Invasive Ultrasonography

Abstract

Although ultrasound is basically considered a noninvasive imaging modality, it is also effective for percutaneously guiding fine needles into deep intraabdominal masses, both solid and cystic, for purposes of sampling their contents. The major applications of this technique are in (1) the aspiration of fluid from cystic masses to characterize the fluid, especially to determine whether it is sterile, infected, or contains malignant cells; and (2) the aspiration of cells from solid masses to determine whether they are benign or malignant. In addition, this technique can guide a needle into an obstructed renal collecting system in order to perform antegrade pyelography so as to determine the cause of the obstructed urinary tract. The needle can then be replaced by a catheter to provide temporary drainage of the obstructed urinary tract until definitive therapy is instituted.