms of urinary tract infection are present
Genetic testing
- A definite diagnosis of ADPKD relies on imaging or molecular genetic testing. The sensitivity of testing is nearly 100% for all patients with ADPKD who are age 30 years or older and for younger patients with PKD1 mutations; these criteria are only 67% sensitive for patients with PKD2 mutations who are younger than age 30 years.
- Large echogenic kidneys without distinct macroscopic cysts in an infant/child at 50% risk for ADPKD are diagnostic.
- In the absence of a family history of ADPKD, the presence of bilateral renal enlargement and cysts, with or without the presence of hepatic cysts, and the absence of other manifestations suggestive of a different renal cystic disease provide presumptive, but not definite, evidence for the diagnosis.
- Molecular genetic testing by linkage analysis or direct mutation screening is available clinically; however, genetic heterogeneity is a significant complication to molecular genetic testing.
- Sometimes a relatively large number of affected family members need to be tested in order to establish which one of the two possible genes is responsible within each family.
- The large size and complexity of PKD1 and PKD2 genes, as well as marked allelic heterogeneity, present obstacles to molecular testing by direct DNA analysis.
- In the research setting, mutation detection rates of 50-75% have been obtained for PKD1 and ~75% for PKD2.
- Clinical testing of the PKD1 and PKD2 genes by direct sequence analysis is now available, with a detection rate for disease-causing mutations of 50-70%.
- Genetic counseling may be helpful for families at risk for polycystic kidney disease.