The diagnosis of polycystic kidney disease depends upon the clinical findings and the imaging results.
Clinical presentation of autosomal recessive PKD
In the autosomal recessive form of polycystic kidney disease (ARPKD), the symptoms are present at birth or may develop in early infancy or in childhood. Rarely, the presentation is delayed to adulthood.
VIDEO ARPKD in fetal life
Ultrasound findings in a fetus with ARPKD include:
Diffusely echogenic kidneys
Reduced amniotic fluid volume
Empty urinary bladder in some cases
ARPKD at birth
Typical symptoms include respiratory difficulty at birth with a grossly enlarged abdomen.
Abdominal imaging reveals the presence of bilaterally enlarged, echogenic kidneys.
Additional diagnostic features include:
Biliary duct atresia
Congenital hepatic fibrosis signaled by enlargement of the liver and spleen or the presence of esophageal varices
No evidence of PKD in either biological parent
Family history of ARPKD in a sibling established by histologic or genetic diagnosis
ARPKD in infancy
In infants, the diagnosis is based on clinical features and imaging findings such as:
Palpable masses in the flank on both sides
History of chronic lung infections or other lung symptoms which have not been diagnosed
History of low amniotic fluid volume
History of spontaneous pneumothorax in the immediate neonatal period
Presence of hypertension
Biliary duct ectasia
Congenital hepatic fibrosis
ARPKD in childhood and later
In children or young adults, clinical features and imaging results which are strongly suggestive of ARPKD include:
Bilaterally echogenic kidneys, enlarged, normal or small in size (due to progressive fibrosis)
Signs and symptoms of portal hypertension
Bleeding from esophageal varices
Genetic testing in ARPKD
Various methods of molecular genetic testing are available to detect mutations in the PKHD1 gene, such as:
Targeted mutation analysis
Deletion/duplication analysis using various polymerase chain reaction (PCR) techniques or probe amplification methods
Linkage analysis if the family is available and willing to be tested.
The place of molecular genetic testing is when clinical features are not diagnostic but suspicion exists as to the condition.
Pre-implantation genetic testing is used by certain couples who wish to rule out the presence of the mutation already identified in their genes, in their offspring.
Clinical presentation of autosomal dominant PKD
Autosomal dominant PKD (ADPKD) often presents with a positive family history for the disease, and enlargement of the kidneys and the liver. The diagnosis is based upon the ultrasound findings.
Ultrasound findings in ADPKD
With a 50% risk for ADPKD, the characteristic findings on ultrasound include:
Three or more cysts in the age group of 15-39 years
Two or more cysts per kidney in the age group 40-59 years
Enlargement and diffuse echoes without cysts in a young child
Renal cysts bilaterally
Cysts in the liver or pancreas most commonly but also in the seminal vesicles or arachnoid membrane
Extrarenal findings may be present, such as
Aortic root dilatation
Thoracic aortic dissection
Mitral valve prolapse
Abdominal wall hernias
Molecular genetic testing
Molecular genetic testing in the form of sequence analysis, or duplication/deletion analysis, of the PK1 and PKD2 genes, is often required for a definitive diagnosis if:
the imaging tests are not conclusive
the family history is negative for ADPKD
the clinical features are more mild or intense than usual
atypical clinical features are present
there is a suspicion of another condition causing renal cysts
Screening for ADPKD
Once the gene variant responsible for the disease in a family is identified, it may be used for presymptomatic genetic diagnosis in:
Other family members with suspicious imaging results
Younger relatives who need a conclusive diagnosis because imaging is not reliable for the diagnosis of ADPKD before 30 years
Ultrasound or other imaging techniques are used to exclude ADPKD before living kidney donation from a related donor at risk for the disease.
The pattern of disease severity within a family line may help predict how much it will affect other members with the condition. The severity may vary depending on the genetic variability, the type of mutant gene and environmental factors.
Imaging techniques in PKD
Abdominal ultrasound examination with a high-resolution probe capable of picking up 1-2 cm cysts is usually preferred as the first choice for diagnosis, because of its:
Avoidance of ionizing radiation or contrast agents
Detailed accurate visualization
Other imaging techniques used to diagnose PKD include
Magnetic resonance imaging (MRI) when ultrasound results are not definitive
Computerized tomography scanning
Magnetic resonance cholangiopancreatography (MRCP), which delineates the biliary ducts more clearly and may obviate the need for liver biopsy