CT diagnosis of renal angiomyolipoma: the importance of detecting small amounts of fat

Abstract

Materials and MethodsSix patients were reviewed who had small angiomyolipomas (1 .2-4.0 cm) that contained tiny amounts of fat. A GE 8800 scanner was used in two patients and a GE 9800 in five; in one patient, one scan was obtained with each machine. Standard 1 0-mm-thick sections were used in all cases; four patients also were studied with 5-mm sections.In all patients, scans were obtained with IV contrast material; three patients had unenhanced scans as well. In total, 45 g of iodine were administered by the rapid bolus-infusion technique. Fatty tissue was considered to be present within a tumor if a region-of-interest value of -10 H or lower was found within the tumor. Region-of-interest measurements were used that included at least a total of three adjacent pixels. In three cases, the region-of-interest measurement included nine pixels or more. CT scanners were calibrated daily with a phantom.

Fat detection in granular-cell renal cell carcinoma using chemical-shift gradient-echo MR imaging: another renal tumor that contains fat

“…mors. The fat in these tumors is macroscopic and exhibits negative attenuation value on CT or as bright signal relative to subcutaneous or retroperitoneal fat tissue on T1-weighted MR images [2,3]. RCC, the most common malignant tumors arising from the kidney, rarely show this macroscopic fat on radiologic examinations, although rare exceptional cases have been reported sporadically [5][6][7][8][9].…”

“…Thus, this most common renal malignant tumor was added to a list of differential diagnoses of renal tumors that contain radiologically detectable fat in a broad sense of the word. Angiomyolipoma, classically called renal tumors for which radiologic detection of fat is pathognomonic, usually have macroscopic fat that creates negative attenuation value on computed tomography (CT) or bright signal on conventional T1-weighted MR images [2,3]; conversely, cytoplasmic fat in clear-cell RCC is microscopic and is detectable only by chemical-shift gradient-echo MR imaging and not by CT or conventional T1-weighted MR images [1,4].…”

The small renal mass: detection, characterization, and management

“…With CT or MR imaging, fat is detectable in nearly all AMLs ( Fig. 2) [14,15], thereby confirming the diagnosis. If fat is not detectable with an adequate CT or MR imaging examination, a solid mass should be presumed to be an RCC.…”

“…If the imaging features are typical for a simple cyst, i.e., water density content without enhancement and smooth thin margins, a simple cyst can be diagnosed without further imaging evaluation. In addition, fat detected within a solid renal mass indicates a diagnosis of AML [15], and no further imaging is necessary for characterization of the mass unless the imaging findings suggest that the fat is not intrinsic to the tumor but is perirenal fat that has been encompassed by an aggressive renal malignancy. Unfortunately, some small renal masses lack definitive CT features.…”

Nieren-Spiral-CT

“…Der Tumor ist oft mit einer tuberösen Sklerose (Phakomatose) vergesellschaftet. Charakteristisch ist der hohe Anteil fetthaltiger Strukturen mit HE-Werten unter -10 [2]. Sind die Fettanteile dagegen gering, kann es nach KM-Gabe zu einem "Über-deckungseffekt" kommen, der die charakteristischen Fettstrukturen nur schwer nachweisen läßt.…”