Circulating Oxalate Levels in Short Bowel Syndrome as a Severity Marker of CKD

Abstract

BackgroundPatients with short bowel syndrome (SBS) may exhibit enteric hyperoxaluria (EH), and the prevalence of oxalate nephropathy in SBS is likely underestimated. Plasma oxalate (POx) is a surrogate of systemic oxalate deposition and, consequently, may increase the risk of developing chronic kidney disease (CKD). The main objective was to explore the distribution of plasma oxalate levels in SBS patients. MethodsPatients followed for SBS were recruited prospectively in the OXAGO study (NCT04119765) to assess POx during their annual renal follow-up including iohexol clearance. Inclusion criteria were age ≥ 18 years, and SBS type II and type III for more than 6 months. ResultsForty-seven patients were included but only 45 patients has a measured Pox (55 % males, 80 % SBS type 2, 66 % parenteral nutrition, 61% kidney stone history). POx levels were 6.8±4.4 μmol/L, 29 % of patients had POx ≥5 μmol/L. In the whole cohort, mean urinary oxalate (UOx) was 648 ± 415 and 54 % were > 500 μmol/24hrs. In the group of patients with high POx levels (HPO), 24hr-urine oxalate was significantly higher than in the group with normal POx levels (NPO): 919±566 vs 526±257 μmol/L, p=0.003.GFR was 66±22 mL/min/1.73m2, 91% had CKD. GFR was significantly lower in the HPO than in the NPO group: 49±23 vs 73±18 mL/min/1.73m2, p=0.0005. ConclusionPatients with SBS can display increased POx levels even with GFR > 30 mL/min per 1.73m2. POx may be an interesting biomarker to assess the severity of enteric hyperoxaluria.