肾脏肌样型血管平滑肌脂肪瘤的CT特征

Imaging features of renal myomatous angiomyolipoma on CT

背景与目的:肾脏占位性病变的检出日益增多,肾脏的肌样型血管平滑肌脂肪瘤(myomatous angiomyolipoma,m AML)与恶性病变的鉴别对诊疗有重要意义。该研究旨在探讨肾脏m AML的CT特征,以提高其诊断及鉴别的准确性。方法:回顾性分析手术病理证实的肾脏m AML10例。其中男性4例,女性6例,年龄38~64岁,平均53.2岁。分析其CT平扫、增强和临床资料,记录病灶的一般形态特征,有无可见脂肪、钙化、假包膜、瘤内囊变或出血,劈裂征是否阳性;观察其平扫及动态增强CT表现,并与邻近正常肾脏实质和同侧腰背部骨骼肌对照。结果:10例病例中,9例为单发,1例伴混合型血管平滑肌脂肪瘤。病灶位置位于左肾6例,右肾4例;5例位于肾外,5例位于肾内。所有病例均边界清楚,9例形态规则。肿瘤最大径15~80 mm,平均(43±19)mm。2例病灶含少量可见脂肪,3例含增粗的瘤内血管,2例伴囊变,所有病灶均无钙化或出血。CT平扫结果显示,7例病灶呈稍高密度,3例为等密度,5例病灶均质,3例为轻度不均,2例为不均。病灶平均CT值为(48.60±5.50)HU,显著高于邻近正常肾脏实质[(39.70±6.67)HU](P<0.05),与骨骼肌平均CT值[(48.90±2.28)HU]差异无统计学意义(P>0.05)。增强扫描结果显示,4例呈轻度强化,5例中度强化,1例明显增强;强化均匀、轻度不均匀和不均匀者分别为3例和4例、3例。持续性强化者为4例,渐进性强化者为4例,快进快出者为2例。结论:m AML在CT上主要表现为边界清楚的结节,大多不含可见脂肪,平扫呈稍高密度,均质或轻度不均,增强后呈轻度至中度强化,强化均匀或轻度不均,渐进性强化或持续性强化。对于影像表现的综合分析有利于其诊断和鉴别诊断。

Background and purpose： Since the detection of renal neoplasm is increasing, it＇s important to distinguish myomatous angiomyolipoma （mAML） from malignant tumors. This study aimed to investigate the imaging features of renal mAML on computer tomography （CT） and improve the accuracy of diagnosis and differential diagnosis. Methods： Ten patients were diagnosed with nlAML. The cases were composed of 4 men and 6 women, with a mean age of 53.2 years （range 38-64）. Among all of the cases, the percentage of spindle cell is more than 70%. Two radiologists reviewed all of the images to evaluate general characteristics, imaging features on unenhanced CT and enhanced CT. The mean attenuation on the unenhanced CT of nlAML, normal renal parenchyma and skeletal muscle was compared by the paired-sample t test. Results： Among all of the tumors, nine lesions were solitary, and the other one was accompanied with typical AML. Six lesions were at the left kidney while four lesions were at the right side. Five lesions located intracapsularly. All the lesions were well-defined, nine of them were regular. The tumor sizes ranged from 15 to 80 mm with mean （43＋19） cm. Intratumoral macroscopic fat, cystic degeneration and vessels were found in two lesions, two lesions and three lesions, respectively. Calcification or hemorrhage was not detected in any cases. On unenhanced CT, 70% cases were hyperattenuating. Eight cases were homogeneous or slightly heterogeneous. The mean attenuation of the tumor lesions on unenhanced CT was （48.60＋5.50） HU, which was higher than that of normal renal parenchyma （39.70-4-6.67） HU （P〈0.05）, and similar to that of skeletal muscle （48.9~2.28） HU （P〉0.05）.＂ After intravenous injection of contrast media, seven cases were categorized as the slightly heterogeneous or heterogeneous enhancement type. Four cases showed a weak enhancement whereas five cases were with a moderate enhancement. The gradual, prolonged and early washout enhancement patterns were observed in 40%, 40%, and 20% of the cases, respectively. Conclusion： The radiological appearance of mAML had a tendency to be hyperattenuating on unenhanced CT images without macroscopic fat; it could be homogeneous or slightly heterogeneous on unenhanced scans. After the injection of contrast agent, mAML tended to have a weak or moderate, lightly heterogeneous to heterogeneous enhancement, and it could demonstrate gradual and prolonged enhancement patterns.