title: Hounsfield density of renal papillae in stone formers: analysis based on stone composition.
abstract: OBJECTIVE
  We examined renal papillary Hounsfield density in stone formers with all common stone subtypes to further understand the pathophysiology of stone formation.
  
  
  METHODS
  Using computerized tomography we measured the Hounsfield density of a 0.2 cm(2) renal papillary area in patients with a single renal calyceal stone. Results were compared with those in patients without a nephrolithiasis history who served as controls. Stone composition was determined by stone passage or extraction during endoscopic procedures using infrared spectroscopy and polarized microscopy. We measured the Hounsfield density of the stone bearing calyx and of a single calyx from the upper, middle and lower poles of each kidney.
  
  
  RESULTS
  Mean ± SD renal papillary Hounsfield density in controls was 36.2 ± 4.0 HU. In patients with stones Hounsfield density was significantly greater than in controls in stone bearing calyces, nonstone bearing calyces in the affected kidney and calyces in the contralateral nonstone bearing kidney for all stone composition subtypes (range 48.4 to 61.3 HU, each p <0.001).
  
  
  CONCLUSIONS
  Patients with kidney stones regardless of composition showed the unique radiographic characteristic of increased renal papillary Hounsfield density. This was true for all calyces and for each kidney in all stone formers with a single renal calyceal stone. This radiographic evidence supports the role of renal papillary deposits or plaques in the pathophysiology of stone formation.
authors.affiliation: Departments of Radiology and Urology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Sameer
authors.initials: S
authors.lastname: Deshmukh
authors.affiliation: Departments of Radiology and Urology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Avinash
authors.initials: A
authors.lastname: Kambadakone
authors.affiliation: Departments of Radiology and Urology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Dushyant V
authors.initials: DV
authors.lastname: Sahani
authors.affiliation: Departments of Radiology and Urology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts. Electronic address: beisner@partners.org.
authors.forename: Brian H
authors.initials: BH
authors.lastname: Eisner
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000737:chemistry* / Q000000981:diagnostic imaging / Q000473:pathology*; D007679:Kidney Medulla / Q000000981:diagnostic imaging / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
keywords: kidney; kidney calculi; kidney medulla; physiopathology; tomography; x-ray computed