Ureteral Calculi Detection Using Low Dose Computerized Tomography Protocols is Compromised in Overweight and Underweight Patients

• Published in: The Journal of urology Vol. 188; no. 1; pp. 124 - 129
• Main Authors: Heldt, Jonathan P, Smith, Jason C, Anderson, Kirk M, Richards, Gideon D, Agarwal, Gautum, Smith, Damien L, Schlaifer, Amy, Pittenger, Nicholas T, Han, Daniel S, Baldwin, Brenton D, Schroeder, Gabriel T, Baldwin, D. Duane
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.07.2012; Elsevier
• Subjects: Biological and medical sciences; Body Weight; Cadaver; Cadavers; Calcium oxalate; Computed tomography; diagnostic imaging; Humans; Medical sciences; Metabolic diseases; nephrolithiasis; Nephrology. Urinary tract diseases; Obesity; Overweight - complications; Radiation; Radiation Dosage; Reproducibility of Results; ROC Curve; Thinness - complications; tomography; Tomography, X-Ray Computed; Underweight; ureteral calculi; Ureteral Calculi - complications; Ureteral Calculi - diagnostic imaging; Urinary lithiasis; Urinary tract; Urology; x-ray computed; radiation dosage; body mass index; diagnostic imaging; CT; mSv; ureteral calculi; millisievert; tomography; x-ray computed; nephrolithiasis; computerized tomography; milliampere-seconds; mAs; BMI; Ureteral lithiasis; Nephrology; Ureteral disease; X ray; Urology; Overweight; Tomography; Diagnosis; Kidney disease; Human; Urinary system disease; Radiodiagnosis; Low dose; Exploration; Urinary tract disease; Urinary stone; Radiography; Renal lithiasis; Medical imagery; Computerized axial tomography
• ISSN: 0022-5347; 1527-3792
• DOI: 10.1016/j.juro.2012.02.2568

Purpose Low dose computerized tomography protocols have demonstrated a reduction in radiation exposure while maintaining excellent sensitivity and specificity in the detection of stones in patients of average size. Low dose computerized tomography protocols have not yet been evaluated in subjects in the extremes of weight. We evaluated the effect of body weight when using low dose protocols to detect ureteral calculi. Materials and Methods Three cadavers of increasing weight (55, 85 and 115 kg) were prepared by inserting 721 calcium oxalate stones (range 3 to 7 mm) in 33 random configurations into urinary tracts. Cadavers were then scanned using a GE LightSpeed® at 7 radiation settings. An independent, blinded review by a radiologist was conducted to generate ROC curves, with areas under the curve compared using a 1-way ANOVA (α = 0.05). Results Sensitivity and specificity were significantly lower in the low and high weight cadavers compared to the medium weight cadaver at 5 mAs (p <0.001) and 7.5 mAs (p = 0.048). Differences in sensitivity and specificity at radiation settings of 15 mAs or greater were not significant. Conclusions The sensitivity and specificity for the detection of ureteral calculi on computerized tomography were decreased for underweight and overweight subjects when using extremely low dose radiation settings (less than 1 mSv). Low dose protocols of 15 mAs (2 mSv) can still be used for these subjects without jeopardizing the ability to identify ureteral stones.