Login to Access Video or Poster Abstract: MP19-08
Sources of Funding: None

Introduction

A renal papillary grading scale (PGS) was recently introduced to standardize the description of papillary pathology during endoscopy. Application of this system to patients with variable stone compositions has yet to be described. Idiopathic calcium oxalate (CaOxSF) and calcium phosphate stone formers (CaPSF) are known to have unique papillary appearances but there is currently no tool to reliably quantify these differences. We tested the hypothesis that the PGS could reliably distinguish these two stone forming phenotypes.

Methods

5-10 second video clips of individual papillae were created from previously recorded endoscopic stone removal procedures performed on metabolically confirmed CaOxSF and CaPSFs. Clips were graded 3 times each by 4 blinded investigators (3 urologists, 1 basic scientist) in a random order and with rotated orientations (108 videos/grader). The PGS measured papillary pathology across 4 domains including ductal plugging, pitting, loss of contour, and Randall's plaque. Features were graded (0-2) on severity of expression. Sum totals were calculated to account for total papillary pathology (range 0-8). Weighted Kappa (&[kappa]) scores were calculated to assess intra- and inter-observer reliability. Papillary scores between stone type were compared.

Results

Intra-observer reliability was substantial to near perfect on all domains (&[kappa] ranging from 0.75-0.99). Inter-observer reliability was near perfect for ductal plugging (&[kappa]=0.84), substantial for Randall's plaque (&[kappa]=0.68), moderate for pitting (&[kappa]=0.56), and fair for loss of contour (&[kappa] =0.40). All domains had highly significant score differences (p<0.001) between the CaOx and CaP groups. CaOxSFs had higher amounts of Randall's plaque while CaPSFs had a higher degree of ductal plugging (p<0.01) (Figures 1, 2).

Conclusions

Papillary appearance can be reliably measured and differs between CaOxSFs and CaPSFs using the PGS. Incorporation of this tool at the time of endoscopy has potential to improve the ability to classify patients with nephrolithiasis.

Funding

None