"Faceless kidney": CT sign of renal duplicity.

A CT sign of renal duplicity is described. In kidneys with either bifid renal pelvis or complete duplication of the collecting system, a transverse CT section obtained at the mid pole or junction of the fused upper and lower pole cortical moieties may reveal a "faceless" renal appearance lacking vascular or collecting system elements. Recognition of this finding allows a correct diagnosis of partial or complete duplication of the renal collecting system and prevents a false impression of an intrarenal mass lesion.