Vitamin C-induced hyperoxaluria causing reversible tubulointerstitial nephritis and chronic renal failure: a case report

UNLABELLED Vitamin C is a precursor of oxalate and promoter of its absorption, potentially causing hyperoxaluria. Malabsorption causes Calcium (Ca) chelation with fatty acids, producing enteric hyperoxaluria. CASE A 73-year-old man with both risk factors was hospitalized with serum creatinine of 8.4 mg/dL (versus 1.2 mg/dL four months earlier) (normal 0.6-1.3 mg/dL). Given his oxalate-rich diet, chronic diarrhea, and daily 680 mg vitamin C and furosemide, we postulated Ca oxalate-induced nephropathy, a diagnosis confirmed by documenting hyperoxaluria, and finding of diffuse intraluminal crystals and extensive interstitial fibrosis on biopsy. He was hemodialysed 6 times to remove excess oxalate. Two weeks off vitamin C, his creatinine spontaneously fell to 3.1 mg/dL. Three months later, on low oxalate diet and 100 mg vitamin B6, urine oxalate to creatinine ratio decreased from 0.084 to 0.02 (normal < 0.035), while creatinine fell and stayed at 1.8 mg/dL. CONCLUSION 1) High-dose vitamin C can induce hyperoxaluric nephropathy and progressive renal failure, especially if aggravated by diarrhea, oxalate-rich diet, metabolic acidosis, and dehydration. 2) The diagnosis should be suspected in unexplained renal insufficiency when associated with these risk factors. 3) Since prompt treatment could avert end-stage renal disease, we recommend monitoring urinary oxalate in patients on high-dose vitamin C and renal biopsy if necessary.