Some Observations on the Demonstration of Calcium Oxalate in Tissue Sections

Crystal deposits in human kidney and thyroid, identified as calcium oxalate by microincineration and Solubility tents, were used to assess the staining of oxahtes by selected methods for calcium. No method that stained the crystals was considered specific for calcium oxalate, but, after removal of possible phosphate and carbonate with 2 M acetic acid, the silver nitrate-rubeanic acid sequence was found to give the best visualisation of the crystals, and could be considered reasonably selective. Deposits in kidneys included a pronounced colloidal matrix composed chiefly of acid mucopolysaccharides. This matrix often showed a lamellar pattern and was well-demonstrated by alcian blue at pH 25 and by dialysed iron after removal of the crystals with 1 N hydrochloric acid. Such a matrix Could only be detected in trace amount in the thyroid deposits.