Adrenal hypertrophy: possible pitfall in the sonographic diagnosis of renal agenesis.

Six cases are presented in which the sonographic appearance of adrenal enlargement in the fetus or neonate mimics that of renal tissue. When normal renal tissue is not present, the adrenal preserves its characteristic echogenic medulla and anechoic cortex but enlarges, loses its characteristic "V" or "Y" shape, and appears more elliptical on ultrasound scans. The average length of the adrenal was 3.4 cm on the right and 2.9 cm on the left in these cases, with adrenal thickness increased to an average of 5 mm. Care must be taken not to mistake the enlarged adrenal for renal tissue. Conversely, an elongated adrenal gland without adjacent renal tissue does not necessarily imply renal agenesis, but may occur with renal ectopia.