title: Risk factors associated with renal lithiasis during uricosuric treatment of hyperuricemia in patients with gout.
abstract: OBJECTIVE
  To find factors associated with the development of renal colic during uricosuric therapy.
  
  
  METHODS
  We performed a prospective cohort followup study of patients with gout and no previous history of kidney stones who had been treated with uricosurics. Clearance of creatinine and urate, 24-hour urinary uric acid (UA), undissociated urinary UA concentration, 24-hour undissociated urinary UA, and pH and urine sediment were obtained. Cox proportional hazards regression analysis was used to identify variables associated with renal colic as the outcome. The rate of renal colic was compared with that of control patients receiving allopurinol who had no previous history of renal stones.
  
  
  RESULTS
  We analyzed a 784 patient-year exposure from 216 patients: 206 with renal underexcretion of UA and 10 with normal excretion. There were 21 clinical events. Two variables showed increased risk hazard for developing lithiasis: clearance of UA at baseline and undissociated urinary UA concentration during followup. When only patients with underexcretion of UA were included in the analysis, undissociated urinary UA during followup remained the only statistically significant variable. Patients who showed an undissociated UA concentration < 20 mg/dl did not show an increase in the rate of lithiasis or events compared with patients receiving allopurinol.
  
  
  CONCLUSIONS
  Clearance of UA at baseline may be useful for selecting patients suitable for uricosuric treatment. The estimation of the concentration of undissociated urinary UA is useful for evaluating the risk of lithiasis during followup.
authors.affiliation: Hospital de Cruces, Vizcaya, Spain. fernando.perezruiz@osakidetza.net
authors.forename: Fernando
authors.initials: F
authors.lastname: Perez-Ruiz
authors.forename: Samuel
authors.initials: S
authors.lastname: Hernandez-Baldizon
authors.forename: Ana M
authors.initials: AM
authors.lastname: Herrero-Beites
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Gonzalez-Gay
mesh_terms: D000493:Allopurinol / Q000009:adverse effects / Q000627:therapeutic use; D001553:Benzbromarone / Q000009:adverse effects / Q000627:therapeutic use; D015331:Cohort Studies; D003404:Creatinine / Q000652:urine; D005500:Follow-Up Studies; D006073:Gout / Q000150:complications / Q000188:drug therapy*; D006801:Humans; D033461:Hyperuricemia / Q000150:complications / Q000188:drug therapy*; D008875:Middle Aged; D016016:Proportional Hazards Models; D011446:Prospective Studies; D056844:Renal Colic / Q000209:etiology*; D012307:Risk Factors; D013997:Time Factors; D014527:Uric Acid / Q000652:urine; D014528:Uricosuric Agents / Q000009:adverse effects* / Q000627:therapeutic use; D052878:Urolithiasis / Q000139:chemically induced / Q000209:etiology*
chemical_list: D014528:Uricosuric Agents; D014527:Uric Acid; D001553:Benzbromarone; D000493:Allopurinol; D003404:Creatinine