title: Combining Mean and Standard Deviation of Hounsfield Unit Measurements from Preoperative CT Allows More Accurate Prediction of Urinary Stone Composition Than Mean Hounsfield Units Alone.
abstract: OBJECTIVE
  The mineral composition of a urinary stone may influence its surgical and medical treatment. Previous attempts at identifying stone composition based on mean Hounsfield Units (HUm) have had varied success. We aimed to evaluate the additional use of standard deviation of HU (HUsd) to more accurately predict stone composition.
  
  
  METHODS
  We identified patients from two centers who had undergone urinary stone treatment between 2006 and 2013 and had mineral stone analysis and a computed tomography (CT) available. HUm and HUsd of the stones were compared with ANOVA. Receiver operative characteristic analysis with area under the curve (AUC), Youden index, and likelihood ratio calculations were performed.
  
  
  RESULTS
  Data were available for 466 patients. The major components were calcium oxalate monohydrate (COM), uric acid, hydroxyapatite, struvite, brushite, cystine, and CO dihydrate (COD) in 41.4%, 19.3%, 12.4%, 7.5%, 5.8%, 5.4%, and 4.7% of patients, respectively. The HUm of UA and Br was significantly lower and higher than the HUm of any other stone type, respectively. HUm and HUsd were most accurate in predicting uric acid with an AUC of 0.969 and 0.851, respectively. The combined use of HUm and HUsd resulted in increased positive predictive value and higher likelihood ratios for identifying a stone's mineral composition for all stone types but COM.
  
  
  CONCLUSIONS
  To the best of our knowledge, this is the first report of CT data aiding in the prediction of brushite stone composition. Both HUm and HUsd can help predict stone composition and their combined use results in higher likelihood ratios influencing probability.
authors.affiliation: 1 Division of Urology, The University of Western Ontario , St-Joseph's Healthcare, London, Ontario, Canada .
authors.forename: Thomas
authors.initials: T
authors.lastname: Tailly
authors.affiliation: 2 Division of Urology, Lenox Hill Hospital , New York, New York.
authors.forename: Yaniv
authors.initials: Y
authors.lastname: Larish
authors.affiliation: 3 Department of Radiology, The University of Western Ontario , London, Ontario, Canada .
authors.forename: Brandon
authors.initials: B
authors.lastname: Nadeau
authors.affiliation: 1 Division of Urology, The University of Western Ontario , St-Joseph's Healthcare, London, Ontario, Canada .
authors.forename: Philippe
authors.initials: P
authors.lastname: Violette
authors.affiliation: 4 Division of Urology, Hackensack University Medical Center , Hackensack, New Jersey.
authors.forename: Leonard
authors.initials: L
authors.lastname: Glickman
authors.affiliation: 1 Division of Urology, The University of Western Ontario , St-Joseph's Healthcare, London, Ontario, Canada .
authors.forename: Daniel
authors.initials: D
authors.lastname: Olvera-Posada
authors.affiliation: 1 Division of Urology, The University of Western Ontario , St-Joseph's Healthcare, London, Ontario, Canada .
authors.forename: Husain
authors.initials: H
authors.lastname: Alenezi
authors.affiliation: 3 Department of Radiology, The University of Western Ontario , London, Ontario, Canada .
authors.forename: Justin
authors.initials: J
authors.lastname: Amann
authors.affiliation: 1 Division of Urology, The University of Western Ontario , St-Joseph's Healthcare, London, Ontario, Canada .
authors.forename: John
authors.initials: J
authors.lastname: Denstedt
authors.affiliation: 1 Division of Urology, The University of Western Ontario , St-Joseph's Healthcare, London, Ontario, Canada .
authors.forename: Hassan
authors.initials: H
authors.lastname: Razvi
mesh_terms: D000328:Adult; D019540:Area Under Curve; D002129:Calcium Oxalate / Q000737:chemistry; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012372:ROC Curve; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods; D014545:Urinary Calculi / Q000000981:diagnostic imaging*
chemical_list: D002129:Calcium Oxalate