成人后肾腺瘤的MRI特征

MRI features of adult metanephric adenoma

目的 探讨后肾腺瘤的MRI特征.方法 回顾性分析经手术及术后病理确诊为后肾腺瘤,术前2周内进行过MRI常规、DWI及动态增强扫描的6例患者的资料.观察病变的MRI特征,测量平扫及皮质期、髓质期、延迟期病变、对侧正常肾皮质和肾髓质的信号特征,并计算强化幅度,测量病灶ADC值.采用配对样本t检验比较肾皮质、肾髓质与病灶间信号强度及强化幅度的差异.结果 病变均为单发实性肿块,右肾4例,左肾2例.病变最大径（21～79）mm,平均（41±20）mm.5例呈类圆形及卵圆形,1例为不规则形.5例T2WI信号强度比肾实质略低,1例略高于肾实质.DWI呈明显高信号,ADC图显示低信号,病灶ADC值为（0.759±0.211）×10^-3mm^2/s.出血2例,坏死1例,2例可见包膜,6例均无瘢痕、脂质及脂肪,未见肿大淋巴结.平扫病灶信号略低于正常肾皮质、高于肾髓质,差异无统计学意义（P〉0.05）.动态增强扫描病变持续轻中度强化.皮质期、髓质期、延迟期,病灶信号强度均低于肾皮质,差异有统计学意义（P〈0.05）;皮质期、髓质期,病灶信号强度和肾髓质差异无统计学意义（P〉0.05）,延迟期病灶信号强度低于肾髓质,差异有统计学意义（P〈0.05）.除皮质期病变与肾髓质的强化幅度差异无统计学意义（P〉0.05）外,其他期相肾皮质、髓质和病灶比较,强化幅度差异均有统计学意义（P〈0.05）.结论 后肾腺瘤的MRI表现具有一定特征性,以实性病变为主,病灶信号强度低于肾皮质,以缓慢持续强化为特征,DWI上表现为高信号,ADC低.

Objective To investigate MRI features of metanephric adenoma（MA）. Methods The retrospective analysis was performed on 6 adult patients that were scanned by regular, DWI and dynamic-enhancement MRI two weeks before surgery and diagnosed with MA pathologically after surgery. MRI features of lesions were observed. The signal intensities of lesions and contralateral normal renal cortex and medulla were respectively measured in plain scan, cortex, parenchyma and delayed phase. The enhancement magnitudes were calculated and the ADC values of lesions were measured. The differences of the signal intensity and enhancement magnitude were assessed by paired-sample t test among renal cotex, medulla and lesions. Results All lesions in MA were single and solid masses. Four cases occurred in the right kidney and two cases in the left kidney. The maximum diameters of the lesions ranged from 21 to 79 mm and the mean value was（41 ± 20）mm. Five cases were round or oval, while one case was irregular. The signal intensity in five cases was slightly lower in T2WI than the renal parenchyma, while one case was slightly higher than the renal parenchyma. The hyperintentsity of DWI and hypointensity of ADC were seen in all cases. The mean ADC value was（0.759 ± 0.211）×10^-3mm^2/s. Hemorrhage were seen in two cases. Necrosis was present in one case and the capsules were seen in two cases. No scar, fat and swollen lymph nodes was seen in all cases . There was no statistical significance of the signal intensity between lesions measure in the plain scan and normal renal parenchyma（P〉0.05）. After adminstrating contrast materials, all lesions shown persistently mild to moderate enhancement . The siganl intensities of lesions measured in three phases after enhancement were signifcantly lower than those of the renal cortex（P〈0.05）. No significant differences of the signal intensity measured in cortex and medulla phase between lesions and normal renal medulla was present（P〉0.05）. But the signal intensities of leisons in delayed phases were significantly lower than thoseof renal medulla（P〈0.05）. Except from the difference of enhanced magnitude in cortex phase between lesions and normal medulla, significant differences were present between leisons and normal renal parenchyma（P〈0.05）. Conclusion MRI manifestations of MA show certain distinction, including, dominantly solid lesions, relatively lower signal intensity of lesions than that of renal cortex, slowly persistent enhancement, high signal on DWI and low signal on ADC.