title: Annual changes of the incidence and clinical characteristics of magnesium ammonium phosphate urinary stones.
abstract: BACKGROUND
  Magnesium ammonium phosphate (MAP) urinary stones account for the majority of staghorn stones and frequently cause a non-functioning kidney. In the present study, we examined the annual changes of the number and clinical characteristics of MAP stones.
  
  
  METHODS
  The annual incidence of MAP stones was investigated in 2619 patients with urinary stones in whom composition of the stone was analysed at Chiba University Hospital between 1964 and 1999. In addition, the annual number of patients with MAP stones was examined at Funabashi Clinic. In a total of 644 patients with MAP stones, age and sex of the patients, location and size of the MAP stones, urinary cultures and etiological factors were analysed.
  
  
  RESULTS
  The number of MAP stones in the lower urinary tract was relatively constant. In contrast, MAP stones in the upper urinary tract had dramatically decreased since 1989, resulting in an increase in the rate of MAP stones in the lower urinary tract. Age distribution of the MAP stone patients ranged from 10 years to > 80 years, with the majority aged 30-60 years. The proportion of larger MAP stones in the upper urinary tract increased. There was no significant difference in prevalence of urine cultures. Among etiological factors for MAP stones, difficulty on urination tended to be common in recent years.
  
  
  CONCLUSIONS
  The number of MAP stones, especially in upper urinary tract, has been decreasing during the last decade. At present, treatment of urinary tract obstruction seems important for the management of MAP stones in lower urinary tract.
authors.affiliation: Department of Urology, Graduate School of Medicine, Chiba University, Japan.
authors.forename: Takahide
authors.initials: T
authors.lastname: Ogata
authors.forename: Koichiro
authors.initials: K
authors.lastname: Akakura
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Mizoguchi
authors.forename: Kazuo
authors.initials: K
authors.lastname: Mikami
authors.forename: Kuniyoshi
authors.initials: K
authors.lastname: Nozumi
authors.forename: Haruo
authors.initials: H
authors.lastname: Ito
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D005260:Female; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D017616:Magnesium Compounds / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D013997:Time Factors; D014545:Urinary Calculi / Q000737:chemistry* / Q000453:epidemiology*; D014555:Urination Disorders / Q000453:epidemiology
chemical_list: D017616:Magnesium Compounds