Endoscopic Evidence That Randall's Plaque is Associated with Surface Erosion of the Renal Papilla

Abstract

Objective: This study was conducted to assess the reliability and precision of an endoscopic grading scale to identify renal papillary abnormalities across a spectrum of equipment, locations, graders, and patients. Materials and Methods: Intra-and interobserver reliability of the papillary grading system was assessed using weighted kappa scoring among 4 graders reviewing a single renal papilla from 50 separate patients on 2 occasions. Grading was then applied to a cohort of patients undergoing endoscopic stone removal procedures at two centers. Patient factors were compared with papillary scores on the level of the papilla, kidney, and patient. Results: Graders achieved substantial (kappa >0.6) intra-and inter-rater reliability in scored domains of ductal plugging, surface pitting, and loss of contour. Agreement for Randall's Plaque (RP) was moderate. Papillary scoring was then performed for 76 patients (89 kidneys, 533 papillae). A significant association was discovered between pitting and RP that held both within and across institutions. A general linear model was then created to further assess this association and it was found that RP score was a highly significant independent correlate of pitting score (F = 7.1; p < 0.001). Mean pitting scores increased smoothly and progressively with increasing RP scores. Sums of the scored domains were then calculated as a reflection of gross papillary abnormality. When analyzed in this way, a history of stone recurrence and shockwave lithotripsy were strongly predictive of higher sums. Conclusions: Renal papillary pathology can be reliably assessed between different providers using a newly described endoscopic grading scale. Application of this scale to stone-forming patients suggests that the degree of RP appreciated in the papilla is strongly associated with the presence of pitting. It also suggests that patients with a history of recurrent stones and lithotripsy have greater burdens of gross papillary disease.

Association Between Randall's Plaque Stone Anchors and Renal Papillary Pits

“…4 Further, application of the system described by Borofsky and coworkers 3 found a strong correlation between pitting and RP. 5 We are now well poised to study the clinical relevance of this finding. For example, might papillary pits be useful as a surrogate marker of stone activity?…”

“…4 Recent investigation of papillary classification among patients undergoing ureteroscopy demonstrated a strong association between RP and papillary pitting and hypothesized that pitting occurred as a result of stone overgrowth on RP with subsequent tearing off of a piece of superficial epithelium with the stone when dislodgement occurred. 5 However, concrete mechanistic evidence for this process is lacking.…”

Classification of the renal papillary abnormalities by flexible ureteroscopy: evaluation of the 2016 version and update

“…In 2016, the first classification (Sx nPx Rx) describing the severity and the type of papillary abnormalities was published, distinguishing the crystallization on RP and the intraductal crystallization (with a ratio of 77 and 13.5%) [4]. In 2017, Cohen [14] demonstrated the correlation between the presence of tip papillary erosions (pits) and RP, confirming the potential etiologic interest of the knowledge of the papillary abnormalities.…”

Endoscopic observations as a tool to define underlying pathology in kidney stone formers

“…All lesions except RP are thought to represent different degrees of nephron loss [14]. In the present study, the original PPLA grading score was modified using numerical values for RP scoring in line with the other domains as suggested by Cohen et al [17]. Each papilla was scored in all domains according to Table 2 and a final PPLA score for each papilla was calculated.…”

“…Technologic advancements in digital endoscopy offer the possibility of detailed inspection of intrarenal anatomy and pathology [14]. Recently, attention has been drawn to the relation between distinct renal papillary abnormalities visualized during endoscopy and unique pathogenetic pathways of stone formation [15–17]. The aim of the present study was to evaluate renal papillary appearance in a consecutive cohort of kidney stone formers undergoing retrograde intrarenal stone surgery (RIRS) using digital flexible ureteroscopes and to correlate the papillary findings with stone type and patient metabolic data to explore the role of endoscopic papillary findings in defining underlying stone-forming mechanisms and clinical outcomes.…”