title: Progression of nephrolithiasis: long-term outcomes with observation of asymptomatic calculi.
abstract: OBJECTIVE
  Observation is often recommended for patients presenting with asymptomatic renal calculi. This study evaluated the natural history of asymptomatic calculi and the risk of progression of disease.
  
  
  METHODS
  We conducted a retrospective evaluation of 300 male patients average age 62.8 years who were followed for a mean of 3.26 years for asymptomatic renal calculi in an outpatient urology clinic. At presentation, the mean cumulative stone diameter was 10.8 mm; 56% were lower-pole stones, and 48% of the patients had multiple calculi. Patients underwent annual radiographic imaging and clinic visits with standardized questions regarding the development of symptoms or complications from calculi. Progression of disease was defined as the need for surgical intervention, the development of pain, or stone growth on serial imaging.
  
  
  RESULTS
  Overall, 77% of patients experienced disease progression, with 26% requiring surgical intervention. Stone size was positively associated with progression: those with an isolated stone >/=4 mm on presentation were 26% more likely to fail observation than patients with smaller solitary calculi (P = 0.012). Stone growth was less common in those with upper-pole and middle-pole stones (47% v 61%) for lower-pole stones; P = 0.002). Urine uric acid concentration correlated positively with the rate of stone growth (P = 0.05). Likewise, serum uric acid concentration predicted stone growth (odds ratio = 3.6).
  
  
  CONCLUSIONS
  Stratification of risk of progression according to presenting stone size, location, and composition may facilitate discussions with the patient regarding the alternatives of observation versus intervention. Specifically, small non-uric acid calculi in the upper pole may be most amenable to observation.
authors.affiliation: Department of Urologic Surgery and Department of Medicine, University of Minnesota, USA.
authors.forename: Abram
authors.initials: A
authors.lastname: Burgher
authors.forename: Mandi
authors.initials: M
authors.lastname: Beman
authors.forename: Jeremy L
authors.initials: JL
authors.lastname: Holtzman
authors.forename: Manoj
authors.initials: M
authors.lastname: Monga
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D005500:Follow-Up Studies; D006801:Humans; D007669:Kidney Calculi / Q000175:diagnosis*; D008875:Middle Aged; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D013997:Time Factors