Diet-related urine collections: assistance in categorization of hyperoxaluria

Abstract

Hyperoxaluria, one of the major risk factors for calcium oxalate urolithiasis and nephrocalcinosis, causes significant morbidity and mortality and should therefore be detected and treated as soon as possible. An early, consequent and adequate evaluation, but also a distinction between primary (PH) and secondary hyperoxaluria (SH) is therefore essential. We evaluated the usefulness of three consecutive 24-h urine collections under different diets [usual diet, (A), low oxalate diet, (B), high oxalate diet, (C)] to prove SH, or to find evidence of PH by changes in urinary oxalate excretion (Uox). We retrospectively analyzed results from 96 pediatric patients (47 females and 49 males, age 3–18 years) who presented with a history of nephrolithiasis, nephrocalcinosis and/or persistent hematuria in whom hyperoxaluria was found in an initial urine sample. The typical pattern of SH was found in 34 patients (mean Uox (A) 0.85 ± 0.29, (B) 0.54 ± 0.15 and (C) 0.95 ± 0.28 mmol/1.73m2/d). PH was suspected in 13 patients [(A) 1.21 ± 0.75; (B) 1.47 ± 0.51 and (C) 1.60 ± 0.82 mmol/1.73m2/d], but genetically proven only in 1/5 patients examined. No hyperoxaluria was found in 16 patients. Data were inconclusive in 33 patients. Urine collection under different diets is helpful to diagnose secondary hyperoxaluria and may provide evidence, that urinary oxalate excretion is normal. We have now established this procedure as our first diagnostic step before further, more extensive and more expensive evaluations are performed.

Impact of low‐oxalate diet on hyperoxaluria among patients suffering from nephrolithiasis

“…Similar results were found by Dill et al. ( 2022 ) who mentioned that a low‐oxalate diet is helpful in the reduction of creatinine level. Low‐oxalate diet maintains the creatinine level at a normal range.…”

“…The result of this study showed a significant (p = .000) decrease in creatinine levels with the help of a low-oxalate diet as shows in Table 3. Similar results were found by Dill et al (2022) who mentioned that a low-oxalate diet is helpful in the reduction of creatinine level. Low-oxalate diet maintains the creatinine level at a normal range.…”

“…An excess oxalate and glycolate are generated as an outcome of the deficit, which causes glyoxylate to accumulate (Witting et al., 2021 ). It has been established that the alanine glyoxylate aminotransferase gene mutation on chromosome 2 is associated with an absence of a B6‐dependent enzyme (AGT) (Dill et al., 2022 ).…”

Navigating the Evolving Landscape of Primary Hyperoxaluria: Traditional Management Defied by the Rise of Novel Molecular Drugs

“…Radiolabeled isotope studies confirm that the kidneys mainly excrete oxalate (>90%), which is a highly insoluble end-product of human metabolism [4,5]. Glomerular filtration and tubular net secretion maintain a physiological oxalate excretion range of 10-40 mg/day (0.1-0.45 mmol/day); however, PH patients exhibit oxalate excretion exceeding 40-45 mg/day (0.45-0.5 mmol/day), accompanied by various systemic manifestations [6,7]. The deposition of calcium oxalate (CaOx) in the renal tubules and interstitium in PH can cause chronic tubulointerstitial inflammation and kidney stone obstruction, resulting in renal failure in over 70% of cases [8].…”