Large Case Series Identifies Key Clinical, Pathological Characteristics of Patients With Oxalate Nephropathy

In one of the largest native oxalate nephropathy (ON) cohorts from a US tertiary care institution to date, researchers identified key characteristics among patients with ON, including high rates of diabetes, nephrolithiasis, and multifactorial risk factors.

Oxalate nephropathy is a rare and commonly underrecognized cause of chronic kidney disease (CKD) and end-stage kidney disease with multiple etiologies, including primary hyperoxaluria (PH), enteric hyperoxaluria, and ingestion of high-oxalate foods (eg, spinach, rhubarb, star fruit, and nuts) or supplements.

>> Research Summary: New Oral Manifestation of Primary Hyperoxaluria

However, the researchers noted that there have not been enough epidemiological studies to clarify whether there are further risk factors and associations. To fill this gap, Llanos and colleagues reported on 31 patients with native ON—including the cohort’s demographic and kidney biopsy characteristics, clinical course outcomes, and associated factors—from January 2015 to March 2023 at the Cleveland Clinic in Cleveland, Ohio.

Among the cohort, the mean age at diagnosis was 66.2 years, and more than half of the participants (58.1%) were women. Additionally, 87.1% had hypertension, 58.1% had diabetes, 42% had nephrolithiasis, and 77.4% had underlying CKD, with a mean baseline creatinine of 1.8 mg/dl ±1.3.

The cohort’s kidney biopsies showed a robust amount of calcium oxalate crystal deposits; the mean creatinine at biopsy was 5.2 mg/dl ±1.7. Further, 27 of 31 biopsies had additional diagnoses, the most common of which were acute tubular injury (n = 17) and diabetic glomerulosclerosis (n = 7). Severe and moderate interstitial fibrosis was present in 12 and 16 biopsies, respectively.

“In our cohort … the standout feature was the presence of a significant amount of interstitial fibrosis and tubular atrophy with over 90% of patients having at least moderate chronicity on kidney biopsy,” the authors wrote.

Examining the etiologies of ON among the cohort, 10 patients had a single etiology of ON, 10 had both enteric hyperoxaluria and high precursor intake, and 11 had an unclear etiology.

“Notably, only seven patients had a history of gastric bypass,” the authors wrote.

Looking at the cohort’s overall outcomes, the mean duration of follow-up was 26.8 months. A total of 26 patients had follow-up data longer than 1 year. Of these, 21 required dialysis and five were dialysis-free at presentation.

Of the 21 patients who needed dialysis, four died at 1 year. Further, 18 of the 21 patients who needed dialysis remained dialysis-dependent until last follow-up or death. While one patient recovered with residual CKD in this group, two patients received a kidney transplant.

In the dialysis-free cohort, one patient died at 1 year, while one patient recovered without residual CKD. One patient with PH underwent a combined liver-kidney transplant and was removed from dialysis at follow-up.

“These outcomes show an overall poor prognosis, but more importantly, demonstrate the need for early suspicion/screening for PH given its better prognosis and defined treatment strategy, thorough review of medications and supplements, as well as surgical history given the multifactorial nature of this condition,” the authors concluded.

Reference:
Llanos M, Kwon A, Herlitz L, et al. The clinical and pathological characteristics of patients with oxalate nephropathy. Kidney360. 2024;5(1):65-72. doi:10.34067/KID.0000000000000340