Crystals in renal allograft biopsies; a 5-year study with review of literature

Abstract

Introduction: The kidney is exposed to a variety of crystalline substances which can cause tissue damage. There are limited studies on the frequency of crystal deposits in renal allograft biopsies especially from our part of the world. Objectives: The objective of this study was to find out the prevalence of crystal deposits among the allograft biopsies received at our centre over five years, and to identify its clinicopathological implications. Patients and Methods: We have retrospectively searched the records of renal biopsies reported during the period from 2014 to 2018, to identify allograft biopsies with crystal deposits. The histopathological findings including the density of deposits were noted and correlated with demographic and clinical profile in the light of available literature. Results: Of 1225 transplant biopsies received during the study period, 1.5% had crystal deposits reported on morphology. These biopsies were from 13 patients evaluated for graft dysfunction; 10 had oxalate crystals while three had the rare 2,8-dihydroxyadenine (DHA) crystals. Crystal density varied from 1 to 26/mm2 and all showed acute tubular injury. Around 39% of the biopsies with crystals, included in this study, were taken within a month of transplant and those cases with subsequent biopsies showed progressive interstitial fibrosis/tubular atrophy (IF/TA). All three cases of DHA nephropathy were first diagnosed only on allograft biopsies. Conclusion: In the process of graft dysfunction, interpretation of allograft biopsy should include a careful search for crystals including polarised microscopy as this might not only explain deterioration of renal function, but also clinch the diagnosis of native kidney disease. Though our study has limitations, it addresses a less discussed issue and further studies are required to reinforce the significance of crystal induced allograft injury.