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Kidney: Angiomyolipoma: Aml Imaging Pearls - Learning Modules | CT Scanning | CT Imaging | CT Scan Protocols - CTisus
Imaging Pearls ❯ Kidney ❯ Angiomyolipoma: AML

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  • “Patients with lymphangioleiomyomatosis (LAM) have a frequency of angiomyolipoma (AML) that varies from 20% to 54% depend- 
ing on the method of patient or case collec- tion, imaging modality used, diagnostic criteria, and statistics of sampling variation. This frequency of AML is much higher than the reported frequency of 1–3% in the general population.”


    Active Surveillance of Nonfatty Renal Masses in Patients With Lymphangioleiomyomatosis: Use of CT Features and Patterns of Growth to Differentiate Angiomyolipoma From Renal Cancer 
Nilo A. Avila et al.
AJR 2017; 209:611–619
  • “AMLs with no visible fat that are hyperattenuating relative to the normal renal parenchyma on unenhanced CT have been called “AML with minimal fat,” and AMLs that are hypoattenuating relative to the normal renal parenchyma but with attenuation values not in the range of fatty tissue on unenhanced CT have been termed “AML with diffusely scattered fat”. In this article, we use the term “nonfatty renal mass” to denote any renal mass with no visible fat on CT and the term “nonfatty AML” to denote an AML with no visible fat on CT.”


    Active Surveillance of Nonfatty Renal Masses in Patients With Lymphangioleiomyomatosis: Use of CT Features and Patterns of Growth to Differentiate Angiomyolipoma From Renal Cancer 
Nilo A. Avila et al.
AJR 2017; 209:611–619
  • “Renal AML can be classified according to amount of fat as fat rich, fat poor, or fat invisible. To detect fat, one needs to thoroughly evaluate the entire AML by controlling the size and shape of the ROI. Fat-invisible AML should be biopsied, and fat-poor AML requires further investigation to determine whether biopsy is necessary to differentiate it from renal cell carcinoma. If differentiation between AML and renal cell carcinoma is not clear with CT and MRI, percutaneous biopsy may be performed.”


    Renal Angiomyolipoma: Radiologic Classification and Imaging Features According to the Amount of Fat 
Byung Kwan Park 
AJR 2017; 209:826–835
  • “Angiomyolipoma (AML) is the most common benign solid renal tumor. Most AMLs contain fat that is clearly visible on CT and MR images, so these tumors can be easily diagnosed without biopsy or surgery. Approximately 5% of renal AMLs, however, have too little fat to be identified in a CT or MRI examination. Preoperatively, these AMLs are difficult to differentiate from renal cell carcinoma (RCC) with radiologic examinations, and they frequently are diagnosed after surgery.”

    
Renal Angiomyolipoma: Radiologic Classification and Imaging Features According to the Amount of Fat 
Byung Kwan Park 
AJR 2017; 209:826–835


  • Renal Angiomyolipoma: Radiologic Classification and Imaging Features According to the Amount of Fat 
Byung Kwan Park 
AJR 2017; 209:826–835
  • 
“Unenhanced CT clearly depicts a hypoattenuating area (≤ –10 HU) suggesting fat in fat-rich AML. There- fore, detecting fat is not a problem in most fat-rich AMLs. However, some fat-rich AMLs have very small foci of fat measuring less than –10 HU, so these hypoattenuating areas may not be recognized at preoperative CT. Therefore, meticulous care should be taken not to miss a small focus of fat. Thin (< 5 mm) slice thickness (1.5–3 mm) should be used because thick (≥ 5 mm) slice thickness may not depict fat attenuation.”


    Renal Angiomyolipoma: Radiologic Classification and Imaging Features According to the Amount of Fat 
Byung Kwan Park 
AJR 2017; 209:826–835
  • 
“Unenhanced CT cannot show fat attenuation in fat-invisible AMLs . These lesions appear homogeneously hyperattenuating because they have too little fat . The attenuation of fat-invisible AML is higher than that of fat-poor AML because the amount of fat in the former is lower than that in the latter. For this reason, the attenuation values of fat-invisible AML are fairly constant compared with those of fat- poor AML wherever an ROI is placed.”

    
Renal Angiomyolipoma: Radiologic Classification and Imaging Features According to the Amount of Fat 
Byung Kwan Park 
AJR 2017; 209:826–835
  • “Contrast-enhanced CT is not necessary for diagnosing fat-rich AML but should be performed when there is potential for tumor bleeding. Frequently, large fat-rich AMLs contain a lot of tortuous or dilated vessels, which are susceptible to bleeding. Contrast-enhanced CT is essential to identify these abnormal vessels before embolization.”


    Renal Angiomyolipoma: Radiologic Classification and Imaging Features According to the Amount of Fat 
Byung Kwan Park 
AJR 2017; 209:826–835
  • 
“Contrast-enhanced CT frequently shows heterogeneous enhancement within fat-poor AMLs because a small amount of fat is localized or scattered. Therefore, this type of AML may be misdiagnosed as clear cell RCC, which is heterogeneously enhancing on contrast-enhanced CT images. Still, it is unclear that fat-poor AML requires MRI or percutaneous biopsy. By definition, MRI is necessary to identify fat-poor AML. However, clear cell RCCs may have similar MRI features to those of these AML.”


    Renal Angiomyolipoma: Radiologic Classification and Imaging Features According to the Amount of Fat 
Byung Kwan Park 
AJR 2017; 209:826–835
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