title: Prevalence of urolithiasis in asymptomatic adults: objective determination using low dose noncontrast computerized tomography.
abstract: OBJECTIVE
  The true prevalence of urolithiasis in asymptomatic adults is unknown. Unenhanced computerized tomography represents the gold standard for detection. We evaluated the prevalence and symptomatic incidence of urolithiasis in a large cohort of asymptomatic adults using noncontrast computerized tomography.
  
  
  METHODS
  Low dose noncontrast computerized tomography was performed in 5,047 consecutive asymptomatic adults (mean age 56.9 years, 2,747 women and 2,300 men) between 2004 and 2008. Presence, size and location of urinary calculi were recorded. Screening prevalence as well as the incidence of symptomatic stone disease during a 10-year interval (1997 to 2007) was compared against previously established clinical risk factors.
  
  
  RESULTS
  The screening prevalence of asymptomatic urolithiasis was 7.8% (395 of 5,047 adults) with an average of 2.1 stones per case (range 1 to 29) and a mean stone size of 3.0 mm (range 1 to 20). During a 10-year period 20.5% (81 of 395) of patients with stones (1.6% of entire screening cohort) had at least 1 symptomatic episode. Males were more likely to have urolithiasis than females (9.7% vs 6.3%, p <0.001). Diabetes (9.0% vs 7.7%, p = 0.45), obesity (7.6% vs 7.9%, p = 0.72) and age 60 years or older (8.0% vs 7.7%, p = 0.73) did not affect prevalence, but diabetes and obesity did correlate with symptom development (p <0.001 and p <0.05, respectively).
  
  
  CONCLUSIONS
  This objective population based assessment in a large asymptomatic cohort showed an 8% prevalence of urolithiasis. Most cases were unsuspected and remained asymptomatic. Although there was no correlation between asymptomatic urolithiasis and diabetes, obesity or older age, diabetes and obesity were associated with a higher incidence of symptoms over time.
authors.affiliation: University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53792-3252, USA.
authors.forename: Cody J
authors.initials: CJ
authors.lastname: Boyce
authors.forename: Perry J
authors.initials: PJ
authors.lastname: Pickhardt
authors.forename: Edward M
authors.initials: EM
authors.lastname: Lawrence
authors.forename: David H
authors.initials: DH
authors.lastname: Kim
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Bruce
mesh_terms: D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011829:Radiation Dosage; D012307:Risk Factors; D014057:Tomography, X-Ray Computed / Q000379:methods; D052878:Urolithiasis / Q000000981:diagnostic imaging* / Q000453:epidemiology*