title: Tubular and interstitial nephrocalcinosis.
abstract: OBJECTIVE
  We determined whether nephrocalcinosis is common and whether its detection is influenced by renal tissue processing.
  
  
  METHODS
  Renal cortical and papillary tissue was obtained from the unaffected parts of 15 kidneys removed due to an oncological indication. The effect of tissue processing on the loss of crystals was studied in a kidney with nephrocalcinosis due to chronic pyelonephritis. Immediately frozen and formaldehyde fixed sections were analyzed by polarized light and Raman spectroscopy, and stained for calcium (Yasue) and hyaluronan.
  
  
  RESULTS
  Although 13 of 15 snap-frozen sections from tumor kidneys contained birefringent particles (mean +/- SD 3.2 +/- 2.9 particles per cm(2)) in the renal tubules, this was not considered nephrocalcinosis because the crystals were not attached to the epithelial lining. Interstitial nephrocalcinosis was found on Yasue stain in 3 of 15 kidneys with tumor (20%). Calcium deposits were found in the papillary interstitium only, always together with hyaluronan. Formaldehyde fixed sections from the pyelonephritis kidney contained fewer renal tubular cell associated birefringent particles than immediately frozen sections (9.4 +/- 1.9 vs 41.6 +/- 1.2 per cm(2)). Particles were composed of calcium oxalate monohydrate (Yasue and Raman).
  
  
  CONCLUSIONS
  There are 2 distinct forms of nephrocalcinosis, including tubular nephrocalcinosis, which seems to be reserved for specific conditions such as chronic pyelonephritis, and interstitial nephrocalcinosis. The incidence of tubular calcium oxalate nephrocalcinosis could be underestimated due to the loss of crystals during tissue processing for routine histology. The crystal binding molecule hyaluronan may have a role in the 2 forms of nephrocalcinosis.
authors.affiliation: Department of Urology, Erasmus Medical Center Rotterdam, Rotterdam, The Netherlands.
authors.forename: Maxime T M
authors.initials: MT
authors.lastname: Kummeling
authors.forename: Bas W D
authors.initials: BW
authors.lastname: de Jong
authors.forename: Charlie
authors.initials: C
authors.lastname: Laffeber
authors.forename: Dirk-Jan
authors.initials: DJ
authors.lastname: Kok
authors.forename: Paul C M S
authors.initials: PC
authors.lastname: Verhagen
authors.forename: Geert J L H
authors.initials: GJ
authors.lastname: van Leenders
authors.forename: Ron H N
authors.initials: RH
authors.lastname: van Schaik
authors.forename: Christiaan S
authors.initials: CS
authors.lastname: van Woerden
authors.forename: Anja
authors.initials: A
authors.lastname: Verhulst
authors.forename: Carl F
authors.initials: CF
authors.lastname: Verkoelen
mesh_terms: D005260:Female; D005629:Frozen Sections; D006652:Histological Techniques; D006801:Humans; D007672:Kidney Cortex / Q000473:pathology*; D007679:Kidney Medulla / Q000473:pathology*; D008875:Middle Aged; D009397:Nephrocalcinosis / Q000473:pathology*; D013059:Spectrum Analysis, Raman; D014961:X-Ray Diffraction