摘要目的 探讨磁共振扩散加权成像(DW-MRI)在鉴别肾积水和肾积脓中的应用价值.方法 回顾性分析2015年3月至2017年10月我院行DW-MRI检查的50例肾结石伴可疑肾积脓患者的临床资料.男17例,女33例;年龄(49.40±10.51)岁.肾结石最大径中位值为30.30(17.38,56.01) mm,肾积液最大径中位值为46.39(34.33,56.55)mm.术前超声、CT检查均未诊断肾积脓,肾脏DW-MRI提示肾积水29例和肾积脓21例.根据经皮肾镜取石术(PCNL)中引流肾盂尿液是否为脓液,确诊肾积水和肾积脓.分析DW-MRI检查后肾积液区扩散加权(DW)图像差异特征,重建表观弥散系数(ADC)图并分析特征,比较肾积水和肾积脓患者肾积液区ADC值的差异,绘制受试者工作特征曲线(ROC),计算ADC值诊断肾积脓的临界值及其敏感性和特异性.结果 术中根据穿刺引流液性状确诊肾积水33例,肾积脓17例.术前DW-MRI诊断准确率为84.00％(42/50),敏感性为88.24％ (15/17),特异性为81.82％(27/33).在我院行CT检查的30例患者中,18例肾积水和12例肾积脓CT值分别为(7.03 ±3.26) HU和(8.67±3.52) HU,差异无统计学意义(P＞0.05).DW图中,当b值≥500 s/mm2时,肾积水信号强度明显降低,肾积脓信号强度明显增强;ADC图中,肾积水呈现高信号,肾积脓则表现为低信号.肾积脓组平均ADC值小于肾积水组[(1.53±0.58)×10-3mm2/s与(2.86 ±0.56)×10-3mm2/s,P＜0.01].绘制ROC曲线,曲线下面积为0.92(95％ CI0.80～0.98),ADC值诊断肾积脓的临界值为1.39×10-3mm2/s,此时诊断敏感性为94.12％,特异性为84.85％.结论 DW-MRI检查时,DW图中肾积脓较肾积水信号增强,而ADC图中肾积脓较肾积水信号降低,肾积脓ADC值低于肾积水,结合ADC值可有效鉴别肾积水与肾积脓.

abstractsObjective To study the effect of diffusion-weighted magnetic resonance imaging (DW-MRI) in the differential diagnosis of hydronephrosis and pyonephrosis.Methods From March 2015 to October 2017,50 patients with renal stone and highly suspected infectious hydronephrosis underwent renal DW-MRI,and clinical materials were collected and analyzed retrospectively.Seventeen male and 33 female patients were enrolled with a mean age of (49.40 ±-10.51) years.The median maximum diameter of renal stone was 30.30 (17.38,56.01) mm and hydronephrosis was 46.39 (34.33,56.55) mm.No pyonephrosis was diagnosed by preoperative ultrasound or CT,while 29 cases of hydronephrosis and 21 cases of pyonephrosis were reported by preoperative DW-MRI.Final diagnoses of hydronephrosis and pyonephrosis were made according to whether the pelvic urine drainage was purulent or not during the surgery.DW-MRI reports and characteristics of DW images were analyzed retrospectively.Apparent diffusion coefficient (ADC) was calculated and ADC map constructed,which was compared between the two groups.Receiver operating characteristic curve (ROC) was drawn to analyze the area under curve (AUC) and the optimal cutoff of ADC value,with sensitivity and specificity.Results Thirty-three patients of hydronephrosis and 17 pyonephrosis were confirmed intraoperatively.The overall accuracy of diagnosis using DW-MRI was 84.00％ (42/50),with sensitivity of 88.24％ (15/17) and specificity of 81.82％ (27/33).Among 30 patients who underwent CT scan in our hospital,mean CT value of 18 hydronephrosis was (7.03 ± 3.26)HU and that of 12 pyonephrosis was (8.67 ± 3.52) HU,with no statistical significance (P ＞ 0.05).On DW image,when b ≥ 500 s/mm2,hydronephrosis signal intensity was lowered apparently,whereas pyonephrosis signal intensity was intensified.On ADC map,hydronephrosis appeared as hyperintensity,whereas pyonephrosis appeared as hypointensity.The mean ADC value of pyonephrosis group was lower than hydronephrosis group [(1.53 ±0.58) × 10-3 mm2/s vs.(2.86 ±0.56) × 10-3 mm2/s,p ＜0.01].ROC analysis revealed that AUC =0.92 (95％ CI 0.80-0.98),and the cut-off value of ADC for pyonephrosis diagnosis was 1.39 × 10-3 mm2/s,of which the sensitivity and specificity was 94.12％ and 84.85％ respectively.Conclusions Signal of pyonephrosis was enhanced on DW image,while decreased on ADC image.The ADC value of pyonephrosis was much lower than that of hydronephrosis,with which the differential diagnosis between pyonephrosis and hydronephrosis could be made efficiently.