Urinary oxalate excretion and its role in vulvar pain syndrome

This study was undertaken to determine the urinary oxalate excretion patterns in patients with vulvodynia compared with controls and to evaluate antioxalate therapy in women with vulvar pain syndrome (vulvodynia).

A total of 130 consecutive patients with vulvar pain syndrome and 23 volunteers without symptoms collected urine specimens for 24 hours; each voiding was saved in individual labeled containers and refrigerated. The specimens were analyzed individually for oxalate and calculated according to 24-hour concentration, volume, and peak oxalate by hour. A total of 59 patients were treated with low-oxalate diets and calcium citrate for 3 months and evaluated for objective relief of vulvar pain.

The 24-hour excretion of oxalate was almost identical in controls and vulvodynia patients. The total 24-hour excretion was directly proportional to the volume of urine excreted (p < 0.001). No significant differences were found in peak oxalate excretion (95% confidence intervals). The number of voidings was higher in the vulvodynia cohort (p < 0.02). The 59 women with elevated oxalate concentrations (> 1 mg/40 dl) were treated with an antioxalate regimen. Fourteen (24%) demonstrated an objective response, but only 6 (10%) could have pain-free sexual intercourse.

Urinary oxalates may be nonspecific irritants that aggravate vulvodynia; however, the role of oxalates as instigators is doubtful.