Conventional ultrasound findings
Uroradiology & genital male imaging
Case TypeClinical Cases
Authors
Maria Alexandratou,Vasileios Rafailidis, Panos Prassopoulos
Patient55 years, female
A 55-year-old female patient presented with lower extremity deep vein thrombosis. During her imaging work-up an incidental lesion was detected in the right kidney. Past medical history was unremarkable.
A well-circumscribed homogeneously hyperechoic lesion was detected on B-mode US, showing only mild vascularity on colour and power Doppler US (Fig. 1A, B). A contrast-enhanced ultrasound (CEUS) study was performed to evaluate the enhancement pattern of the lesion. The lesion showed homogeneous enhancement which was slower and lower than the adjacent renal parenchyma and no wash-out (Fig. 2). The diagnosis was further confirmed with CT, where the lesion was partially of macroscopic fat density, also containing parts of soft tissue density, but without calcifications (Fig. 3). Of note, CEUS outperformed CT in visualizing enhancement of the macroscopic fat component, the earlier enhancement of soft tissue parts in real-time, while arterial phase CT revealed aneurysmal dilatation of intratumoural vascularity.
Renal angiomyolipoma (AML) is a benign renal neoplasm consisting of varying amounts of vessels, fat and smooth muscle tissue [1]. AML may be sporadic or associated with tuberous sclerosis, is usually unilateral, shows a female predilection and a slow growth rate. Syndromic tumours tend to grow faster and be multifocal. Although typically asymptomatic, AMLs larger than 4 cm may present with spontaneous rupture and haemorrhage, associated to tumour vascularity [2]. The elastin-poor intratumoural vessel walls render them prone to aneurysm formation and thus rupture [2]. The risk for rupture, malignant sarcomatous transformation and the reported potential of synchronous occurrence of oncocytoma or renal cell carcinoma (RCC) justify closer surveillance instead of surgical removal [2-4].
Imaging features of AML stem from the combination of various proportions of fat, smooth muscle tissue and vascular structures. AMLs containing macroscopic fat appear hyperechoic and circumscribed on greyscale ultrasound [5]. Nevertheless, lipid-poor AMLs appear isoechoic, due to the paucity of macroscopic fat and thus need to be differentiated from RCC for treatment decision making [6]. Small RCC can be particularly problematic as they appear homogeneous and can mimic AML.[5]. Lipid-poor AML represents a diagnostic conundrum not only for US but also for other modalities. The use of contrast-enhanced imaging provides a much more accurate characterization of such indeterminate renal lesions [6,7]. Contrast-enhanced ultrasound (CEUS) provides information regarding the enhancement intensity and homogeneity, the wash in and wash out pattern and perilesional rim-like enhancement of a renal mass [8]. It involves no ionizing radiation, has rare and mild adverse reactions and is a real-time study of the tumour vascularity thanks to the blood-pool contrast agent employed [8]. On CEUS AML presents as homogeneously hypo-enhancing or iso-enhancing with a delayed enhancement pattern compared to the adjacent renal parenchyma [8]. Thanks to the technique’s optimal contrast resolution, the vascularity is accurately visualized even on the macroscopic fat component of the tumour, which shows only minimal enhancement on CT. Time-intensity-curve analysis can be used to quantify the enhancement pattern of these tumours and suggest the diagnosis of a hyper- or hypo-vascular type of lesion [9,10]. CEUS is currently recommended for the characterization of the indeterminate renal lesion according to EFSUMB and ACR appropriateness criteria [11,12]. Limitations of CEUS compared to CT and MR is the limited depth in obese patients, bowel gas interposition, the narrow field of view and the operator-dependent nature [8].
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URL: | https://www.eurorad.org/case/17575 |
DOI: | 10.35100/eurorad/case.17575 |
ISSN: | 1563-4086 |
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