title: Endoscopic and histologic findings in a cohort of uric acid and calcium oxalate stone formers.
abstract: OBJECTIVE
  To characterize the endoscopic and histologic renal papillary lesions in a cohort of uric acid (UA) stone formers (SF).
  
  
  METHODS
  Data were prospectively obtained during percutaneous nephrolithotomy between 2009 and 2013. Renal papillae were endoscopically analyzed to quantitate surface area occupied by plaque or plug, and biopsies were obtained. UA SF were compared with non-SF controls and patients with >50% calcium oxalate (CaOx) in the absence of UA.
  
  
  RESULTS
  There were 23 UA SF; of which 19 stones (83%) were admixed with CaOx and 4 (17%) were pure. Compared with CaOx SF and controls, UA SF had a higher prevalence of diabetes and obesity, greater serum creatinine and UA levels, lower estimated glomerular filtration rate and urine pH, and elevated UA supersaturation. Characteristics of UA SF were compared with 95 CaOx SF and 19 controls. Overall, 23 (100%) UA SF had endoscopic plaque and 13 (57%) plugs. Endoscopically, UA SF displayed a greater incidence of plugging (57% vs 45% vs 11%; P = .006) relative to CaOx SF and controls. Likewise, UA SF had a greater percentage surface area of plugging (0.1 vs 0.0; P = .002) and plaque (2.0 vs 0.9; P = .006) than controls but similar amounts to CaOx SF. Histologic plugs were similar in UA and CaOx SF, although CaOx SF demonstrated greater interstitial inflammation on endoscopic biopsy.
  
  
  CONCLUSIONS
  UA and CaOx SF have similar amounts of plaque, whereas UA SF have more endoscopic but not histologic collecting duct plugs. These data suggest an overlap between the pathogenesis of UA and CaOx stones. The anchoring site for UA stones remains uncertain.
authors: Department of Urology, Mayo Clinic, Rochester, MN.
authors: Boyd R
authors: BR
authors: Viers
authors: Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN; Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN.
authors: John C
authors: JC
authors: Lieske
authors: Department of Radiology, Mayo Clinic, Rochester, MN.
authors: Terri J
authors: TJ
authors: Vrtiska
authors: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN.
authors: Loren P
authors: LP
authors: Herrera Hernandez
authors: Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN.
authors: Lisa E
authors: LE
authors: Vaughan
authors: Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN.
authors: Ramilia A
authors: RA
authors: Mehta
authors: Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN.
authors: Eric J
authors: EJ
authors: Bergstralh
authors: Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN; Division of Epidemiology, Mayo Clinic, Rochester, MN.
authors: Andrew D
authors: AD
authors: Rule
authors: Department of Physiology and Biomedical Engineering, Biomedical Imaging Resource Core, Mayo Clinic, Rochester, MN.
authors: David R
authors: DR
authors: Holmes
authors: Department of Urology, Mayo Clinic, Rochester, MN. Electronic address: Krambeck.amy@mayo.edu.
authors: Amy E
authors: AE
authors: Krambeck
mesh_terms: D000368:Aged; D001706:Biopsy; D002129:Calcium Oxalate; D016022:Case-Control Studies; D003404:Creatinine / Q000097:blood; D003920:Diabetes Mellitus / Q000453:epidemiology; D004724:Endoscopy; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007669:Kidney Calculi / Q000737:chemistry* / Q000473:pathology*; D007679:Kidney Medulla / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009393:Nephritis / Q000473:pathology*; D009403:Nephrostomy, Percutaneous; D009765:Obesity / Q000453:epidemiology; D011446:Prospective Studies; D014527:Uric Acid
chemical_list: D002129:Calcium Oxalate; D014527:Uric Acid; D003404:Creatinine