Percutaneous and transureteral biopsies of renal papillae: safe and appropriate procedures for in vivo histologic analysis in stone formers.

BACKGROUND AND PURPOSE: According to the Randall plaque theory, urinary crystals may attach to focal interstitial deposits of calcium phosphate (CaP), localized in the tip of the renal papillae. The aim of this prospective study was to evaluate the feasibility and safety of papillary biopsy, performed during ureterorenoscopy (URS) or percutaneous nephrolithotomy (PCNL), to obtain, in vivo, appropriate samples to investigate interstitial CaP deposits that represent Randall's plaques precursors. PATIENTS AND METHODS: Twenty-eight patients who were affected by recurrent renal stones, 13 males and 15 females, with a median age of 42.5 years (range 17-76 y), underwent rigid and/or flexible URS (8 patients) or PCNLs (20 patients). In all cases, endoscopic biopsies from renal papillae were performed. Papillary samples were obtained by means of 3F or 4F cup biopsy forceps if semirigid and flexible ureterorenoscopes were used. During percutaneous procedures, with rigid and flexible instruments, 5F or 10F cup forceps were used. The same pathologist analyzed all the histologic specimens. RESULTS: All patients underwent successful biopsy procedures. The quality of the obtained tissue allowed for an accurate histochemical analysis in 27 of 28 (96.4%) biopsies. One biopsy was inadequate because of some important regressive phenomena. No specific complications had to be attributed to biopsy procedures. CONCLUSIONS: Percutaneous or transureteral biopsies of renal papillae resulted in being safe and appropriate procedures to obtain papillary samples to identify the presence of interstitial calcium deposits. In the light of the low number of inadequate biopsies, it can be concluded that no difference was found between the percutaneous and transureteral bioptic approach.