Small Angiomyolipomas Research Articles

Giant Angiomyolipoma Masquerading as Perinephric Abscess: A Diagnostic Conundrum

Renal angiomyolipomas are the most common benign tumours of the kidney accounting for up to 1% of all renal masses. Giant angiomyolipomas which have a size greater than 10 centimetres are rare entities with few cases reported in literature. Small angiomyolipomas are usually a symptomatic and increasing size correlates with symptomatology. These are usually incidentally detected or when symptomatic may present with an abdominal lump, flank pain or hemorrhage. Herein, we report a rare case of 45-year-old lady with giant angiomyolipoma with clinical presentation indistinguishable from perinephric abscess. The case is rare with regards to the large size of tumour and the discordant presentation unusual for an angiomyolipoma.

Small (<4 cm) Renal Mass: Differentiation of Angiomyolipoma without Visible Fat from Renal Cell Carcinoma Utilizing MR Imaging

To determine whether a combination of magnetic resonance (MR) parameters can help differentiate small angiomyolipomas (AMLs) without visible fat from renal cell carcinomas (RCCs). This HIPAA-compliant retrospective study received institutional review board approval; 69 men and 42 women (mean age, 59.7 years) with 15 AMLs without visible fat and 104 RCCs underwent MR. The development set consisted of 10 AMLs and 71 RCCs; the validation set consisted of five AMLs and 33 RCCs. T1-weighted fast spin-echo (SE), fat-suppressed T2-weighted fast SE, in- and opposed-phase gradient-echo (GRE), and fat-suppressed three-dimensional T1-weighted spoiled GRE sequences were performed before and after contrast material administration. Tumor signal intensity (SI) was measured. T1 and T2 SI ratio (ratio of tumor to renal cortex SI on T1- and T2-weighted images, respectively), SI index (SII) ([SI(in) 2 SI(opp)]/[SI(in)] × 100; SI(in) and SI(opp) are tumor SI on in- and opposed-phase images, respectively), and arterial-to-delayed enhancement ratio ([SI(art) 2 SI(pre)]/[SI(del) 2 SI(pre)]; SI(pre), SI(art), and SI(del) are tumor SI on unenhanced, arterial phase, and delayed phase three-dimensional T1-weighted spoiled GRE images, respectively) were compared. Combinations of MR parameter threshold levels were constructed from development set and validated with validation set. Sensitivity, specificity, and accuracy for differentiating between AML and RCC were calculated for combinations of MR parameter threshold levels. AML had significantly higher T1 SI ratio (P = .04), lower T2 SI ratio (P = .001), higher SII (P = .02), and higher arterial-to-delayed enhancement ratio (P < .001) than RCC. Sensitivity, specificity, and accuracy for combination of T2 SI ratio less than 0.9 and ([SII greater than 20% and T1 SI ratio greater than 1.2] or arterial-to-delayed enhancement ratio greater than 1.5) were 73% (11 of 15), 99% (103 of 104), and 96% (114 of 119), respectively, for differentiating AML from RCC. A combination of T2 SI ratio less than 0.9 and ([SII greater than 20% and T1 SI ratio greater than 1.2] or arterial-to-delayed enhancement ratio greater than 1.5) was accurate in differentiating AML from RCC.

Small (

The purpose of this study was to evaluate the ability of in-phase spoiled gradient echo combined with chemically selective fat suppression or out-of-phase spoiled gradient echo MR images to characterize small renal masses as angiomyolipomas. Eleven patients with a total of 35 small (< 1.5 cm) angiomyolipomas underwent MR examination at 1.5T. Eight patients had solitary and three patients had multiple angiomyolipomas. One of the patients with multiple angiomyolipomas had tuberous sclerosis and the number of angiomyolipomas were quantified as 20. MR examinations included in-phase spoiled gradient echo (all patients), chemically selective fat suppressed spin echo (six patients), chemically selective fat suppressed spoiled gradient echo (three patients), selective water excitation spoiled gradient echo (one patient) and out-of-phase spoiled gradient echo (seven patients). Angiomyolipomas were minimally (4 lesions) or moderately (31 lesions) high in signal intensity relative to renal cortex on in-phase spoiled gradient echo images. On out-of-phase spoiled gradient echo images, demonstration of signal void fat-water phase cancellation was present in all eight lesions in the seven patients who were imaged with this sequence. Small lesion size rendered the entire angiomyolipoma signal void in seven of these eight lesions due to phase cancellation artifact. Signal void phase cancellation of lesion border or signal void of the entire angiomyolipoma resulted in high lesion conspicuity in all lesions. Mild loss of signal intensity was observed in 7 lesions and moderate loss of signal intensity noted in 25 lesions on chemically selective fat suppressed images. On chemically selective fat-suppressed images, seven lesions were difficult to identify due to limited signal differences between medium intensity cortex and low intensity angiomyolipomas (six lesions in two patients) and moderate breathing artifact (one lesion in one patient). Characterization of small renal masses as angiomyolipomas may be reliably performed using the combination of in-phase and fat-attenuating MR sequences. Consistent image quality and high conspicuity of fat-water phase cancellation interfaces renders out-of-phase imaging a reliable fat attenuating method to demonstrate the presence of fat in small angiomyolipomas. Breath-hold fat-suppressed spoiled gradient echo is also effective; however, this technique demonstrates less signal loss in fatty lesions and is subject to problems with inhomogeneity of fat suppression.

CT pixel mapping in the diagnosis of small angiomyolipomas of the kidneys.

In six small renal angiomyolipomas (7-17 mm) the superiority of displaying the CT numbers of pixels within a lesion (pixel mapping) over the usual region of interest (ROI) measurement is described in the detection of small amounts of fat tissue. On precontrast 5 mm CT the ROI measurements were > 0 in four cases whereas pixel maps revealed pixels with values < 0 in six cases.

Small hyperechoic nodules of the renal parenchyma.

Twenty-four hyperechogenic nodules ranging from 0.5 cm to 2.5 cm in diameter were observed within the renal parenchyma in 22 patients. Eighteen patients did not complain of renal symptoms, one had microhematuria, one renal colic, and two pain in the right flank. Because of the sonographic features suggesting fat-containing masses, these lesions were considered to be small angiomyolipomas. Two of our patients underwent surgery, which confirmed this histopathologic interpretation. Twelve patients had a sonographic follow-up, which lasted from 4 to 30 months. We did not observe any change in size or shape of the lesions.