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Kidney Week

Abstract: PO2533

Kidney Transplant Outcomes for Patients with Enteric Oxalosis

Session Information

Category: Transplantation

  • 1902 Transplantation: Clinical

Authors

  • Keddis, Mira T., Mayo Foundation for Medical Education and Research, Scottsdale, Arizona, United States
  • Grujic, Danica, Mayo Foundation for Medical Education and Research, Scottsdale, Arizona, United States
  • Kausz, Annamaria T., Mayo Foundation for Medical Education and Research, Scottsdale, Arizona, United States
Background

Patients with enteric disorders associated with hyperoxaluria and systemic oxalate burden (enteric oxalosis) are at increased risk for calcium oxalate deposition causing ESRD. The objective of this study is to evaluate kidney transplant (KTx) recipients with enteric oxalosis at our institution.

Methods

KTx recipients with suspected oxalosis due to any of the following: inflammatory bowel disease, bariatric surgery, or pancreatic insufficiency from 2015 to 2019 were included. At our institution, pre-KTx serum oxalate>30mcmol/L is the threshold for treatment.

Results

31 patients were identified. Mean age was 58.5 years, 55% were female, 81% white, and 94% first KTx. Most common cause of ESRD was diabetes (45%), and 84% were on dialysis prior to KTx (median 30.5 months). The most common enteric cause was Roux-en-Y gastric bypass (RYGB, 77%) with surgery 11 years (median) prior to KTx. 39% had history of nephrolithiasis. Median peak serum oxalate (SOx) pre-KTx was 24mcmol/L. 87% received deceased donor KTx and 52% had delayed graft function (DGF). Post-KTx, 36% received calcium with meals for oxalate binding, and 39% had low oxalate diet education. 5 patients had pre-KTx SOx >30mcmol/L at the time of KTx, of whom 4 had DGF and required either longer dialysis (up to 5 hours long) or increased dialysis sessions (up to 6 per week) to reduce SOx levels post-KTx. The median duration of dialysis after KTx was 13.5days. After median follow up of 27months, mean (SD) estimated glomerular filtration rate (GFR) was 47.6 ±21.7mL/min/1.73m2 and 68% of patients had GFR <60. One-year GFR was 48.4±21.4mL/min/1.73m2 which is lower than expected 1-year GFR for our Transplant Center (mean GFR 58.9 ±20.6ml/min/1.73m2). RYGB patients (n=24) had lower GFR vs patients with other EH causes (n=7) (1 year: 48.7±20.4 vs 56.7±4.9; last follow-up 47.3±21.1 vs 57.5±14.8 mL/min/1.73m2). Only 2 patients had oxalate crystals on protocol allograft biopsy, both with RYGB, and one with DGF and died 22 months after KTx. GFR at 1 year was 34±2.83 ml/min/1.73m2 for these 2 patients.

Conclusion

RYGB is the most common cause of enteric oxalosis in KTx recipients. DGF is common and graft outcomes are inferior compared to deceased donor KTx at our institution. The lower GFR in RYGB patients raise concern for enteric hyperoxaluria as an unrecognized risk for allograft dysfunction.

Funding

  • Commercial Support