[Ultrasound study of congenital mesoblastic nephroma].

The mesoblastic nephroma is the most common renal tumor among newborn and young infants. The tumor is benign, and metastatic growth has only been described in individual cases. Three patients suffering from histologically proven mesoblastic nephroma were examined with an ultrasonic device. Sonographically, the mesoblastic nephroma is manifest as solid and homogeneous tumor of a fine to medium coarse basic texture and of a medium echogenity which may show individual small cystic areas. The tumor cannot be delimited sharply from the healthy renal tissue although uneventful tissue which often caps the kidney is proved. A secure differential diagnosis against a Wilms' tumor is not possible if metastases cannot be detected sonographically or by means of an excretory urogram. The echopattern and the relation of the mesoblastic nephroma to the kidney in combination with an excretory urogram should, however, make the delimitation of a neuroblastoma possible.