High Plasma Oxalate in Short Bowel Syndrome: Never Forget the Risk of Oxalate Nephropathy (oxago Study)

Rationale: We aimed to explore the distribution of plasma oxalate (Pox) in enteric hyperoxaluria for short bowel syndrome patients (SBS) to estimate the severity of enteric hyperoxaluria. Methods: Forty seven participants were recruited prospectively from nutrition unit. Inclusion criteria were age ≥ 18 years, type II or type III short bowel > 6 months. Plasma oxalate was measured during their annual follow up. Factor risk identifications and statistics. Approved study NCT04119765. Results: Mean age was 60.5 ± 15.3 years old, 55 % male, 80 % type 2 SBS, median time (min-max) from SBS surgery of 72 (10-120) months, 66 % with parenteral nutrition and 61 % with history of kidney stone. Among all patients, 29 % of patients had a plasma oxalate ≥ 5 μmol/L (normal < 5 μmol/L) with a mean of 11.5 ± 6.1 μmol/L. In the group of patients with elevated plasma oxalate (EPO), 24hrs urine oxalate was significantly higher (919 ± 566 μmol/24hrs) vs normal plasma oxalate group (526 ± 257 μmol/24hrs), p=0.003. Measured GFR (mGFR) was 66 ± 22 mL/min/1.73m2, most of them displayed a chronic kidney disease (91%). Mean mGFR was significantly lower in the EPO group (49 ± 23 mL/min/1.73m2 vs 73 ± 18 mL/min/1.73m2, p=0.005). The remaining small bowel length was not different between groups (77 ± 33 vs 91 ± 43 cm, p=0.3) however the percentage of remaining colon has a trend to be higher in the EPO group (82 ± 14 vs 67 ± 30, p=0.08 ). We found no difference in duration of SBS, plasma vitamin C and vitamin B6 level between groups. Urine oxalate was significantly higher in the group with sugar malabsorption (D-Xylose 60 min < 0.73 mmol/L), p=0.0063. Conclusion: We confirm SBS II or III patients are at high risk of nephrolithiasis. They can have an early increase of plasma oxalate, even with a eGFR > 30 mL/min/1.73m2. Plasma oxalate could be an interesting biomarker in these patients, especially to detect earlier oxalate nephropathy. Disclosure of Interest: None declared