MCQ – 93372

Correct Answer » C Explanation

On the CT image, the arrows point to renal cortical lesions that contain fat-density areas (very low attenuation, appearing dark).
Macroscopic fat within a renal mass is the key imaging hallmark of angiomyolipoma (AML).
The presentation with vague abdominal pain in a middle-aged patient is also typical, as AMLs are often incidental but can cause pain if they enlarge or bleed.

Renal angiomyolipoma is a benign tumor that consists of a mixture of blood vessels, smooth muscle cells, and fat cells. It is typically seen as a well-defined mass with fat density on a CT scan. Angiomyolipomas are often associated with tuberous sclerosis and can occasionally cause symptoms such as abdominal pain or hematuria.

Key Points for Identifying Renal Angiomyolipoma on CT

Characteristic Features: Renal angiomyolipomas are benign renal tumors that contain a mixture of blood vessels, smooth muscle, and fat. The presence of fat density (appearing dark on CT) within the mass is a hallmark of angiomyolipoma.

Bilateral Presentation: Although angiomyolipomas are often unilateral, they can sometimes appear in both kidneys, especially in cases associated with tuberous sclerosis.

Mixed Density: The CT image demonstrates mixed density within the lesions, consistent with fat components and soft tissue, which are common in angiomyolipomas.

Why Other Options Are Less Likely

Renal Cell Carcinoma (RCC): RCC typically appears as a solid, enhancing mass with irregular borders. It usually does not contain fat, so it would not show the mixed densities characteristic of angiomyolipomas.

Renal Oncocytoma: Oncocytomas are solid masses and generally do not contain fat. They present as homogeneous masses rather than mixed-density lesions.

Renal Cyst: Simple renal cysts appear as homogeneously low-density (fluid-filled) structures without mixed density or fat components. They do not show the mixed densities seen in this image.