adult polycystic kidney disease
description
[potterís type iii polycystic kidney, autosomal dominant polycystic kidney disease and adult hepatorenal polycystic disease] adult polycystic kidney disease is one of the most common genetic disorders, and the third most prevalent cause of chronic renal failure. estimates of frequency based on hospital admissions are of the order of 1 in 3,500, whereas frequency among autopsies range between 1 in 1,000 and 1 in 300-400. dalgaard (1957) estimated the risk of developing the disease up to age 80 as about 1 in 1,200. clinically the onset is typically in the third or fourth decade, but infantile and neonatal cases have been reported. unilateral presentation of adult type polycystic disease has been reported in children. in potterís type iii kidneys the defect appears to be at the level of the ampulla but involvement is not universal and some ampullae are normal. the cysts correspond to both dilated collecting ducts and other tubular portions of the nephron with a mixture of normal and abnormal elements. massive enlargement of renal tubules to form cysts may be the result of increased proliferation of renal tubular epithelial cells in some nephrons. involvement of the liver is less prominent than in infantile polycystic kidney disease. the lesions consist of periportal fibrosis and may be focal. apkd is inherited as an autosomal dominant trait with a 50% recurrence risk, and the genetic locus for the disorder is located on chromosome 16.
diagnosis
prenatal diagnosis of apkd is available using gene linkage analysis of chorionic villus sampling or amniotic fluid cells. however, gene linkage studies do not predict the natural history of apkd in the fetus. linkage studies are available in those families where a diagnosis of apkd has been made. if a diagnosis has been made in a fetus, serial ultrasonography can be offered to exclude early or severe in utero development of cystic disease. if cystic or solid enlarged kidneys are detected, especially in association with normal amniotic fluid volume, early onset apkd should be considered in the differential diagnosis. a unilateral enlarged echogenic kidney, or kidney with multiple small cysts can be compatible with this diagnosis with later development of similar findings in the other kidney. both parents should be offered renal ultrasound evaluation to rule out apkd, and if the diagnosis is suggested, linkage studies can be made available. while amniotic fluid volume may be normal earlier in pregnancy, it may decrease later in the pregnancy. fetal ascites and non-immune hydrops may be associated findings.
differential diagnosis
one-third of babies with trisomy 13 or 18 have renal microcysts, but there are usually other findings such as central nervous system, facial and skeletal anomalies. 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 anomalies, 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 pelvocalyceal system. tumours such as wilms’ tumour also produce enlarged solid-appearing kidneys. wilmsí tumours are usually unilateral (90%) and usually do not cause oligohydramnios even later in the pregnancy. the sonographic appearance may be similar to that of ipkd but the amniotic fluid volume may remain normal longer or even throughout pregnancy. if the initial involvement is unilateral, apkd should be seriously considered.
sonographic features
rarely presents prenatally, earliest diagnosis 23.5 weeks, several third trimester diagnoses
bilaterally enlarged echogenic kidneys or multiple small cysts
echogenicity or cysts may be more prominent in one kidney, may appear unilateral initially
amniotic fluid volume usually normal
ascites and hydrops reported as associated findings
associated syndromes
references
- porch p, et al unilateral presentation of adult type polycystic kidney disease in children j urology 135:744-746
- romero r, pilu, g, jeanty p, ghidini a, hobbins jin: prenatal diagnosis of congenital anomalies appleton & lange: norwalk, p268-270
- dalgaard, oz bilateral polycystic disease of the kidneys acta med scand 158:1-251
- pretorius dh et al diagnosis of autosomal dominant polycystic kidney disease in utero and in the young infant j ultrasound med, 6:249