To evaluate the prevalence and causes of isolated microscopic hematuria in patients with rheumatoid arthritis (RA).
An unselected population of 1018 patients with RA (810 women, 208 men) were studied prospectively (n = 604) or retrospectively (n = 414), and the results were compared with an age and sex matched control population (n = 457; 352 women, 105 men). Hematuria was defined as a positive dipstick result in 2 urine samples, and was regarded as isolated when no concomitant proteinuria was found (urine protein excretion < or = 0.15 g/24 h). To investigate the urological causes of isolated hematuria, urine cytology, renal ultrasound, and urethrocystoscopy were undertaken. Renal biopsy was performed when no urological lesions were found.
There was no difference in the prevalence of isolated hematuria between patients with RA and controls (women 10 and 9%, men 5 and 6%, respectively; total 9% for both). Mild mesangial glomerulopathy was the most common renal biopsy finding in patients with RA with isolated hematuria, found in 13 of 15 adequate renal biopsy specimens. The cause of hematuria remained uncertain or unknown in 52% of the patients with RA and in 61% of controls.
The prevalence of isolated microscopic hematuria was not significantly more frequent in patients with RA than in age and sex matched controls. This result was independent of the definition or grade of hematuria. Mesangial glomerulopathy was the most common renal biopsy finding in patients with RA with isolated hematuria.