News from WFUMB: Contrast-enhanced ultrasound is specific for focal liver lesions
The use of echo contrast agents improves the diagnostic ability of ultrasonography to detect and differentiate liver tumors. But contrast agents have different features and there are numerous examination techniques.
Italian researchers have found that contrast-enhanced harmonic sonography with SonoVue aids in the differential diagnosis of incidentally detected focal liver abnormalities.
"It will likely save unnecessary spiral CT studies and aspiration biopsies," Dr. Luigi Solbiati said at the 10th Congress of the World Federation for Ultrasound in Medicine and Biology in Montreal on Monday.
Solbiati and colleagues from the Busto Arsizio Hospital followed 460 patients who underwent abdominal ultrasound for clinical questions unrelated to the liver and found 49 solid focal lesions. None of the patients had chronic hepatitis/cirrhosis or history of malignancy. Lesions with characteristic features of hemangioma were excluded.
Low mechanical index, continuous-mode contrast-enhanced ultrasound was performed. Final diagnosis was established by means of spiral CT, dynamic MRI, and/or fine-needle aspiration biopsy (FNAB).
In 14/14 focal nodular hyperplasias and 13/13 atypical hemangiomas, researchers found the typical enhancement pattern. Focal nodular hyperplasias exhibit early rapid enhancement of arterial vessels with a strong portal phase, while atypical hemangiomas are characterized by globular enhancement with centripetal filling.
In six patients presenting with multiple hyperechoic lesions, contrast-enhanced ultrasound showed enhancement analogous to that of the surrounding liver in all vascular phases, suggesting the diagnosis of focal fatty changes. This was subsequently confirmed with CT and FNAB.
In four patients with poorly enhancing lesions, contrast-enhanced ultrasound did not provide diagnostic findings, and FNAB was necessary to diagnose fibrotic hemangioma (one), multiple tuberculous granulomas (one), and disseminated metastases from unknown origin (two).
For the characterization of most incidentally detected and sonographically indeterminate benign lesions, contrast-enhanced ultrasound showed specificity equal to that of spiral CT, Solbiati said.
"We were confident with our diagnosis for 90% of the patients, sparing them further diagnostic workup," he said.
A multicenter study spanning seven European countries found similar results, suggesting that SonoVue-enhanced ultrasound with nonlinear imaging modes is superior to unenhanced ultrasound in characterizing focal liver tumors.
Diagnosis was made on the basis of tumor vascularity and enhancement pattern in the vascular phase and degree of contrast uptake within the lesion relative to that of normal liver in the late phase, said lead investigator Dr. Edward Leen, a radiologist at Glasgow Royal Infirmary in Scotland.
Based on the above criteria, 82 of 134 lesions were called malignant, while 52 were called benign. The sensitivity for unenhanced versus enhanced malignant lesions was 28% and 90%, respectively. The specificity for unenhanced versus enhanced benign lesions was 35% and 81%, respectively. The difference for both categories was highly significant (p<0.0001), Leen said.
