Endoscopic description of renal papillary abnormalities in stone disease by flexible ureteroscopy: a proposed classification of severity and type.

INTRODUCTION: The goal of this original work was to describe papillary abnormalities using flexible ureteroscopy into a new classification and to assess their relation with stone composition.

PATIENTS AND METHODS: We performed a prospective monocentric single-operator study aiming to describe various aspects of renal papillae. Data have been prospectively collected during consecutive 164 sequential flexible ureterorenoscopies required for the treatment of renal stones from May 2011 to March 2015. The collected stones have been examined by microscopy and infrared spectrometry. Serum and urine biochemical samples have been systematically analyzed.

RESULTS: A total of 74 patients (45.1 %) had renal papillary abnormalities on at least one papilla, excluding typical Randall's deposits alone. Various abnormalities were reported, some of them being present in the same patient: tip papillary erosions (51.3 %), anchored papillae calculi (47.3 %), subepithelial stones (18.9 %), cryptic papillae (10.8 %), extrophic papillae (9.46 %) and intraductal deposits (2.7 %). Associations between papillary abnormalities and stone types were found. Intraductal deposits were systematically associated with carbonate apatite IVa2 stones and hypocitraturia. A "first step" classification has been established to standardize the description of these papillary abnormalities for future reports and studies.

CONCLUSIONS: This study highlights the necessity of papillary abnormalities description in further multicentric studies and ureteroscopy's reports. The established classification needs multicentric evaluation and validation. The endoscopic observation and knowledge of pathological aspects of the papillae should help to better understand pathogenesis of nephrolithiasis. Medical or surgical treatments of some abnormalities should be also discussed and evaluated to improve the prevention of stone recurrence.