Sir.—May I comment on the Wilms tumor aspect of the September 1975 review article in the Journal on abdominal ultrasonography (129:1096, 1975). A majority of these tumors can be diagnosed successfully with modern techniques of intravenous urography. Simple serous cysts are extremely rare in children, and the first diagnosis of any intrarenal lesion should be nephroblastoma. In doubtful cases arteriography can be extremely helpful,1 particularly in the late-presenting case that may show nonfunction.
Ultrasonography presents an attractive noninvasive technique for confirming the diagnosis of this condition, but we must be cautious about how we interpret the appearances of the apparently transonic tumor. A nephroblastoma may be so homogeneous and avascular that it presents no internal barriers of impedance and appears to be a transonic or anechoic mass, no matter how the amplitude of the sound is varied. We recently had a case of an avascular tumor in a