Ultrasound is very useful in differentiating solid from cystic masses. Cystic masses, such as a kidney with hydronephrosis, show up on an ultrasound as large black areas in the kidney. Solid masses, such as a kidney tumor, appear as heterogeneous, echogenic masses.
Shortly after birth, this infant was found to have a right upper quadrant mass. This ultrasound shows a large solid tumor in the lower pole of the kidney. Notice how many echoes are generated by the mass (it is light gray). You can see a slightly dilated renal pelvis at the upper pole of the kidney. The tumor obstructed the ureter causing hydronephrosis. This is a mesoblastic nephroma. They are almost always benign. The tumor was removed and the girl is doing well.
Ultrasound is the first line imaging study in children with abdominal masses because most such masses are cystic. Once the ultrasound showed a solid mass, a CAT scan was obtained to determine the extent of the tumor and to detect any possible abdominal metastases.
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© David A. Hatch, M.D., 1996