Intratubular calcification in a post-renal transplanted patient with secondary hyperparathyroidism

Successful treatment of early allograft dysfunction with cinacalcet in a patient with nephrocalcinosis caused by severe hyperparathyroidism: a case report

Background

Hyperparathyroidism is common in patients undergoing kidney transplantation. Occasionally, this condition can cause early allograft dysfunction by inducing calcium phosphate deposition in the allograft, which results in nephrocalcinosis. Although nephrocalcinosis occurs occasionally in kidney allografts, it has only rarely been reported in the literature.

Case presentation

Here, we present the case of a 58-year-old Thai woman with severe hyperparathyroidism who received a living-related kidney transplant from her 35-year-old son. Our patient developed allograft dysfunction on day 2 post-transplantation despite good functioning graft on day 1. Allograft biopsy showed extensive calcium phosphate deposition in distal tubules. She was treated with cinacalcet (a calcimimetic agent) and aluminum hydroxide. Allograft function was restored to normal within 1 week after transplantation with greatly reduced intact parathyroid hormone level.

Conclusion

Hyperparathyroidism in early functioning allograft causes elevated calcium and phosphate concentration in distal tubules resulting in nephrocalcinosis. The massive calcium phosphate precipitation obstructs tubular lumens, which leads to acute tubular dysfunction. Treatment of nephrocalcinosis with cinacalcet is safe and may improve this condition by increasing serum phosphate and reducing serum calcium and intact parathyroid hormone.

Early allograft calcifications after kidney transplantation

Early allograft calcifications after kidney transplantation (KT) have already been reported, but the clinical implications of this finding are not clear thus far. Patient-related factors such as age, gender, underlying renal disease, and dialytic modality, seem to be irrelevant. It has been postulated that factors promoting the development of metastatic calcifications, including elevated calcium phosphate product and severe secondary hyperparathyroidism, could play a causal role. Here we report a case of a KT patient who developed early kidney calcifications which were associated with severe allograft dysfunction.

Kidney allograft failure due to acute phosphate nephropathy associated with severe secondary hyperparathyroidism

Intratubular calcification is a common finding in renal allografts. However, possible harmful effect of this calcification is not well recognized, and allograft failure purely due to this condition has not been reported. We report a kidney transplant recipient who suffered from severe secondary hyperparathyroidism and unexplained early allograft failure. A diagnosis of acute phosphate nephropathy was made subsequently based on serial allograft biopsy findings. This case calls for a high index of suspicion to look for this rare cause of allograft dysfunction among high-risk patients. It also highlights the importance of good calcium–phosphate control before renal transplantation.

Elevated calcium phosphate product after renal transplantation is a risk factor for graft failure

BACKGROUND

Abnormal mineral metabolism is not uncommon after renal transplant (TXP). In dialysis patients, elevated serum phosphorous (P), calcium (Ca), CaP product, and parathyroid hormone (PTH) are associated with increased morbidity and mortality. The effect of these abnormalities on recipient and graft survival after renal transplantation is unknown.

METHODS

We retrospectively analyzed 422 kidney-only transplants performed between June 1996 and June 2003. Cases with graft or recipient survival less than three months, pre-TXP parathyroidectomy (PTX), cinacalcet therapy and incomplete records were excluded, leaving 303 cases for analysis using Cox models that included post-TXP PTX, levels of albumin-adjusted Ca(Ca(adj)), P, Ca(adj)P product and PTH.

RESULTS

There was an 11-25% prevalence of abnormal serum Ca(adj), P or Ca(adj)P product within the first year post-TXP. At least 24% of recipients not undergoing PTX with an equation estimated GFR of 40-60 mL/min had PTH levels >130 pg/mL at one yr post-TXP. This is above levels recommended by the U.S National Kidney Foundation kidney disease quality initiative for patients with stages I-IV chronic kidney disease. Adjusted Ca > 10.5 mg/dL at three months post-TXP was an independent risk for recipient death (OR 3.0; 95% CI: 1.2-7.4). A Ca(adj)P product >35 mg(2)/dL(2) at six months (OR 4.0; 95% CI: 1.2-13.1), and Ca >10.5 mg/dL at 12 months post-TXP (OR 4.0; 95% CI: 1.2-14) were independent risks for death-censored graft loss. Twenty-two recipients underwent PTX for severe hyperparathyroidism.

CONCLUSION

Abnormalities of mineral metabolism are common early after renal TXP. An elevated serum Ca(adj) at three months post-TXP increases the risk for recipient death, while an elevated Ca(adj)P and Ca(adj) later in the first post-TXP year increases the risk of long-term death-censored graft loss.

Early calcification of renal allografts detected by protocol biopsies: causes and clinical implications

Interstitial calcification has been described in renal allografts, however, the etiology and significance of this finding for the graft are unclear. The aim of this study was to examine calcification in serial protocol biopsies, to test the hypothesis that calcification is related to parameters of calcium homeostasis in these patients and to analyze a possible relation between calcification and graft function at 1 year. We studied 213 patients with 586 protocol biopsies obtained 6 weeks, 3 and 6 months after transplantation. Calcifications increased over time, from 6.1% at 6 weeks to 17.8% at 6 months. Out of the 213 patients, 56 had calcification in one or more biopsies. Patients age and gender, underlying renal disease, dialysis mode and duration, previous transplantations, donor type, age and gender, HLA matches and ischemia time had no influence on calcification. Calcification was not related to rejection episodes, acute tubular lesions, calcineurin inhibitor toxicity or tubulointerstitial fibrosis and tubular atrophy. Patients with calcification had significantly higher serum parathormone and calcium levels. In patients with calcification, high PTH levels correlated with an inferior outcome of graft function at 1 year after transplantation (p<0.05). Therefore, treatment of hyperparathyroidism should be considered earlier and more often in these patients.