CRP and urinary tract obstruction: Receiver operative characteristic analysis revealed that WBCC (area under the curve [AUC] = 0.713), history of urological surgery (AUC = 0.713), serum CRP (AUC = 0.712), and HU value of hydronephrosis (AUC = 0.613) had a good ability to predict pyonephrosis in patients with UTS (Fig. 2).The sensitivity and specificity of the HU value in predicting COP were 71.4% and 70.2%, respectively; the optimal cut-off value was 9.5.