VIENNA - Thanks to its sensitivity for slight blood flow in tumors, contrast-enhanced ultrasound (CEUS) can be very useful for characterizing hypovascular masses that were indeterminate on contrast-enhanced CT or MRI, Italian researchers reported on Thursday at ECR 2016.
A team led by Dr. Edoardo Raimondi of the University of Ferrara in Italy found that CEUS showed contrast-enhancement wash-in in two-thirds of indeterminate small renal masses on CT or MRI. CEUS facilitates more accurate evaluation of tumor perfusion and vascular enhancement patterns and should be considered in future diagnostic algorithms for managing solid renal masses, according to the researchers.
"It can be a problem-solving tool in the assessment of those indeterminate renal findings," Raimondi said. He presented the study results during a scientific session on Thursday morning.
Incidental findings
Renal masses are increasingly detected as incidental findings on ultrasound, CT, and MRI exams, and they are typically evaluated by multidetector contrast-enhanced CT or contrast-enhanced MRI. Small renal masses are less than 3 cm in their largest dimension and are classified as either solid or complex cystic (class 3 or 4 under the Bosniak classification system for renal cystic masses), Raimondi said.
"[It's also important] to remember that almost 50% of small renal masses are [renal cell carcinomas]," he said.
An indeterminate renal mass is a lesion that can't be confidently diagnosed as benign or malignant when it's found, Raimondi said. These lesions can have enhancement on CT between 20 HU and 70 HU, have intermediate signal intensity on MRI, and be isoechoic or hypoechoic on ultrasound.
"So the principal aspect that we have to look at is the enhancement of the lesion," Raimondi said.
Contrast-enhancement wash-in is a typical sign for a malignant solid renal mass, but some benign lesions can also show contrast wash-in, such as oncocytomas. In addition, 17% to 20% of renal tumors are hypovascular on cross-sectional imaging. Furthermore, contrast enhancement of 10 HU to 30 HU -- a level considered to be pseudoenhancement -- can't be confidently suggestive of malignancy, Raimondi said.
Diagnostic value of CEUS
To address this problem, the researchers set out to explore the role and diagnostic value of CEUS for these masses. The study, which was performed from January 2012 to July 2015, included 39 patients (25 men, 14 women; age range, 40-81) who had hypovascular small renal masses with an inconclusive contrast enhancement pattern on CT or MRI. Of these, 32 patients had masses identified on contrast-enhanced CT and seven had masses found on contrast-enhanced MRI.
All 39 patients received CEUS within a week of their CT or MR study. The real-time CEUS pattern of all small renal masses was evaluated to define their diagnostic therapeutic management, Raimondi said.
Of the 39 patients, 13 had no pathological levels of contrast-enhancement, indicating complex cysts. These were classified as Bosniak 2-2F and the patients did not undergo surgery. The other 26, however, had wash-in contrast enhancement. Four of the 26 were deemed to be ineligible for surgery and are currently under follow-up with CEUS or MRI, he said.
Based on the imaging findings and the clinical suspicion for malignancy, the remaining 22 patients received nephron-sparing surgery. Seventeen of the masses were malignant; there were 10 cases of papillary renal cell carcinoma, six cases of clear cell carcinoma, and one chromophobe. The five benign masses consisted of three cases of minimal-fat angiomyolipoma and two cases of oncocytoma.
"CEUS is a useful tool in evaluating real-time enhancement in small renal masses because it's very sensitive for slight tumor blood flow," Raimondi concluded.
![Examples of ultrasound findings and techniques. (A) Images in a 39-year-old male patient with a mass in the left thigh. The mass is heterogeneous on the B-mode US image (compared with the patient in D) and showed increased microvascularity (superb microvascular imaging [SMI]) and shear-wave elastography (SWE) values. Undifferentiated pleomorphic sarcoma was diagnosed at biopsy (with pleomorphic rhabdomyosarcoma in surgical specimen). (B) Images in an 18-year-old male patient with a mass in the left leg. The mass is hypoechoic on the B-mode image, with no other findings suggestive of malignancy. The lesion is in contact with the cortex of the tibia, which is slightly irregular. CT revealed a doubtful anteromedial tibial erosion. The microvascular study demonstrated high vascularization, suggestive of malignancy. Periosteal Ewing sarcoma was diagnosed with both histologic and immunohistochemical confirmation. (C) Images in a 69-year-old female patient with a lump growing on the outside of the left leg. Multiple SWE examinations were performed (please note the high values obtained in the measurements, whereas the color map highlights the stiffness relative to adjacent tissues). SMI showed areas of increased vascularization to target for sampling. Undifferentiated spindle cell sarcoma was diagnosed at biopsy, with residual leiomyosarcoma in the surgical specimen after neoadjuvant therapy. (D) Images in a 56-year-old female patient with a mass in the right thigh. The mass is heterogeneous at both B-mode ultrasound (similar to patient A) and MRI (coronal T2-weighted spectral attenuated inversion recovery [SPAIR]; T1-weighted pre-contrast and postcontrast imaging), which even shows uptake after the administration of paramagnetic contrast material, which is traditionally suggestive of malignancy. Low values at SMI and elastography are suggestive of benignity. Spindle cell lipoma was diagnosed at biopsy, with atypical spindle cell lipomatous tumor in the surgical specimen.](https://img.auntminnie.com/mindful/smg/workspaces/default/uploads/2026/08/images-radiol250278fig2.APCFLSvX6p.jpg?auto=format%2Ccompress&dpr=2&fit=crop&h=167&q=70&w=250)
