Calcium oxalate microdeposition in failing kidney grafts

Abstract

Forty allograft nephrectomies (28 males and 12 females, mean age of 33.2 years), performed between 1986 and 1999, were selected. Twenty patients had been grafted from cadaveric donors; of the remaining cases, 15 had received a kidney from a living related donor. Except for six patients who received steroid-azathioprine immunosuppression, all recipients were treated with cyclosporine A and low doses of steroids. None had primary or acquired hyperoxaluria as the cause of original end-stage renal disease, and none had a history of kidney stones or urinary infection. Kidney failure occurred after a time period ranging from 2 days to 11 years posttransplant and was secondary to acute rejection in 17 cases, chronic rejection in 15, ischemic necrosis in five, acute or chronic pielonephritis in two, and allergic microangiopathy in one. No blood chemistry evaluations for oxalemia were performed. Clinical data are summarized in Table 1. Multiple sections cut from formalin-fixed, paraffin-embedded blocks and stained with haematoxylin-eosin (H&E) were examined using partially crossed polarizing screens. The presence of calcium oxalate crystals in different segments of the nephron or in the interstitium was recorded. Birefringent deposits with characteristic green iridescence, presenting as large plate-like or diamondshaped crystals, or any shape, provided that the crystals displaced tissue structures, were studied. Confirmation of the crystal nature was obtained using Yasue’s method, a histochemical stain considered to be specific for calcium oxalate, while usual stains for calcium (alizarin red and von Kossa’s method) were negative. Silver nitrate–rubeanic acid with 5% acetic acid pretreatment (Yasue’s method) stains only calcium oxalate, since calcium phosphate and calcium carbonate are dissolved with the acetic acid. A thyroid with multiple deposits of calcium oxalate and hydroxyapatite crystals was used as a positive control for the histochemical stains.