title: Profile of metabolic and infectious stone-formers in a contemporary PCNL cohort.
abstract: BACKGROUND
  To identify factors associated with stone composition in patients undergoing percutaneous nephrolithotomy (PCNL).
  
  
  METHODS
  A retrospective analysis of patients who underwent PCNL at two academic institutions between 2002 and 2014. Stone composition, stone characteristics based on non-contrast computer tomography (NCCT), patient demographics, and the S.T.O.N.E nephrolithometry scores were compared. Stones were characterized as either infection or metabolic. Metabolic stones were classified as calcium phosphate-containing and all others.
  
  
  RESULTS
  A total of 192 renal units underwent PCNL. Retrieved stones were found to be 75% (144) metabolic and 25% (48) infection by stone analysis. Of the metabolic stones, 51% (73) were phosphate-containing calculi. Overall, infection stones were found to have a significantly higher S.T.O.N.E nephrolithometry score than metabolic stones (9.2 versus 8.1, p < 0.001). Average Hounsfield units (HU) were significantly lower in infection stones (765 versus 899, p < 0.05). Sixty-three percent of patients with infection stones were female as compared to 46% of patients with metabolic stones. Patients with phosphate-containing stones in the metabolic group were significantly more likely to be female (56% versus 35%, p < 0.01), younger (mean 49 versus 60 years of age, p < 0.02), and have lower BMI's (30 versus 32, p < 0.02) compared with other metabolic stones.
  
  
  CONCLUSIONS
  Patient demographics including age, sex and BMI differ between patients with phosphate and non-phosphate containing metabolic stones. Higher S.T.O.N.E nephrolithometry scores were found in infection stones. These findings may serve as useful tools in the identification of stone compositions that are being seen more frequently in large and complicated stones undergoing PCNL.
authors.affiliation: University of Vermont Medical Center, Burlington, Vermont, USA.
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: King
authors.forename: Caleb J
authors.initials: CJ
authors.lastname: Seufert
authors.forename: Zhamshid
authors.initials: Z
authors.lastname: Okhunov
authors.forename: Nazih
authors.initials: N
authors.lastname: Khater
authors.forename: D Duane
authors.initials: DD
authors.lastname: Baldwin
authors.forename: Peter W
authors.initials: PW
authors.lastname: Callas
authors.forename: Kevan M
authors.initials: KM
authors.lastname: Sternberg
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D015992:Body Mass Index; D002130:Calcium Phosphates / Q000032:analysis*; D005260:Female; D006801:Humans; D007239:Infections / Q000150:complications; D007669:Kidney Calculi / Q000737:chemistry* / Q000145:classification / Q000000981:diagnostic imaging* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D009403:Nephrostomy, Percutaneous; D012189:Retrospective Studies; D012720:Severity of Illness Index; D012737:Sex Factors; D014057:Tomography, X-Ray Computed
chemical_list: D002130:Calcium Phosphates; C020243:calcium phosphate