Chronic Nephropathy from Dietary Hyperoxaluria: Sustained Improvement of Renal Function after Dietary Intervention

Abstract

A 56-year-old man with stable chronic kidney disease (CKD) for two years following a single episode of calcium oxalate urolithiasis developed progressive elevation of his serum creatinine concentration. Urinalysis revealed pyuria and white cell casts, a few red blood cells, minimal proteinuria, and no crystals. Urine culture was sterile. Gallium scintigraphy was consistent with interstitial nephritis. Proton pump inhibitor intake was discontinued, and a short course of oral corticosteroids was initiated. Percutaneous kidney biopsy, performed because of the continued deterioration of renal function to a minimum estimated glomerular filtration rate (eGFR) value of 15 mL/min per 1.73 m2 and persistent pyuria, revealed deposition of oxalate crystals in the tubules and interstitium, pronounced tubular changes, and interstitial nephritis and fibrosis. Urinary oxalate excretion was very high, in the range usually associated with primary hyperoxaluria. However, investigations for primary or enteric hyperoxaluria were negative. He reported a diet based on various nuts high in oxalate content. Estimated oxalate content in the diet was, for years, approximately four times higher than that in the average American diet. The institution of a diet low in oxalates resulted in the rapid normalization of urinary oxalate excretion and urinary sediment and in the slow, continuous improvement of renal function to near normal levels (eGFR 59 mL/min/1.73 m2) before his death from a brain malignancy 3.5 years later. The manifestations of nephropathy secondary to dietary hyperoxaluria, including the urine findings, can be indistinguishable from other types of interstitial nephritis. The diagnosis of dietary hyperoxaluria requires careful dietary history and a kidney biopsy. Identifying dietary hyperoxaluria as the cause of CKD is important because the decrease in dietary oxalate intake without any other measures can lead to sustained improvement in renal function.

Secondary Oxalate Nephropathy: A Systematic Review

“…A total of 14,160 potentially relevant citations were identified and screened; 430 titles and abstracts were screened using the inclusion and exclusion criteria; 147 were excluded on the basis of the title and abstract review; and 283 articles were retrieved for detailed evaluation, of which 67 fulfilled the eligibility criteria, which involved 108 patients ( Figure 1 ). 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , …”

“…All patients received hydration and dietary interventions, including the adoption of a normal calcium, low-oxalate diet. In addition, the use of diuretics for fluid overload, 15 , 46 , 70 alkali therapy to alkalinize the urine, 10 , 19 , 46 , 53 and pyridoxine to convert glyoxalate (the main precursor of oxalate) to glycine 15 , 19 , 44 , 48 , 65 , 70 was variably reported and had inconsistent impact on recovery of kidney function ( Supplemental Table S1 ).…”

72-Year-Old Woman With Fatigue, Confusion, and Severe Acute Renal Failure

“…1 Excessive urinary oxalate excretion can be due to primary endogenous overproduction of oxalate, excess exogenous oxalate intake and/or absorption, or decreased renal clearance. 1,3,10 Serum oxalate levels in adults vary below 1 to 3 mmol/L but can be elevated up to 45 mmol/L in patients undergoing hemodialysis patients. 3 Malabsorptive bariatric surgeries, such as RYGB, can cause secondary oxalate nephropathy due to intestinal oxalate absorption.…”

Lost Seasonality and Overconsumption of Plants: Risking Oxalate Toxicity

“…Because objective tests of urine 141 and tissue biopsy 37 are unreliable, oxalate-related symptoms go unrecognized as such. Despite several recent medical case reports that faulted the consumption of peanuts 8,142,143 , green juices 8 and smoothies 144 , tea 145 , nuts and nut butter 146 , cashews 147 , and a weight loss diet consisting of spinach, kale, berries, and nuts 148 for kidney failure in patients, oxalates remain obscure compounds of no special concern in modern health care.…”

“…There are many therapeutic and preventive benefits of avoiding dietary oxalates, including improvements in kidney function 87,88,146,[151][152][153][154] . In addition, both published and unpublished reports suggest benefits such as reversal of neurotoxicity (brain fog, cognition, behavioral and mood disorders, and sleep improvements 155 ), recovery of connective tissue stability 89, 156 and reduced symptoms of autoimmunity 136 .…”