title: The success of extracorporeal shock-wave lithotripsy based on the stone-attenuation value from non-contrast computed tomography.
abstract: OBJECTIVE
  To determine the utility of the urinary stone-attenuation value (SAV, in Hounsfield units, HU) from non-contrast computed tomography (NCCT) for predicting the success of extracorporeal shock-wave lithotripsy (ESWL).
  
  
  METHODS
  The study included 305 patients with renal calculi of ⩽30 mm and upper ureteric calculi of ⩽20 mm. The SAV was measured using NCCT. Numerical variables were compared using a one-way analysis of variance with posthoc multiple two-group comparisons. Univariate and multivariate regression analysis models were used to test the preferential effect of the independent variable(s) on the success of ESWL.
  
  
  RESULTS
  Patients were grouped according to the SAV as group 1 (⩽500 HU, 81 patients), group 2 (501-1000 HU, 141 patients) and group 3 (>1000 HU, 83 patients). ESWL was successful in 253 patients (83%). The rate of stone clearance was 100% in group 1, 95.7% (135/141) in group 2 and 44.6% (37/83) in group 3 (P = 0.001).
  
  
  CONCLUSIONS
  The SAV value is an independent predictor of the success of ESWL and a useful tool for planning stone treatment. Patients with a SAV ⩾956 HU are not ideal candidates for ESWL. The inclusion criteria for ESWL of stones with a SAV <500 HU can be expanded with regard to stone size, site, age, renal function and coagulation profile. In patients with a SAV of 500-1000 HU, factors like a body mass index of >30 kg/m(2) and a lower calyceal location make them less ideal for ESWL.
authors.affiliation: Department of Urology, Faculty of Medicine, Beni Suef University, Beni Suef, Egypt.
authors.forename: Amr M
authors.initials: AM
authors.lastname: Massoud
authors.affiliation: Department of Urology, Faculty of Medicine, Beni Suef University, Beni Suef, Egypt.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Abdelbary
authors.affiliation: Department of Urology, Faculty of Medicine, Beni Suef University, Beni Suef, Egypt.
authors.forename: Ahmad A
authors.initials: AA
authors.lastname: Al-Dessoukey
authors.affiliation: Department of Urology, Faculty of Medicine, Beni Suef University, Beni Suef, Egypt.
authors.forename: Ayman S
authors.initials: AS
authors.lastname: Moussa
authors.affiliation: Theodor Bilharz Research Institute, Cairo, Egypt.
authors.forename: Ahmed S
authors.initials: AS
authors.lastname: Zayed
authors.affiliation: Department of Urology, Faculty of Medicine, Beni Suef University, Beni Suef, Egypt.
authors.forename: Osama
authors.initials: O
authors.lastname: Mahmmoud
keywords: BMI; BMI, body mass index; ESWL; HU, Hounsfield unit; Lower calyceal stone; NCCT, non-contrast computed tomography; ROC, receiver operating characteristic (curve); SAV, stone-attenuation value; Stone attenuation value; US, ultrasonography; Urinary calculi