Early Presence of Calcium Oxalate Deposition in Kidney Graft Biopsies is Associated with Poor Long-Term Graft Survival

Abstract

Accumulated oxalate will be excreted after renal transplantation, creating an increased risk of tubular precipitation, especially in the presence of allograft dysfunction. We evaluated calcium oxalate (CaOx) deposition in renal allograft biopsies with early dysfunction, its association with acute tubular necrosis (ATN) and graft survival. We studied 97 renal transplant patients, submitted to a graft biopsy within 3 months post-transplant, and reanalyzed them after 10 years. We analyzed renal tissue under polarized light and quantified CaOx deposits. CaOx deposits were detected in 52.6% of the patients; 26.8% were of mild and 25.8% of moderate intensity. The deposits were more frequent in biopsies performed within 3 weeks post-transplant (82.4 vs. 63.0%, p < 0.05) and in allografts with more severe renal dysfunction (creatinine 5.6 mg/dL vs. 3.4 mg/dL, p < 0.001). ATN incidence was also higher in patients with CaOx deposits (47% vs. 24%, p < 0.001). Twelve-year graft survival was strikingly worse in patients with CaOx deposits compared to those free of deposits (49.7 vs. 74.1%, p = 0.013). Our study shows a high incidence of CaOx deposits in kidney allografts with early dysfunction, implying an additional risk for acute tubular injury, with a negative impact on graft survival.

Enteric Oxalate Nephropathy in the Renal Allograft: An Underrecognized Complication of Bariatric Surgery

“…Oxalate crystals in renal biopsy specimens have characteristic morphology, as described in the cases above, yet may be difficult to recognize (Figure 1 (29). In each of these studies, oxalate crystals were associated with acute tubular injury/necrosis, and may rarely be associated with delayed graft function ( (Table 2).…”

“…Further, although dialysis does remove oxalate to a varying degree dependent upon method and duration, dialysis does not normalize oxalate levels in end stage renal disease (27,28). In the immediate posttransplant period, the allograft clears excess plasma oxalate, which results in transient hyperoxaluria usually lasting from 3 days to 3 weeks (25,26,29,30). Several studies have characterized the typical plasma and urine oxalate profile in transplant recipients.…”

Surgical management of secondary hyperparathyroidism in chronic kidney disease—a consensus report of the European Society of Endocrine Surgeons

“…3. There are current reports of different groups suggesting that a Bless than subtotal^PTX could lead to similar rate of cure in a significant proportion of patients (around 30 %) when this rate of cure is indicated by the normalization of the calcium level [51,131,141].…”

“…Severe persistent renal HPT is associated with hypercalciuria. Nephrocalcinosis is an independent risk for chronic allograft nephropathy knowing that nephrocalcinosis decreases 12-year allograft survival from 75 to 48 % [131] (EL 3).…”

Oxalate Nephropathy Associated with Chronic Pancreatitis

“…Scarce or isolated tubular deposits of oxalate crystals is not a rare finding in the normal or failing kidney at any stage, and even in the transplanted kidney. Isolated oxalate crystals do not imply renal damage, although oxalate deposits in kidney grafts have a negative effect on long-term renal function (18,19). In contrast, abundant tubular or interstitial deposits of calcium oxalate are highly suggestive of a hyperoxaluric condition in native or transplanted kidney.…”