Staining method for kidney biopsy image
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* Henry Schneiderman MD

*   © 2008 Canadian Medical Association

Ami Schattner and colleagues' description of a case of acute phosphate nephropathy1 is of great interest and offers important information about the safest choice of bowel-cleansing preparations. I have a question about Figure 1: Was it not prepared using von Kossa stain rather than hematoxylin–eosin stain? The von Kossa staining method is not specific for calcium but is commonly used as though it were. The background renal parenchyma in the authors' image looks washed out, although the nuclei are more lilac than expected with the standard counterstain. The calcium phosphate salts in Figure 1 are black and dark grey, whereas in undecalcified tissue sections stained with hematoxylin-eosin, the calcium is usually an intense basophilic blue-purple. When the von Kossa staining method is used, silver replaces the calcium (or another substance) and shows up as black or very dark burnt umber, as in the authors' image.

## Footnotes

*   **Competing interests:** None declared.

## REFERENCE

1.  1. Schattner A, Kopolovic J, Melzer E, et al. A 71-year-old woman with abdominal pain and acute renal failure. CMAJ 2007;177:454-5.
    
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