SAT-460 HISTOLOGICAL DIAGNOSIS OF HYPEROXALURIA FROM RENAL BIOPSY

Abstract

Crystal-induced kidney disease refers to kidney injury caused by intratubular crystal deposition. The most common forms of crystalline nephropathy encountered in renal pathology are nephrocalcinosis and oxalate nephropathy. The purpose of our study is to determine the epidemiological and clinical characteristics of hyperoxaluria diagnosed from renal biopsy. We retrospectively reviewed all kidney biopsy specimens evaluated at renal pathology laboratory, from 1976 to 2018. The biopsy specimens were received from multiple medical department and medical centers. We studied 8900 biopsy specimens and we were focused on patients whose diagnosis of hyperoxaluria was made from renal biopsy. We identified 25 cases (15 children and 10 adults) with a sex ratio H / F of 0.9. Mean age at diagnosis was 17.2 years old [4 months-73 years old]. Most patients were offspring of consanguineous mating (14 of 25) with intermarriage of first-degree cousins being the most common pattern. A family history of chronic kidney disease was found in 13 patients: indeterminated nephropathy (n = 6) and renal stone (n = 5) and primary hyperoxaluria (n=2). Among our patients, five had a history of urolithiasis. One patient had a history of chronic diarrhea related to Crohn's disease and one patient had a history of cephalic pancreatectomy and ileal resection. Initial symp­toms and signs were dominated by renal failure (n = 25) with mean creatinine of 789.5 μmol / l [306-1832μmol / l], associated with proteinuria in 10 patients and hematuria in 11 patients. Arterial hypertension was present in 4 patients. Oligo anuria was reported in 4 patients without dilation of the urinary excretory pathways. In our patients, the diagnosis of crystalin nephropathy was revealed by renal biopsy. In one case, the diagnosis was made after renal transplant. In 4 cases the diagnosis was made by postmortem kidney biopsy. In all cases, the kidney biopsy specimen showed extensive intratubular crystal deposition and tubulointerstitial mononuclear cell infiltration with features of tubular injury and interstitial fibrosis. Examination of histologic slides showed colorless refractile crystals of polygonal appearance. Multicolored birefringence under polarized light identified these crystals as calcium oxalate. After different investigations (genetic and biological analysis), the diagnosis of hyperoxaluria was confirmed. Hyperoxaluria was primary in 23 patients and secondary in 2 patients. Hyperoxaluria is a rare condition, often serious, involving renal prognosis and sometimes life-threatening, especially in early-onset forms. Early diagnosis and treatment should be done as soon as possible to slow the progression to end-stage renal failure. In patients with renal insufficiency, the diagnosis of hyperoxaluria is difficult. Renal biopsy can help when clinical and radiological data are not sufficient.