Polycystic kidney disease
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Steven C. Campbell, M.D., Ph.D. Contributors: Cafer Zorkun M.D., PhD.
Synonyms and keywords: Polycystic kidney syndrome; polycystic kidney; PKD
Overview
Pathophysiology
Epidemiology & Demographics
Differentiating Polycystic kidney disease from Other Diseases
Polycystic kidney disease natural history|Natural History, Complications & Prognosis]]
Diagnosis
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.
Diagnostic Findings
Autosomal recessive form
USG
- At USG, the kidneys are massively enlarged and diffusely echogenic bilaterally.
- Corticomedullary differentiation is absent.
- High-resolution USG (linear-array transducer, 7.5 mHz or greater) allows visualization of numerous cylindrical cysts in the medulla and cortex, which represent ectatic collecting ducts.
Autosomal dominant form
- Multiple, variably sized cortical and medullary based cysts
- Renomegaly
- Hemorrhagic cysts are often present
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Treatment
Although a cure for PKD is not available, treatment can ease the symptoms and prolong life.
- Pain: Over-the-counter pain medications, such as paracetamol can relieve pain. For most but not all cases of severe pain, surgery to shrink cysts can relieve pain in the back and flanks. However, surgery provides only temporary relief and usually does not slow the disease's progression toward kidney failure.
- Urinary tract infections: Patients with PKD tend to have frequent urinary tract infections, which can be treated with antibiotics. Early treatment is important, because infection can spread from the urinary tract to the cysts in the kidneys. Cyst infections are difficult to treat because many antibiotics do not penetrate into the cysts. However, some antibiotics are effective.
- High blood pressure: Keeping blood pressure under control can slow the effects of PKD. Lifestyle changes and various medications can lower high blood pressure.
- End-stage renal disease: There are two options for replacing kidney functions: dialysis or transplantation. Healthy (non-PKD) kidneys transplanted into PKD patients do not develop cysts.
Pathological Findings
Adult type Polycystic kidney disease
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Resources
The PKD Foundation is the only non-profit organization worldwide dedicated solely to PKD research. Parent of two children with ARPKD blog: www.kidneysandeyes.com
References
- Nauli SM, Zhou J (2004). "Polycystins and mechanosensation in renal and nodal cilia". Bioessays. 26 (8): 844–56. doi:10.1002/bies.20069. PMID 15273987.
- Grantham JJ, Torres VE, Chapman AB; et al. (2006). "Volume progression in polycystic kidney disease". N. Engl. J. Med. 354 (20): 2122–30. doi:10.1056/NEJMoa054341. PMID 16707749.
External links