The Accuracy Study Of The Diagnosis Of Uric Acid Calculi By Helical Computed Tomography

Object:To evaluate the clinical value of helical computed tomography in the determination of uric acid calculi in vivo.Methods:Clinical date of 307 patients with calculi in our hospital from September 2016 to September 2018 were analyzed.Before treatment,all patients were arranged to undergo non-enhanced Helical computed tomography scan with the CT layer thickness set at5 mm and CT parameters set at 120 KV and 240-300 mA.Two urologist Measured the mean CT value(HuMean),the maximum CT value(HuMax)and the standard deviation CT value(HuStd)of the calculi at the soft tissue window by PACS,and determined the chemical composition of the calculi by infrared spectroscopy.The method of univariate ANOVA was used to compare the difference of HuMean,HuMax and HuStd in all kinds of calculus.The method of t-test was used to compare the differences of HuMean,HuMax and HuStd between uric acid calculi and non-uric acid calculi.The method of the receiver operating characteristic curve(ROC)was used to get the optimal parameters of the critical value,and evaluate the sensitivity,specificity,positive predictive value,negative predictive value,Youden index and area under the ROC curve for uric acid calculi by various parameters.Results:The results indicated that among 307 patients with calculi,93 were pure calculi and 214 were mixed calculi.There were 4 kinds of pure calculi with 43 cases uric acid calculi,2 cases calcium carbonate calculi,6 cases ammonium magnesium phosphate calculi and 42 cases calcium oxalate monohydrate calculi.There were 8 kinds of mixed calculi with 3 cases dicalcium phosphate dihydrate+calcium oxalate monohydrate calculi,4 cases ammonium magnesium phosphate+hydroxyapatite calculi,2 cases ammonium urate+calcium oxalate monohydrate calculi,15 cases uric acid+calcium oxalate monohydrate,58 cases calcium oxalate monohydrate+calcium oxalate dihydrate calculi,38 cases calcium oxalate monohydrate+hydroxyapatite calculi,92 cases calcium oxalate monohydrate+calcium oxalate dihydrate+hydroxyapatite calculi,2 case ammonium magnesium phosphate+ammonium urate+hydroxyapatite calculi.The results indicated that among 307 patients with calculi,43 were uric acid calculi and 264 werenon-uric acid calculi.The maximum transverse diameter range of the measured stones was 6.00-56.63 mm,the HuMean range was 301.32-1490.77 Hu,the HuMax range was431.00-1861.00 Hu,the HuStd range was 17.34-503.23 Hu.The HuMean,HuMax and HuStd of uric acid calculi was 455.88±75.98 Hu,580.58±105.36 Hu,54.26±27.90 Hu,respectively.The HuMean,HuMax and HuStd of non-uric acid calculi was904.92±246.57 Hu,1201.77±263.41 Hu,202.38±83.83 Hu,respectively.There were significant differences in HuMean,HuMax and HuStd between uric acid calculi patients and non-uric acid calculi patients(P < 0.05).According to the ROC curve,the optimal critical value was obtained.HuMean≦578Hu was used to determine uric acid calculi,with sensitivity of 97.67%,specificity of 92.05%,positive predictive value of66.67%,negative predictive value of 99.59%,Youden index of 0.90 and area under ROC curve of 0.97.HuMax≦827Hu was used to determine uric acid calculi,with sensitivity of97.67%,specificity of 91.29%,positive predictive value of 64.62%,negative predictive value of 99.59%,Youden index of 0.89,area under ROC curve of 0.98.HuStd≦85.9Hu was used to determine uric acid calculi,with sensitivity of 90.70%,specificity of 93.56%,positive predictive value of 69.64%,negative predictive value of 98.41%,Youden index of 0.84 and area under ROC curve of 0.97.With the combination of HuMean≦578Hu,HuMax≦827Hu,HuStd≦85.9Hu to judge uric acid calculi,the sensitivity,specificity,positive predictive value and negative predictive value was 88.5%,98.6%,90.2% and 98.3% respectively.Conclusion:HuMean,HuMax and HuStd can be used to distinguish uric acid calculi from non-uric acid calculi.According to the ROC curve,the optimal critical values of HuMean≦578Hu,HuMax≦827Hu,HuStd≦85.9Hu were obtained for the identification of uric acid calculi and non-uric acid calculi.The combination of the above methods with HuMean≦578Hu,HuMax≦827Hu,HuStd≦85.9Hu can also be applied to the determination of uric acid calculi.The positive predictive value can be increased to 95%.This method can predict uric acid calculi well and provide reference for clinical treatment.