Introduction: Irritable bowel syndrome (IBS) management often includes dietary intervention. Some individuals consume high oxalate foods to decrease IBS symptoms. High oxalate foods include tea, beans, nuts, spinach, kale, rhubarb, beets and soy. Factors influencing absorption include dose ingested, mineral content of the meal, and fat malabsorption. Oxalate is excreted in urine and excessive filtration can cause oxalate nephropathy. We describe a rare case of a high oxalate diet intended for irritable bowel syndrome (IBS) treatment causing nephropathy.
Methods: A 59 year old Caucasian woman with chronic kidney disease (stage 3), IBS, osteoporosis, hypertension and hyperthyroidism presented with worsening renal function during a follow up evaluation. She reported a high oxalate diet for her IBS symptoms, consisting of 6 tablespoons of chia seeds and multiple servings of almonds daily. She denied history of urinary stones. Medications included amlodipine and methimazole. She denied NSAID use, never smoked and drank alcohol occasionally. Her family history was significant for diabetic nephropathy in her father.
Labs revealed an increase in creatinine from 1.3 to 1.8 over six months. Urinalysis was negative for proteinuria and hematuria. A renal ultrasound was normal. A subsequent renal biopsy showed glomerulosclerosis, fibrosis, tubular atrophy, and calcium oxalate deposition. Immunofluorescence was negative. Litholink showed increased oxalate and low citrate in urine. Her acute kidney injury was attributed to diet. She switched to a low oxalate diet with high fluid intake and started calcium carbonate with meals and vitamin D. A two month follow up evaluation revealed that her creatinine improved to 1.57 and urine studies showed decreased oxalate. Discussion: This case reveals the unintended consequence of a high oxalate diet for IBS symptoms. There is a close relationship between diet, intestinal health, and kidney health, signifying the importance of a thorough dietary history, nutrition counseling, and dietary management of disease. Vulnerable patients include those with chronic kidney disease, calcium and iron deficiencies, fat malabsorption, and those following a plant based or a fad diet. Risk can be mitigated with cooking techniques, hydration, balancing high oxalate diets with foods rich in free calcium, magnesium and iron and by limiting high oxalate foods. The microbiome appears to play an important role in degrading oxalate and in the future may further help stratify risk.