Approach Considerations
Ultrasonography is the procedure of choice in the workup of patients with autosomal dominant polycystic kidney disease (ADPKD). It is also ideal for screening patients' family members. [5] Computed tomography (CT), magnetic resonance imaging (MRI), and magnetic resonance angiography (MRA) are useful in selected cases. [21]
Blood pressure should be monitored, to detect early onset of hypertension. Ambulatory blood pressure monitoring may be appropriate.
Other studies to perform include those for chronic kidney disease, as follows:
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Complete blood cell count
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Measurement of blood lipid concentrations,
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Urine studies for albuminuria or proteinuria
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Urine culture
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Uric acid determination
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Intact parathyroid hormone and vitamin D assays
An increased hematocrit may result from increased erythropoietin secretion from cysts. A decrease in urine-concentrating ability is an early manifestation of the disease. Microalbuminuria occurs in 35% of patients with ADPKD. However, nephrotic-range proteinuria is uncommon.
Urinary proteomic biomarkers may have the potential for assessing prognosis in patients with ADPKD but are not available in clinical practice.
Screening for intracranial aneurysm
Intracranial aneurysms are at least twice as common in patients with ADPKD as in the general population. On screening, intracranial aneurysms are found in approximately 10% of asymptomatic patients with ADPKD. [7, 26, 29]
Indications for screening, which is done with head MRI without gadolinium enhancement or CT angiography, include the following [5] :
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Family history of stroke or intracranial aneurysm or hemorrhage; patients with a family history of intracranial aneurysm but a negative screening study should be rescreened at 5–10-year intervals
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Before major elective surgery
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Central nervous system signs or symptoms (eg, nausea and vomiting, lethargy, photophobia, focal signs, seizure, transient ischemic attack, loss of consciousness)
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High-risk occupation, or hobby in which a loss of consciousness may be lethal (eg, airline pilot)
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New-onset severe headache
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Patient anxiety despite adequate information
Cardiac testing
Echocardiography or cardiac MRI, to asses for valvular heart disease, mitral valve prolapse, aortic dilatation, or congenital abnormalities.
Genetic testing
Genetic testing is not part of regular clinical practice, but may be performed selectively. [5] .Genetic testing can accurately differentiate ADPKD, autosomal recessive polycystic kidney disease (ARPKD), and autosomal dominant polycystic liver disease (ADPLD). In ADPKD, the presence of either PKD1 or PKD2 subtypes changes the prognosis and may help guide clinical management. [20, 17]
Genetic counseling
To inform affect individuals and their related family members about diagnosis, prognosis, and treatment.
Ultrasonography
Ultrasonography is the most widely used imaging technique to help diagnose ADPKD. It can detect cysts from 1-1.5 cm. This study avoids the use of radiation or contrast material, is widely available, and is inexpensive. The sensitivity of ultrasonography for PKD1 phenotype is 99% for at-risk patients older than 20 years; however, false-negative results are more common in younger patients. Sensitivity for PKD2 phenotype is lower and is still not well defined.
Ultrasonography is also useful for exploring abdominal extrarenal features of ADPKD (eg, liver cysts, pancreatic cysts).The presence of hepatic or pancreatic cysts supports the diagnosis of ADPKD.
Ultrasonographic diagnostic criteria for ADPKD in patients with mutations in PKD1 were established by Ravine et al in 1994 and are as follows [6] :
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At least 2 cysts in 1 kidney or 1 cyst in each kidney in an at-risk patient younger than 30 years
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At least 2 cysts in each kidney in an at-risk patient aged 30-59 years
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At least 4 cysts in each kidney for an at-risk patient aged 60 years or older
As the Ravine criteria are less sensitive for individuals with mutations in PKD2, Pei et al proposed the following ultrasonographic diagnostic criteria for ADPKD due to either PKD1 or PKD2 mutations, to screen patients with a family history of ADPKD but unknown genotype [4] :
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Three or more kidney cysts (unilateral or bilateral) in patients aged 15 to 39 years
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Two or more cysts in each kidney in patients aged 40 to 59 years
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Four or more cysts in each kidney in patients aged ≥60 years
The presence of fewer than 2 renal cysts provides a negative predictive value of 100% and can be considered sufficient for ruling out disease in at-risk individuals older than 40 years of age. [4]
CT, MRI, and MRA
CT is more sensitive than ultrasonography and can detect cysts as small as 0.5 cm. However, it exposes the patient to radiation and is more expensive; therefore, it is not used routinely for diagnosis or for follow-up studies of ADPKD. CT may be useful in complicated cases (eg, kidney stone, suspected tumor).
MRI is more sensitive than either ultrasonography or CT scanning. It may be more helpful in distinguishing renal cell carcinoma from simple cysts.
MRI is the best imaging tool for monitoring kidney size before starting tolvaptan treatment, and it is the criterion standard to help determine kidney volume for clinical trials of drugs for ADPKD. However, it is not routinely used because it is expensive and tedious. It should not be used unless the patient is in a protocol or similar situation.
Spithoven et al reported that determining measured total kidney volume (TKV) by MRI and manual tracing took an average of 55 minutes, but a newer proposed MRI method for estimating TKV, eTKV ellipsoid, required an average of only 5 minutes. In their comparison study, eTKV ellipsoid performed relatively well compared with mTKV and could detect change in TKV over time. [30]
Magnetic resonance angiography (MRA) is the preferred imaging technique for diagnosing intracranial aneurysms (ICAs). It is used selectively rather than routinely. Indications for this study are as follows [7] :
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Family history of stroke or intracranial aneurysm or hemorrhage; patients with a family history of ICA and a negative screening study should be rescreened at 5-10–year intervals.
-
Before major elective surgery
-
Central nervous system signs or symptoms (eg, nausea and vomiting, lethargy, photophobia, focal signs, seizure, transient ischemic attack, loss of consciousness)
-
High-risk occupation, or hobby in which a loss of consciousness may be lethal (eg, airline pilot)
-
New-onset severe headache
-
Patient anxiety despite adequate information
Laboratory Studies
Laboratory studies in patients with ADPK are largely performed to assess for chronic kidney disease, and include the following:
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Complete blood cell count
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Kidney function: Creatinine, estimated glomerular filtration rate
-
Measurement of blood lipid concentrations
-
Urine studies for albuminuria or proteinuria
-
Urine culture
-
Uric acid determination
-
Intact parathyroid hormone and vitamine D assay
An increased hematocrit may result from increased erythropoietin secretion from cysts. A decrease in urine-concentrating ability is an early manifestation of the disease. Microalbuminuria occurs in 35% of patients with ADPKD, most of them in the context of hypertension. However, nephrotic-range proteinuria is uncommon.
Genetic Testing
Genetic testing for ADPKD patients is not part of routine clinical practice. Molecular genetic testing approaches can include a multigene panel or genomic testing (exome or genome sequencing), depending on the phenotype. A multigene panel including PKD1, PKD2, ALG5,ALG9, DNAJB11, GANAB, IFT140 and other genes of interest (see differential diagnosis) is most likely to identify the genetic cause of the disease. [31]
Situations in which genetic testing is appropriate include the following [5, 27] :
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When a definitive diagnosis is required in young individuals, such as a potential living-related organ donor in an affected family with no clear imaging information
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In patients with a negative family history of ADPKD in whom alternative causes of cystic kidney disease are considered
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In couples requesting genetic counselling and family planning advice
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In cases of marked clinical discordance, such as very early onset disease or very mild disease, where knowledge of the pathogenic variant may provide an explanation or prognostic information
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Polycystic kidney.
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Polycystic kidney disease and massive polycystic liver disease.
