Application of diffusion-weighted magnetic resonance imaging in the differential diagnosis of hydronephrosis and pyonephrosis / 中华泌尿外科杂志

ABSTRACT

Objective 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.