title: Prevalence and risk factors for urolithiasis in primary gout: is a reappraisal needed?
abstract: OBJECTIVE
  To assess the prevalence and risk factors for urolithiasis in primary gout.
  
  
  METHODS
  One hundred forty patients with primary gout were studied. Urolithiasis was defined as a history of urolithiasis, or nephrolithiasis detected via ultrasonography in patients with no previous record of urolithiasis. Patient age, duration of gout, presence of tophi, obesity, alcoholism, high blood pressure, diabetes, hyperlipidemia, family history of urolithiasis, daily urine output, uricemia, urine pH, FeNa, FeUrate, urine pH/FeUrate index, and daily urine excretion of urate, sodium, calcium and potassium were compared between lithiasic and non-lithiasic subjects.
  
  
  RESULTS
  Fifty-five (39%; 95% CI 31-47) patients had urolithiasis, of which 37 (26%) were diagnosed by clinical history and 18 (13%) by ultrasonography. Patients with a silent kidney stone diagnosed by ultrasound tended to have shorter evolution of gout. Aside from urinary H+ ion concentration (lithiasic subjects 5.17 +/- 3.9 microM/l; non-lithiasic subjects 3.80 +/- 3.01 microM/l; p = 0.02), no difference was found between lithiasic and non-lithiasic subjects for the other variables studied.
  
  
  CONCLUSIONS
  Ultrasonography increased the probability of diagnosing urolithiasis by 50%, meaning the prevalence of urolithiasis in gout is likely higher than previously reported. A higher urinary H+ ion concentration was the only variable associated with urolithiasis. Due to advances in diagnosis of gout and urolithiasis, as well as biochemical assays, the prevalence and risk factors for urolithiasis in gout require reassessment.
authors.affiliation: Unidad de Investigación en Epidemiología Clínica, HE CMN Ignacio García Tellez, Instituto Mexicano del Seguro Social, Mérida, Yucatán, México. nemegyei@hotmail.com
authors.forename: José
authors.initials: J
authors.lastname: Alvarez-Nemegyei
authors.forename: Martha
authors.initials: M
authors.lastname: Medina-Escobedo
authors.forename: Salha
authors.initials: S
authors.lastname: Villanueva-Jorge
authors.forename: Janitzia
authors.initials: J
authors.lastname: Vazquez-Mellado
mesh_terms: D000328:Adult; D005260:Female; D006073:Gout / Q000453:epidemiology*; D006801:Humans; D008297:Male; D008800:Mexico / Q000453:epidemiology; D008875:Middle Aged; D015995:Prevalence; D011522:Protons; D012307:Risk Factors; D014463:Ultrasonography; D014545:Urinary Calculi / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000652:urine; D014556:Urine
chemical_list: D011522:Protons