Another question surrounding this subset of patients involves the primary factor responsible for the formation of calculi within the diverticula. Unfortunately, the literature has provided conflicting data on this issue. Some groups attribute stone formation to underlying metabolic abnormalities (Hsu, et al 1998). Other groups have not found any metabolic problems, instead concluding that impaired urinary drainage from the diverticulum primarily contributes calculus formation (Liatsikos, et al 2000). By prospectively obtaining urines on our caliceal diverticula patients, we hope that detailed metabolic analyses will allow us to conclude definitively whether metabolic abnormalities are prevalent in this population.