Sonographic sliding sign in localization of right upper quadrant mass.

Sonographic sliding sign is the observation of dynamic motion of a mass against adjacent organs during respiratory movement or extrinsic pressure. We applied this sign for prospective study in nine patients, each of whom had a large posterior right upper abdominal mass arising from the liver, kidney, or adrenal gland. The sign was found to be very reliable as a criterion for the localization of the origin of the mass in all patients except in the following two cases: a Wilm's tumor that invaded the retroperitoneum and posterior abdominal wall was regarded as a retroperitoneal tumor invading the kidney; and in the other one, an adrenal pheochromocytoma, the sliding sign against the liver and the right kidney was equivocal. In conclusion, judicious use of the sonographic sliding sign will greatly assist in the localization of a large right upper abdominal mass, especially when there is a paucity or lack of retroperitoneal fat.