·         Hydronephrosis- Hydronephrosis is the most common cause of a neonatal abdominal mass and often results from PUJ obstruction. Other causes of hydronephrosis include VUJ obstruction, vesicoureteric reflux, bladder outlet obstructionlvalves, etc. Antenatally, hydronephrosis is usually readily identified; however, gross hydronephrosis may be confused with multicystic dysplastic kidney.

 

·         Multicystic dysplastic kidneys- The majority of cases are unilateral; when bilateral the condition is fatal. US features depend upon the subtype. In pattern type ha the kidney is seen as a large paraspinal flank mass. It contains cysts of various sizes, separated by solid tissue. In type hib multiple renal cysts are associated with renal pelvic dilatation. Type ha is the most common. It is thought to be due to interruption to the vascular supply to the ureter resulting in ureteric atresia before 15 weeks gestation.

 

·         Infantile polycystic kidney disease (IPKD)- Autosomal recessive polycystic kidney; the kidneys are enlarged and echogenic due to the presence of multiple small cysts. The cysts are too small to be resolved sonographically. IPKD may be associated with OH and hepatic fibrosis.

 

 

·         Cystic renal dysplasia- Cystic renal dysplasia can be caused by obstruction to urinary drainage. Sonographically the renal parenchyma is abnormally echogenic. In fetal kidneys with evidence of urinary tract obstruction sonographic demonstration of cortical cysts effectively indicates the presence of cystic renal dysplasia. However, the absence of visible cysts does not exclude cystic dysplasia. The kidneys are not usually enlarged.

 

·         Mesoblastic nephroma- Usually unilateral. Sonographically mesoblastic nephroma is seen as a large, solitary, predominantly solid, coarse, echogenic renal mass which may contain cystic areas. It may be associated with PH.

 

·         Heredofamilial cystic dysplasia- Cystic renal dysplasia is an important feature of several familial syndromes.

The Meckel—Gruber syndrome is a recessive inherited condition associated with bilateral non- obstructive multicystic dysplastic kidneys, occipital encephalocele and postaxial polydactyly. Other syndromes associated with non- obstructive renal dysplasia include:

(1) Asphyxiating thoracic dystrophy

(2) Short rib—polydactyly syndrome

(3) Trisomy 13

(4) Holoprosencephaly.

 

·         Nephroblastomatosis- Nephroblastomatosis is the persistence of primitive blastema in an abnormal location and/or abnormal quantity. US reveals bilateral nephromegaly with normal renal echogenicity, but foci of calcification may be present. Nephroblastomatosis may be associated with PH and can occur as a part of a familial condition — Perlman’s syndrome, which includes nephroblastomatosis, fetal ascites, mascrosomia and Wilms’ tumor.

 

·         Adult type polycyctic disease- Autosomal dominant; the disease may be diagnosed in the fetus. Sonography reveals nephromegaly, increased renal echogenicity and renal cysts of varying sizes.

 

 

·         Beckwith-Wiedemann syndrome- This syndrome may be associated with omphalocele (12% of cases) and organomegaly. There is an increased incidence of hemihypertrophy, renal anomalies, Wilms’ tumor and hepatoblastoma.

 

·         Metabolic disorders- Tyrosinemia type I is inherited in an autosomal recessive manner. Symptoms may present acutely or adopt a more chronic form. Presentation is usually in infancy. Sonographic manifestations include nephromegaly and features of cirrhosis. Prenatal diagnosis may be achieved by amniocentesis or chorionic villous sampling. Glycogen storage disease type I and type ha may both present in infancy; nephromegaly is a common feature.

 

·         Asphyxiating- This short limbed osteochondrodysplasia occurs almost exclusively in caucasians. The sonographic features include renal cysts, a narrow thorax, with or without rhizomelic shortening and with or without polydactyly.