Are there seasonal variations in renal colic in uric acid stone formers in Germany?

Purpose Seasonal variations in renal colic have been described by many authors for different countries worldwide. In most studies, there was no differentiation with regard to stone composition. Recently, we demonstrated that there was no seasonal variation in renal colic and urine chemistry for calcium oxalate stone formers in Germany. As we have many uric acid stone formers (UASFs) in our region, we were interested in learning the situation of this type of stone. Methods We studied 286 consecutive UASFs with symptoms of renal colic. We divided them into four groups according to the quarters of the year. For stone analysis, X-ray diffraction/polarizing microscopy was used. Additionally, the following general parameters were examined in all patients: age, BMI, blood pressure, stone frequency, diabetes mellitus; blood: creatinine, glucose, uric acid, calcium, sodium and potassium; urine: pH, volume, calcium, uric acid, citrate, ammonia, and urea. Using the statistical program Prism 5 (GraphPad Software, San Diego, USA), significant differences between the four groups were calculated by the Kruskal-Wallis test. Results We observed significantly more UASFs with renal colic in the third and fourth quarters of the year. This is in contrast to our findings in calcium oxalate patients. However, there was no variation in metabolic parameters. Conclusion The reasons are unclear; different temperatures are not a sufficient explanation, as one quarter is in the warm season and the other one is in the cold season. Unfortunately, no data have been reported in the literature thus far. Further studies are required to better understand these findings.