According to the clinical experience, many physicians are alerted to the possibility of Polycystic Kidney Disease (PKD) in three different settings: when someone reports that there is a family history of PKD; when there are signs and symptoms that commonly occur in PKD; or when a test is done for some other reason and cysts are found in the kidney.
At present, there are three main clinical tests that can be used to diagnose
a person with PKD: ultrasound, computed tomography (CT) or magnetic resonance
1, ultrasound is the most common and least costly screening method for PKD. A
recent research study has produced diagnostic criteria that are useful for
testing individuals having either the PKD1 or PKD2 mutation in the usual
clinical setting in which molecular genotyping is seldom performed.
2, computed tomography (CT) and MRI scans are likely to be more sensitive
than ultrasound but the sensitivity of these methods have not been
systematically analyzed yet. CT scans, however, involve radiation and may also
require iodinated contrast dye which can be toxic to the kidneys. CT scans or
MRIs may be indicated for the evaluation of certain complications like bleeding
into a cyst or a suspected kidney stone or alternatively if a more sensitive
screening test with the ability to detect small cysts is deemed necessary.
In addition, DNA testing is also available for ADPKD. There are two types of
DNA tests: Gene linkage testing and Direct Mutation analysis. Gene linkage can
determine PKD status with a 99 percent probability in informative families.
Linkage testing is not a direct analysis of the DNA sequence of the PKD1 and
PKD2 genes. Rather, it relies on the identification of certain “markers” in the
DNA of several members of a family in which PKD has been diagnosed. For linkage
analysis, blood samples must be obtained from the person being tested (the
“proband”) as well as from several (typically three or more including the
proband) persons from more than one generation of the proband's family,
including those affected and unaffected with PKD. A detailed family history and
pedigree are also required. The results are typically reported to all family
members that provided blood samples for the analysis. In contrast, direct DNA
sequencing requires only a single sample from the proband. This method is a
direct analysis of the DNA sequences of the PKD1 and PKD2 genes. It is private,
and the results are only reported to the proband's physician and the patient
(the proband). Using very sophisticated DNA sequencing apparatus, each of the
nearly 17,000 “bases” of DNA are analyzed and the entire sequence is thus
determined. This method is capable of identifying those changes in the sequence
that is indicative of disease. It may be the only option if family members are
unavailable or unwilling to participate in a linkage study. Each of these
methods has pros and cons.