Login to Access Video or Poster Abstract: MP19-14
Sources of Funding: NIH DK056788

Introduction

Renal papillary characteristics among stone formers are suspected to have associations with stone forming pathophysiologies. Papillary pitting (surface erosion) is one of the most common abnormalities encountered and is a component of both recently described papillary classification systems. To date, the mechanism by which pitting occurs is unclear. One hypothesis is that pits are sites where stones overgrowing Randall's plaque (RP) became dislodged. We sought to examine this hypothesis using stone micro CT and high definition renal endoscopy.

Methods

Patients undergoing endoscopic stone removal had their procedures recorded and stones analyzed using micro CT. Patients with stones showing evidence of RP attachment were identified in a manner blinded to patient data. Corresponding surgical videos were reviewed independently by 2 urologists to characterize the RP/renal stone interface and look for papillary pitting.

Results

RP attachments were identified on micro CT in 28 patients (Figure 1). 7.3 RP stones were removed per patient, the majority of whom were recurrent stone formers (93%) with history of prior stone treatment (75%) (Table 1). A majority of patients were categorized as idiopathic calcium oxalate stone formers (78.5%) and metabolic abnormalities on 24 hour urine chemistry were common (86.4%). Pits were identified prior to any stone manipulation on at least one papilla in all cases including 7 who had had no prior procedures (Figure 2).

Conclusions

Stones growing over RP likely pull a piece of tissue away from the papilla when dislodged, leaving visible papillary pits. Identification of pits and incorporation into endoscopic characterization systems for stone formers may help improve patient classification.

Funding

NIH DK056788