目的 评价能谱CT成像各功能参数在肾积脓和肾积水鉴别方面的临床应用价值。 方法 回顾性分析2021年2月至2023年3月于重庆市南川区人民医院泌尿外科行能谱CT扫描的中重度肾积液患者共46例，包括18例肾积脓患者和28例肾积水患者，所有患者均于增强CT肾内积液显影时间段内行宝石能谱CT双能量能谱成像（gemstone spectral imaging，GSI）模式扫描，在后处理工作站及GSI浏览器获取患者肾积水液区的能谱CT 40~140 keV各层面下单光子能量图像、能谱衰减曲线、尿无机物定量及有效原子序数等特征参数图像；由公式k=（HU40/HU100）/60计算其能谱曲线斜率，对比以上参数差异。同时纳入肾积脓白细胞定量、肾积脓钙定量同能谱40 keV单能量图像上CT值的多元线性回归分析，并将所得数据均进行独立样本t检验，绘制ROC曲线对比各参数对肾积脓和肾积水鉴别上的敏感性和特异性。本研究拟通过以上相关参数以确定能谱CT在二者间的诊断效能。 结果 能谱CT显示肾积脓液区在40~60 keV的3个低能量层面能谱CT值差异有统计学意义，且能量越低（40 keV）差异性越大；肾积脓组的能谱曲线斜率、有效原子序数值、噪声比数值高于肾积水组，钙离子定量低于肾积水组，差异有统计学意义；肾积脓混合能量CT值略大于肾积水CT值，差异无统计学意义。根据能谱CT单能量图像和术后肾盂尿钙离子定量对患者肾积脓程度的多因素线性回归分析，肾盂脓尿白细胞个数（b=0.886，β=0.725，P<0.001）和肾盂脓尿钙定量（b=-75.037，β=-0.193，P=0.043）能够分别正向、负向预测能谱40 keV单能量图像上脓尿液区的CT值，并共同证实了对肾积脓诊断64.8%的预测率。ROC曲线分析表示脓尿中白细胞定量、40 keV单能量图像液性暗区的CT值、噪声比及脓尿钙离子相对定量均具有对肾积脓诊断效能，且预测效果较好。 结论 能谱CT成像结合多种能谱分析技术在肾积脓和肾积水的鉴别上有着良好的预测及诊断效能。

Objective To investigate the clinical application value of various functional parameters of spectral computed tomography （CT） in the differential diagnosis of pyonephrosis and hydronephrosis. Methods A retrospective analysis was performed for 46 patients with moderate or severe renal effusion who underwent spectral CT in Department of Urology，The People’s Hospital of Nanchuan，from February 2021 to March 2023，among whom there were 18 patients with pyonephrosis and 28 patients with hydronephrosis. All patients underwent scanning in the gemstone spectral imaging （GSI） mode within the period of contrast-enhanced CT for renal effusion. The post-processing workstation and GSI browser were used to obtain the specific spectral CT parameters of the hydronephrosis area at every alternate 10 keV level of spectral CT 40~140 keV，including monochromatic spectral image，spectrum attenuation curve，quantification of inorganic compounds in urine，and effective atomic number，and the formula k=（HU40/HU100）/60 was used to calculate the slope of the spectral curve；the above parameters were compared. Then a multivariate linear regression analysis was performed for CT values on 40 keV monochromatic spectral CT imaging together with the quantification of leukocytes and calcium in pyonephrosis，and the independent samples t-test was used for the analysis of related data. The receiver operating characteristic（ROC） curve was plotted to investigate the sensitivity and specificity of each parameter in the differential diagnosis of pyonephrosis and hydronephrosis. The above parameters were analyzed to determine the diagnostic efficacy of spectral CT for pyonephrosis and hydronephrosis. Results Spectral CT showed that there were significant differences in spectral CT values between the three low-energy levels of 40-60 keV，and the lower the energy（40 keV），the greater the difference. Compared with the hydronephrosis group，the pyonephrosis group had significantly higher slope of spectral curve，effective atomic number，and contrast-to-noise ratio and significantly lower quantification of calcium，as well as a slightly higher mixed-energy CT value with no significant difference. The multivariate linear regression analysis of the degree of pyonephrosis in patients based on monochromatic spectral CT imaging and postoperative calcium ion quantification showed that the number of leukocytes （b=0.886，β=0.725，P<0.001） and urinary calcium quantification in pyonephrosis （b=-75.037，β=-0.193，P=0.043） could positively or negatively predict the CT values of the pyuria area on the 40 keV monochromatic spectral CT image，accounting for 64.8% of the prediction rate in the diagnosis of pyonephrosis. The ROC curve analysis showed that leukocyte quantification in pyuria，CT value of fluid sonolucent area on the 40 keV monochromatic spectral CT image，contrast-to-noise ratio，and relative quantification of calcium ions in pyuria had a certain diagnostic efficacy for pyonephrosis，with a relatively good predictive effect. Conclusion Spectral CT imaging combined with various energy spectrum analysis techniques has good predictive and diagnostic efficacy in the differential diagnosis of pyonephrosis and hydronephrosis.