Cystic Fetal Kidneys
· Obstructed kidney- Obstructed kidneys or an obstructed upper moiety of a duplex system may mimic renal cysts; with careful attention to detail no confusion should normally arise.
· Infantile polycystic disease- In this autosomal recessive polycystic kidney disease, large echogenic kidneys are seen. The cysts are usually too small to be resolved sonographically; however very small cysts are occasionally visible with modern scanners.
· Adult type polycystic disease- This autosomal dominant disease has now been reported in the fetus, newborns and juveniles as well as adults. Sonography reveals increased echogenicity in enlarged kidneys (85%) and renal cysts of varying sizes (58%). cysts can be visualized in utero in some cases.
· Multicystic dysplastic kidneys- These are common and are seen as enlarged cystic kidneys. These kidneys do not function. If bilateral, it is a lethal abnormality.
· Cystic renal dysplasia- Caused by obstruction to urinary drainage, most frequently of the urethra but also at the level of the PUJ. In fetal kidneys with evidence of urinary tract obstruction US demonstration of cortical cysts effectively indicates the presence of cystic renal dysplasia as early as 21 weeks gestation. However, the absence of visible cysts does not exclude cystic dysplasia.
· Cystic renal Tumors- Mesoblastic nephroma is the most common congenital renal neoplasm. It is a solitary hamartoma, usually benign. Sonographically mesoblastic nephroma is seen as a complex mass which may contain cystic areas. It may be associated with PH. Wilms’ tumor may also present as a multiloculated mass.
· Heredofamilial cystic dysplasia- Cystic renal dysplasia is an important feature of several familial syndromes. Renal cysts have been described in association with over 50 syndromes. These include the trisomies, von Hippel—Lindau disease, Jeune’s asphyxiating thoracic dystrophy, Meckel—Gruber syndrome, short rib—polydactyly syndrome, Beckwith—Wiedemann syndrome and holoprosencephaly.
· Medullary cyst disease- This condition is characterized by cysts within the renal medulla which may result in tubular atrophy and subsequent renal failure. It usually manifests itself in the adult but is rarely seen in the newborn, with similar pathological findings.