Risk factors for urolithiasis in patients with ankylosing spondylitis: a prospective case–control study

It has been reported that renal stone formation increased in patients with ankylosing spondylitis (AS). However, its reason remains unclear. The aim of this study was to evaluate serially the possible risk factors for renal stone formation in AS patients. Two groups consisted of AS patients with renal stone ( n = 30), AS patients without renal stone ( n = 30), and 20 healthy controls (HC) were included to the study. Parathyroid hormone, calcium, magnesium, phosphorus and immunoglobulin A levels and 24 h urine were evaluated at baseline, and three times monthly. Serum calcium levels were higher in AS patients with urolithiasis than those without at baseline and third-month evaluation (baseline: 9.53 ± 0.3 vs 9.32 ± 0.3 mg/dl; p