Objective: To determine the frequency of hypercalciuria and renal stones in ankylosing spondylitis (AS) sufferers.
Methods: This study involved 83 consecutive AS patients (21 female, 62 male; mean age 36.7 yr), 72 consecutive Behcet's disease (BD) patients (29 female, 43 male; mean age 37.7 yr) as disease control and 92 healthy control (HC) (26 female, 66 male; mean age 32.9 yr.) Twenty-four hour urine analyses for urinary calcium and uric acid levels were performed in each patient. Likewise, blood samples for erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), parathyroid hormone (PTH), calcium and uric acid evaluation were taken. Renal ultrasonography to evaluate the presence of renal stone was performed in patients with AS, as well as in the BD patients and HC individuals after a fasting period of 12 hours.
Results: 20 of the 80 (25%) patients with AS were diagnosed with renal stones. Only 4/72 (5.5%) BD patients, and 3/98 (3.3%) HC individuals had renal stones by ultrasonography. AS patients had a significantly higher frequency of renal stones compared with BD (p < 0.001) and HC (p < 0.0001). AS patients with renal stones were much older and their disease duration was much longer in comparison with AS patients without renal stones. Ultrasonographic and laboratory findings did not correlate. The number of AS patients with hypercalciuria who had renal stones was higher than that of AS patients who did not have renal stones (p < 0.01). There was a negative correlation between acute phase response and spinal mobility.
Conclusion: Renal stone prevalence was found to increase in AS patients. The likelihood of renal stone formation was also found to increase with the extension of the disease duration of AS sufferers.