Calcium oxalate crystal deposition in the kidney: identification, causes and consequences

J A Sayer,R Geraghty,K Wood

doi:10.1007/s00240-020-01202-w

Abstract

Calcium oxalate (CaOx) crystal deposition within the tubules is often a perplexing finding on renal biopsy of both native and transplanted kidneys. Understanding the underlying causes may help diagnosis and future management. The most frequent cause of CaOx crystal deposition within the kidney is hyperoxaluria. When this is seen in native kidney biopsy, primary hyperoxaluria must be considered and investigated further with biochemical and genetic tests. Secondary hyperoxaluria, for example due to enteric hyperoxaluria following bariatric surgery, ingested ethylene glycol or vitamin C overdose may also cause CaOx deposition in native kidneys. CaOx deposition is a frequent finding in renal transplant biopsy, often as a consequence of acute tubular necrosis and is associated with poorer long-term graft outcomes. CaOx crystal deposition in the renal transplant may also be secondary to any of the causes associated with this phenotype in the native kidney. The pathophysiology underlying CaOx deposition is complex but this histological phenotype may indicate serious underlying pathology and should always warrant further investigation.

Highlights

Calcium oxalate (CaOx) crystal deposition within the nephron [1–3], tubular cells [4] or interstitium [5] are sometimes found by the histopathologist examining a renal biopsy
CaOx, along with calcium phosphate (CaP) deposition may lead to nephrocalcinosis [6, 7], in practice CaOx crystal deposition is often referred to as renal oxalosis or oxalate nephropathy
Much of the clinical literature describing conditions associated with CaOx crystal deposition are case reports

Summary

Introduction

Calcium oxalate (CaOx) crystal deposition within the nephron [1–3], tubular cells [4] or interstitium [5] are sometimes found by the histopathologist examining a renal biopsy. CaOx, along with calcium phosphate (CaP) deposition may lead to nephrocalcinosis [6, 7], in practice CaOx crystal deposition is often referred to as renal oxalosis or oxalate nephropathy. Bagnasco et al examined biopsies of both native and transplanted kidneys over the course of 6 years [6]. 1% of native kidney biopsies and 4%. Of transplanted kidney biopsies demonstrated CaOx crystal deposition. The presence of CaOx crystal deposition within a renal biopsy may indicate serious underlying pathology and indicate an underlying diagnosis that may not have previously been considered [7, 8]. The diagnosis of PH has potentially life-changing effects with a broad range of treatment options, up to and including dual kidney and liver transplant [9, 10]

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