Renal involvement in ankylosing spondylitis: a retrospective, population-based cohort study using data from the...

Renal involvement in ankylosing spondylitis (AS) is recognised but understudied, with heterogeneous reports ranging from urinalysis abnormalities to end-stage disease and malignancy. Robust, contemporary and population-level estimates remain lacking.

To quantify the burden and risk of major nephrological outcomes in AS versus matched controls, estimate long-term occurrence, and explore sex-specific differences.

We performed a retrospective, population-based cohort study using the TriNetX Global Collaborative Network of anonymised electronic health records. Adults with AS were compared 1:1 with controls using propensity score matching across demographic factors and relevant comorbidities. The primary renal outcome was chronic kidney disease (CKD), while the secondary outcomes were as follows: acute kidney injury (AKI), dialysis initiation, glomerular diseases, tubulointerstitial nephropathies, proteinuria, haematuria, urolithiasis, nephrological neoplasms and kidney transplantation. Time-to-event analyses used Cox models; robustness was assessed in prespecified sensitivity analyses.

After matching, AS was associated with markedly higher hazards across the full spectrum of renal outcomes. The risk of developing CKD (primary outcome) was more than twofold higher in the AS cohort (HR 2.51; 95% CI 2.21 to 2.84). Among secondary outcomes, the highest risk was observed for dialysis initiation (HR 7.58; 95% CI 6.19 to 9.27), followed by AKI (HR 2.18; 95% CI 2.03 to 2.35) and glomerular diseases (HR 2.06; 95% CI 1.71 to 2.49). Associations were consistent across prespecified sensitivity analyses.

AS confers a broad, multifactorial increase in renal morbidity. These findings support routine nephrological surveillance within rheumatology pathways. A multidisciplinary approach is warranted to enable earlier detection and mitigate irreversible kidney injury.