OP07 Absolute and relative risks of kidney and urological complications in patients with Inflammatory Bowel Disease

Abstract Background Kidney-related complications are considered relatively common extraintestinal manifestations of inflammatory bowel disease (IBD), but absolute risks are not well characterized. We aimed at providing a comprehensive characterization of the burden of kidney-related complications in people with incident IBD by analysing issued clinical diagnoses and trajectories of estimated glomerular filtration rate (eGFR) in the complete population of Stockholm, Sweden. Methods We included 1,682,795 participants aged 11 or older, free from IBD or chronic kidney disease (CKD) diagnosis and who had a measurement of eGFR during 2006-2018. We analysed the association between developing IBD (time-varying exposure) and the risk of receiving a CKD diagnosis, acute kidney injury (AKI), kidney stones, or secondary amyloidosis, and experiencing the composite of declining their eGFR at least 30% from baseline or kidney failure (collectively termed as CKD progression). Absolute risks were calculated at 5- and 10-year of follow-up, and relative risks were calculated with Cox regression. We compared kidney-related risks overall and for Crohn’s disease (CD) and ulcerative colitis (UC) separately. Results After median 9 years, 10,117 participants newly developed IBD. Their mean age was 45 years. Compared with non-IBD periods, developing IBD associated with higher relative risks: the HR (95% CI) for the risk of receiving a CKD diagnosis was 1.24 (1.10-1.40), 1.11 (1.00-1.24) for the risk of CKD progression, and 1.25 (1.14-1.36) for the composite outcome of these two events. Within 10 years from IBD diagnosis, 6.4% (5.8-7.0%) of participants received a diagnosis of CKD, but 11.4% (10.4-12.4%) had a clinically relevant reduction in eGFR. The risks of AKI (HR 1.97 [1.70-2.29]; 10-y absolute risk 3.6%), kidney stones (HR 1.69 [1.48-1.93]; 10-y risk 5.6%) and secondary amyloidosis (HR 2.77 [1.44-5.35]; 10-y risk 0.2%) were also higher in persons developing IBD compared to non-IBD periods. In general, CD patients exhibited higher absolute and relative kidney risks than UC patients. Conclusion One in ten persons with IBD develop chronic kidney disease within 10 years from diagnosis, with many of these events not being identified through diagnostic codes. This, together with higher risks of AKI and kidney stones emphasizes the need for monitoring of kidney function and established protocols for referral to nephrological/urological care.