V6-01: INTRODUCTION OF A RENAL PAPILLARY GRADING SYSTEM FOR PATIENTS WITH NEPHROLITHIASIS
An often overlooked finding at the time of renal endoscopy for patients with nephrolithiasis is the appearance of the renal papillae. Recent work has demonstrated that it is possible to distinguish specific stone forming phenotypes by endoscopic patterns of papillary appearance alone. These variable expressions are likely to have clinical significance, yet the ability to pursue such research efforts remains limited by the lack of a standardized system to describe findings. In this video, we introduce a novel grading system designed to standardize and simplify the description of the papillae among stone formers at the time of endoscopy.
Since 1999, over 300 patients have been prospectively enrolled and given consent to be part of an NIH funded project studying the pathogenesis of stone formation at a single institution. Patients have been treated and studied using both percutaneous and retrograde ureteroscopic approaches. Detailed renal mapping is performed in each case using a combination of fluoroscopy to define the anatomy and high definition digital nephroscopy to study the papillae. A grading system was developed based upon consensus opinion and collective knowledge and expertise of the primary research team. The grading system comprises four recurring abnormal papillary features (plugging, pitting, loss of contour, amount of Randall's plaque). Upon papillary inspection each papilla receives a numerical grade from 0-2 reflecting the severity of disease for each measured domain. Scores are then added to create a sum total. Validation of the system was performed by independent review and grading of video clips demonstrating 50 unique papillae from separate kidneys by four separate urologists. All papillae were scored in a randomized and blinded fashion and with repetition. Weighted kappa statistics were determined to describe intra and inter-observer reliability.
Intraobserver reliability was substantial across all domains with all weighted kappa statistics being 0.6 or greater (substantial agreement). Interobserver reliability was similarly substantial for plugging, pitting and loss of contour though moderate for Randall's plaque (0.52).
The creation of a standardized system to describe papillary appearance in stone formers has considerable clinical and academic utility. Future research is needed to further correlate papillary scores to meaningful clinical endpoints.
Funding: NIH PO1 DK56788