From Health to Harm: Acute Oxalate Nephropathy in a Weightlifter

Introduction: Oxalate nephropathy is a rare condition characterized by deposition of calcium oxalate within the kidney tubules, typically associated with acute tubular injury. This phenomenon arises from an excess of urinary calcium oxalate, leading to the precipitation of insoluble calcium oxalate crystals within the kidney tubules. Case Description: A healthy 33-year-old male presented with four days of nausea and vomiting. Laboratory work up showed his serum creatinine (SCr) was 5.4 mg/dL and BUN was 53 mg/dL, compared to a SCr of 1 mg/dL four years prior. Urinalysis revealed 27 RBC/hpf and no protein; with imaging showing no hydronephrosis. A kidney biopsy demonstrated diffuse acute tubular injury with associated calcium oxalate deposition in tubular lumens (see figure 1), consistent with acute oxalate nephropathy. SCr improved modestly to 4.8 mg/dL after 48 hours of aggressive hydration. The patient reported no prior abdominal surgeries, diarrhea, or vitamin C supplements. Upon further questioning, the patient disclosed a rigorous weight training regimen, along with the use of several supplements including a pre-workout and creatine. He was eating a high protein diet and juicing with an abundance of spinach. He was instructed to discontinue juicing and all supplements. Subsequent investigation post-discharge revealed normal vitamin B6 levels, SCr 3.8 mg/dL, 24-hour urine oxalate 76 mg/day (normal <45 mg/day), urine sodium 528 mmol/volume, urine calcium 216 mg/volume, uric acid 954 mg/volume, creatinine clearance 68 mL/min, and total urine volume 6L/day. Discussion: Secondary hyperoxaluria from excessive ingestion of high oxalate foods is uncommon. Juicing of green leafy vegetables provides large oxalate loads (spinach: ~650mg oxalate/cup). Exercise supplementation, widely used by amateur and professional athletes, is believed to enhance athletic performance yet is largely unregulated. With the escalating popularity of juicing and exercise supplementation, consulting healthcare professionals can help individuals navigate risks and benefits.Figure 1: H&E stain with oxalate crystals under polarized light