Ultrasound of renal sinus: new observations.

Technical factors and diagnostic criteria that permit discrimination among diseases of the renal sinus are described. Because the size of the collecting system changes with the state of hydration, a standard approach permits optimal comparison of examinations performed on different occasions. A fluid challenge is indicated if relative or partial obstruction is suspected. Ureteric compression permits optimal delineation of the collecting system but is indicated only in selected situations. Both tumor and blood clot within the renal sinus appear as echogenic masses without a significant acoustic shadow. Serial ultrasound studies demonstrate the resolution of the blood clot. Both in vivo and in vitro studies of renal stones demonstrate that the acoustic shadow of nephrolithiasis is best seen with low gain and with the stone within the focal zone of the transducer.