T.05.4: RENAL LITHOGENIC RISK IN PATIENTS WITH INFLAMMATORY BOWEL DISEASES CORRELATES WITH MICROBIOTA COMPOSITION, URINARY PROFILE AND DIETARY INTAKE

Abstract Background Nephrolithiasis (NL) is a common extra-intestinal complication of inflammatory bowel diseases (IBD), often related to enteric hyperoxaluria. Growing evidence highlights the association between NL and gut microbiota, but no data are available on the urinary microbiota in IBD patients. Our study aims to analyse the relationship between diet, urinary lithogenic profile, and gut and urinary microbiota in patients with IBD. Methods We prospectively enrolled consecutive adult patients with IBD. All patients underwent abdominal ultrasound, blood tests and 24h-urine collection for lithogenic profile analysis. Moreover, a nutritional evaluation was performed, and all patients underwent bioimpedance measurement. Urinary and gut microbiota were analysed through 16S rRNA sequencing. Results 60 patients were enrolled: 32 with Crohn’s disease (CD) and 28 with ulcerative colitis (UC). NL was more frequent in CD than in UC (28% vs 14%). In patients with NL, gut microbiota analysis showed a lower relative abundance of Agathobacter (p<0.05) and a reduction in alpha diversity (p<0.05) [figure 1]. No statistically significant difference was found in urinary microbiota composition comparing patients with the presence or absence of NL. Protein (g/die) and phosphorus (mg/die) dietary intake were significantly associated with oxaluria (mg/L) (p=0.032 and p=0.007, respectively). At the same time, protein and calcium (mg/day) intake were significantly associated with NL (p= 0.018 and p= 0.023, respectively). Oxaluria and calcium oxalate relative saturation ratio (RSRCaOx) were significantly higher in CD compared to UC [Table 1]. Conclusion Patients with IBD and NL have distinctive gut microbiota features. CD patients showed a higher prevalence of NL and oxaluria levels than UC. In addition, NL occurrence and oxaluria correlated with some nutritional parameters. Further studies are needed to identify patients with IBD at greater risk of NL by connecting the parameters of the gut microbiota, urinary profile and dietary intake to act on modifiable factors aiming to reduce this risk.