A 34-year-old primigravida was referred for sonography in her 26th week of pregnancy to rule out fetal anomalies. Fetal biometry corresponded to 26 weeks. The following image of the renal area were obtained.

An axial scan at the level of the lower pole of the kidney demonstrate cysts of multicystic dysplastic left kidney and lower pole of right kidney anterior to aorta and inferior vena cava (Adr = adrenal gland).

A coronal scan at a lower level showed cysts of multicystic dysplastic left kidney crossing the midline (A&I = aorta and inferior vena cava) and extending up to lower pole of right kidney.  These features are diagnostic of Horseshoe kidney with unilateral multicystic dysplasia  on left side.

The axial scan of fetal abdomen showed multicystic dysplasia of left kidney.

A coronal scan of right kidney showed the right adrenal lengthened and flattened, indicating that right kidney is low placed.

The child was delivered normally at term. Postnatal Scan was done at 4 months of age, which confirmed the prenatal diagnosis.

Many recognized the multicystic kidney and assumed that there was another anomaly of the contralateral kidney (agenesis was popular). But if that had been the case there would have been no amniotic fluid. Thus some functioning kidney had to be present somewhere.