肾脏乏脂肪血管平滑肌脂肪瘤与透明细胞癌的高分辨螺旋CT特征分析

Analysis of the characteristics of minimal fat renal angiomyolipoma and clear cell renal carcinoma in high resolution multi-slice spiral CT

目的比较肾乏脂肪血管平滑肌脂肪瘤（MFAML）与肾透明细胞癌（CCRCC）的高分辨螺旋CT影像特征，以提高MFAML的诊断准确率。方法回顾性分析2011年1月至2012年4月经病理证实的24例MFAML患者的临床资料，男8例，女16例。年龄19～74岁，平均43岁。同期24例CCRCC患者，男8例，女16例。年龄21～76岁，平均44岁。比较两组患者的高分辨螺旋CT影像特征，包括肿瘤的位置、密度、强化特征（强化程度、强化是否均匀、强化数值、强化方式）、边缘、钙化及肾周的改变等。采用多变量Logistic回归分析各项CT特征对两组患者的鉴别诊断价值。结果MFAML组肿瘤位于下极11例、中部7例、上极6例，CCRCC组下极9例、中部9例、上极6例；MFAML组21例和CCRCC组19例肿瘤边缘较光滑，两组比较差异均无统计学意义（P〉0．05）。两组均有21例在皮质早期明显强化，为富血供肿瘤，但CCRCC组皮质早期及皮质期的平均强化数值（175、196HU）均高于MFAML组（125、145HU），差异有统计学意义（P〈0．05）。MFAML组15例表现为均匀强化，9例为不均匀强化；CCRCC组7例为均匀强化，17例为不均匀强化，两组比较差异有统计学意义（P〈0．05）。强化方式对鉴别二者差异无统计学意义，MFAML组13例中8例为富血供肿瘤（6例为快进快出性强化，2例为持续性强化），余5例乏血供肿瘤为持续或渐进性强化；CCRCC组24例中21例为富血供肿瘤（15例为快进快出性强化，5例为持续性强化，1例为渐进性强化），余3例乏血供肿瘤为持续性强化。Logistic回归分析结果表明，平扫期高密度（OR=0．010，P=0．002）和以皮质期CT值增加129．5HU作为阈值（OR=0．057，P=0．004）是鉴别MFAML与CCRCC最有价值的特征。结论平扫期高密度及皮质期强化数值〈129．5HU是MFAML最具诊断价值的CT特征。75％富血供MFAML表现为快进快出的强化方式，其与CCRCC的鉴别存在困难。

Objective To investigate the characteristics of minimal fat renal angiomyolipoma （MFAML） and clear cell renal cell carcinoma （CCRCC） in high resolution multi-slice spiral CT （MSCT） and to improve the diagnosis accuracy for the renal tumors. Methods A retrospective analysis was performed on 24 MFAML patients （ 16 females, 8 males） with mean age of 43 （19-74） years and 24 CCRCC patients （ 16 females, 8 males） with mean age of 44 （21-76） years. All patients had undergone MSCT and proved histopathologically after surgery. The characteristics included tumor location, tumor attenuation on unenhanced CT, enhancement characteristics （degree of tumor enhancement in the early eorticomedullary phase, homogeneity of enhancement, amount of enhancement, enhancement pattern over time） , tumor margin, intratumoral calcification, and perinephric changes. The predictive value of each CT characteristic was determined by using multivariate logistic regression analysis. Results The tumor location in the kidney （upper pole： MFAML, 6 cases, CCRCC, 6 cases; middle： MFAML, 7 cases, CCRCC, 9 cases; lower pole： MFAML, 11 cases, CCRCC, 9 cases） and smooth tumor margin （MFAML, n=21; CCRCC, n=19） were not significantly different between MFAML patients and those with CCRCC, P〉0.05. Twenty-one cases of both MFAMLs and CCRCCs had the significant enhancement in the early corticomedullary phase, which were hypovaseular tumors, whereas the mean amount of tumor enhancement was greater in CCRCC than in MFAML in both the early corticomedullary and the corticomedullary phases （CCRCC： 175 HU, 196 HU; MFAML： 125 HU, 145 HU; P〈0.05. MFAML usually showed homogeneous enhancement （n = 15） rather than heterogeneous enhancement （n = 9）, whereas most CCRCC showed heterogeneous enhancement （n = 17） rather than homogeneous enhancement （ n = 7 ） , P〈 0.05 ）. Enhancement pattern was not a significant predictor. Within the 13 MFAML cases, 8 cases had sufficient blood supply （6 cases showed obvious ＂wash- in-and-wash-out＂, 2 cases were with prolonged enhancement） , 5 cases with hypovascular showed a pattern of prolonged or gradual enhancement, while 21 CCRCC cases had sufficient blood supply and 71% of them showed obvious ＂wash-in-and-wash-out＂. High tumor attenuation on unenhanced scans （MFAML： 17 patients （ 75% ） ; CCRCC ： 2 patients （ 8% ） ,P= 0.002, OR = 0.010） and threshold enhancement values of 129.5 HU in the corticomedullary phase （ MFAML ： 5 patients （ 20% ） ; CCRCC ： 20 patients （ 83% ） , P = 0.004, OR = 0.057） were valuable predictors for differentiating MFAML from CCRCC at multivariate logistic regression analysis. Conclusions MSCT is useful in differentiating MFAML from CCRCC, with high tumor attenuation on unenhanced scans and threshold enhancement values of 129.5 HU in the corticomedullary phase being the most valuable CT findings. 75% of MFAMLs with sufficient blood supply also show a pattern of ＂wash-in- and-wash-out＂, which can easily misdiagnosed as a renal cancer.