infantile polycystic kidney disease

infantile polycystic kidney disease


symmetrical enlargement of both kidneys results from a defect in the collecting tubules. the primary embryologic anomaly is an alteration in the collecting tubules between the second and third week of gestation. the ureteral bud and metanephric blastema are normal. normal calyces and papillae are formed and allow for normal renal function early in pregnancy. the medullary ectasia produces innumerable 1-2 mm cysts; there is no obstruction and the renal calyces and pelves are normal. cysts develop in bowman’s capsules, nephrons, or part of the collecting tubules. there may be involvement of hepatic structures, with elongation and dilatation of the bile ducts. ipkd is divided into four groups: perinatal, neonatal, infantile and juvenile, dependent on age of onset. the perinatal form is the most common, with massive kidneys in 90% and renal failure in utero or during the neonatal period. death usually occurs from pulmonary hypoplasia, a result of the oligohydramnios. the later the onset of the disease, the smaller the kidneys, and the slower the progress of renal disease. there is also onset of liver involvement. the condition is always bilateral. in the late-onset form it affects 1/40,000-60,000 newborns and follows an autosomal recessive pattern of inheritance. ultrasounds of parental kidneys are normal.


this diagnosis should be considered when there is enlargement of the kidneys bilaterally without identifiable cysts, no identifiable obstruction, and decreased fluid or oligohydramnios. the condition may be seen as early as 48-50 days gestation, but is usually diagnosed after 16 weeks. prior to 16 weeks there may be some production of amniotic fluid and the specific diagnosis may be more difficult. the kidney to abdomen ratio is greater than 0.27 to 0.30. a midtrimester diagnosis usually includes oligohydramnios and subsequent pulmonary hypoplasia, which makes it a lethal condition. if identified later in pregnancy, the kidneys may become large enough to result in loss of abdominal muscle tone. also, cysts may become large enough to identify individually. over the course of a continuing pregnancy, the kidneys will continue to enlarge and some signs of liver disease (i.e., enlarged bile ducts) may be seen. oligohydramnios will lead to the symptoms of potter’s syndrome (unusual facies, contractures, loose skin). obstetric management should include serial ultrasound evaluations; if there is significant increase in abdominal girth, one must consider the best route for delivery. there is a high risk for stillbirth and pulmonary hypoplasia. ipkd is lethal during the neonatal period in about 80%. since there can be intra-family variability in expression, siblings should be evaluated for mild symptoms like renal insufficiency or childhood hepatic fibrosis. any family history of these problems in siblings can help make the diagnosis prenatally. it also means that a family history of ipkd in a previous pregnancy will not always lead to the identification of the same severe findings in a subsequent affected pregnancy.

differential diagnosis

babies with meckel-gruber syndrome also have enlarged kidneys and oligohydramnios, although the cysts are more likely to be large enough to be identified and the associated, encephalocele and polydactyly, may be seen. an obstructive condition such as posterior urethral valve syndrome or ureteral pelvic junction may also produce large kidneys and lack of fluid, although the renal pelves and calyces are usually affected as well. multicystic, dysplastic kidneys generally have large cysts which also produce an abnormal pelvocalycele system. tumours – wilms tumour also produces enlarged solid-appearing kidneys, but is usually unilateral (90%) and usually does not cause oligohydramnios. syndromes other than ipkd associated with diffuse micro or dysplastic cystic kidneys; (examples are included in the associated syndrome list) associated syndromes: ipkd is a syndrome and is not associated with other syndromes. however, similar renal findings on ultrasound may be associated with syndromes listed under microcystic, echodense, or dysplastic kidneys

sonographic features

diagnosable after 16 weeks, although onset of kidney enlargement varies

oligohydramnios may lead to potterís features – characteristic facies, redundant skin, limb contractures

bilateral enlarged kidneys, normal shape, increased echogenicity, progressive

renal cortex may be echogenic early in pregnancy with hypoechoic medulla

numerous microscopic cysts result in characteristic renal echogenicity, some may becoming large enough to be seen individually

decreased to absent urine in the bladder (nonvisualised bladder)

small fetal thorax in severe cases

associated syndromes


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