It is now accepted that previous terms such as Infantile Polycystic Kidney Disease (PKD), Early Childhood PKD, Late Childhood PKD, Adolescent PKD, Juvenile PKD, Early Onset PKD and Adult PKD are incorrect. Since the genetic causes of polycystic kidney disease are now known, it is correct to say that a person has Autosomal Recessive Polycystic Kidney Disease (ARPKD) or Autosomal Dominant Polycystic Kidney Disease (ADPKD), or some other form of cystic kidney disease.
Fetal ultrasound may visualize large echogenic kidneys, also described as “bright”, from 13 weeks gestation, with low or absent amniotic fluid (oligohydramnios) beginning after 20 weeks gestation. There are however many instances where ARPKD is not visualized on sonogram until the 3rd trimester or after birth. A prenatal finding may also include absence of fetal bladder filling, although this finding does not always correlate with postnatal severity. Huge flank areas may complicate vaginal delivery. For those infants that are severely affected, Potter’ facies or Potter’s syndrome may be present. This is seen as deep set eyes, broad, flattened nose, abnormally small jaw bones, and low set ears; additionally, deformities of the extremities due to fetal restriction and compression caused by insufficient amniotic fluid occurs.
Kidneys can be grossly enlarged, their size peaking at 1 to 2 years of age, with stabilization at 4 to 5 years of age. With time, sonographic patterns change due to the progression of cysts and fibrosis, changing the typical kidney shape.
Older patients may be mistakenly identified as having ADPKD. Contrast- enhanced computerized tomography (CT) has been effective in visualizing the collecting tubules, which are dilated in ARPKD. Ultrasounds have largely replaced intravenous pyelograms (IVP). Glomerular Filtration Rate (GFR) may improve during the first 6 months of life from kidney maturation. Approximately a third of the ARPKD population will need dialysis or kidney transplant by 10 years of age. However the decline in renal function is very variable and in some cases of ARPKD end stage renal failure (ESRF) does not occur until adulthood.
Amniocentesis and direct genetic testing cannot yet offer an ARPKD diagnosis. Prenatal testing is available for families who have had one confirmed ARPKD birth. This is an indirect diagnostic technique, based on gene linkage and the PKHD1 locus, and dependant on DNA from current or previously affected children and their parents. Diagnosis should be differentiated from other kidney disorders, including ADPKD, cystic dysplastic kidneys, glomerulocystic kidney disease, and medullary sponge kidney.