title: Profile of the Ammonium Acid Urate Stone Former Based on a Large Contemporary Cohort.
abstract: OBJECTIVE
  To evaluate and profile ammonium acid urate (AAU) stone formers utilizing a large contemporary cohort.
  
  
  METHODS
  A retrospective review of all patients with documented AAU urolithiasis on stone analysis was performed from 1995 to 2013. A stone was considered AAU if it contained at least 10% of the total composition on stone analysis.
  
  
  RESULTS
  Of 12,421 stones, a total of 111 AAU stones were identified in 89 patients. Seventy-two patients (81%) had mixed composition stones. Of the 89 AAU patients, 10 (11%) had chronic kidney disease, 12 (13%) had recurrent urinary tract infections, 8 (9%) had diabetes mellitus, 25 (28%) had a history of ileostomy or bowel resection, and 11 (12%) had significant diarrhea or inflammatory bowel disease. Additionally, 20 (22%) had prior prostate surgery with bladder neck contracture and 8 (9%) were managed with a chronic indwelling catheter. Surgical intervention was required in 74 patients (83%). At the median follow-up of 4.9 years, 19 patients (21%) had stone recurrence with a median time to recurrence of 22 months (interquartile range: 10.5-42.0).
  
  
  CONCLUSIONS
  AAU stones are rare. In addition to previously described risk factors for AAU stone formation, patients with prior prostate surgery and bladder neck contracture or a surgically altered bladder may be at increased risk for formation. Furthermore, the long-term follow-up provided by this large AAU cohort demonstrates a significant risk for stone recurrence.
authors: Department of Urology, Mayo Clinic, Rochester, MN.
authors: Derek J
authors: DJ
authors: Lomas
authors: Department of Urology, Mayo Clinic, Rochester, MN.
authors: Christopher D
authors: CD
authors: Jaeger
authors: Department of Urology, Mayo Clinic, Rochester, MN. Electronic address: gecoots2@gmail.com.
authors: Amy E
authors: AE
authors: Krambeck
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014527:Uric Acid / Q000032:analysis*; D014545:Urinary Calculi / Q000737:chemistry*
chemical_list: D014527:Uric Acid