Correlation between Urinary Oxalate Levels and Enteric Oxalobacter formigenes in Patients with Calcium Oxalate Urolithiasis / 대한비뇨기과학회지

ABSTRACT

PURPOSE: We performed a prospective study to evaluate the intestinal colonization by Oxalobacter formigenes, and its relationship to the levels of urinary oxalate in patients with calcium oxalate stone disease. MATERIALS AND METHODS: One hundred and three patients with calcium oxalate urolithiasis, with a mean age of 47 years, ranging in age from 21 to 73, followed-up between August 2000 and September 2001, were enrolled in this study. Fresh stool and 24-hour urine samples were performed. The genus specific oligonucleotide sequences, corresponding to homologous regions residing in the oxc gene, which encodes for oxalyl-coenzyme A decarboxylase, were designed. In order to quantify the presence of O. formigenes in clinical specimens, a quantitative-PCR-based assay system, utilizing a competitive DNA template as an internal standard, was developed. Measurements of the urine volume, pH, creatinine clearance, oxalate, calcium, magnesium, phosphate, citrate and uric acid were performed. RESULTS: The intestinal Oxalobacterium was detected by PCR in 45.6% of the patients with calcium oxalate stones. In the patients with stones, who tested negative for the Oxalobacterium, the average urinary oxalate level was 0.36mmol/day, compared to 0.29mmol/day for those patients testing positive (p<0.05). The mean colony forming unit per gram of stool in all the patients was 1.1x107 (0 to 4.1x108). The 24 h urine oxalate level was significantly decreased with the increasing level of O. formigenes colony forming units (r= 0.517, p<0.001). CONCLUSIONS: Our results support the concept that O. formigenes is important in maintaining oxalate homeostasis, and its absence from the gut increases the risk of calcium oxalate urolithiasis, via increases in the level of urinary oxalate.