title: Natural history of asymptomatic renal stones and prediction of stone related events.
abstract: OBJECTIVE
  The appropriate management for asymptomatic renal stones remains unclear. We assessed the natural history and progression rate of such stones and identified clinical factors associated with an increased risk of stone related events.
  
  
  METHODS
  We retrospectively reviewed the medical records of 201 male and 146 female patients with asymptomatic renal stones. It was recommended that patients be followed every 6 months. Mean followup was 31 months (range 6 to 180). Patients were divided into 2 groups by stone related events, including spontaneous stone passage, flank pain, stone growth or the need for intervention during followup.
  
  
  RESULTS
  Spontaneous passage occurred in 101 patients (29.1%). Of the patients 186 (53.6%) and 161 (46.4%) did and did not have stone related events, respectively. Of the whole cohort 85 patients (24.5%) required intervention but only 4.6% needed surgery. At 19 months after diagnosis 50% of the patients had a symptom. Those with stone related events were more likely to be younger (mean ± SD age 46.6 ± 12.7 vs 49.3 ± 12.6 years) and male, and have a stone history (p = 0.047, 0.017 and 0.014, respectively). Male gender significantly decreased the probability of freedom from stone related events (log rank test p = 0.0135) and it was an independent predictor of stone related events (HR 1.521, p = 0.009). Younger patients, and those with smaller stones and no stone growth were more likely to experience spontaneous passage and less likely to undergo intervention (each p <0.05).
  
  
  CONCLUSIONS
  Asymptomatic renal stones can be followed safely but long-term followup is necessary. Periodic followup and early intervention should be recommended in patients with risk factors.
authors.affiliation: Department of Urology, College of Medicine, Chungbuk National University, Cheongju, Republic of Korea.
authors.forename: Ho Won
authors.initials: HW
authors.lastname: Kang
authors.forename: Sang Keun
authors.initials: SK
authors.lastname: Lee
authors.forename: Won Tae
authors.initials: WT
authors.lastname: Kim
authors.forename: Yong-June
authors.initials: YJ
authors.lastname: Kim
authors.forename: Seok-Joong
authors.initials: SJ
authors.lastname: Yun
authors.forename: Sang-Cheol
authors.initials: SC
authors.lastname: Lee
authors.forename: Wun-Jae
authors.initials: WJ
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D058070:Asymptomatic Diseases; D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000150:complications* / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012189:Retrospective Studies; D012307:Risk Factors; D055815:Young Adult