A new technique for renal biopsy: the transurethral approach.

An 18 gauge needle sheathed in an 8F catheter can be advanced into an upper calix through the lumen of a transurethrally placed 10F catheter and used to biopsy the renal cortex. The transurethral biopsy technique is less painful, less invasive and simpler than the open or laparoscopic approach, and it can be used as an extension of cystoscopic examination to avoid percutaneous biopsy.