Contrast-enhanced sonography of adrenal masses: differentiation of adenomas and nonadenomatous lesions.

OBJECTIVE: The aim of this proof-of-principle study was to evaluate contrast-enhanced sonography in the characterization of adrenal masses.

SUBJECTS AND METHODS: Thirty-five consecutively registered patients with newly detected adrenal masses underwent hormonal evaluation and duplex and Doppler sonography followed by contrast-enhanced sonography and CT or MRI. The dynamics of contrast enhancement were analyzed with time-intensity curves. CT and MRI were used as the reference methods for the diagnosis of adenoma and myelolipoma. Metastasis was diagnosed with fine-needle biopsy, and all other adrenal masses were diagnosed at adrenalectomy. Fisher's exact test was used to evaluate the criteria for diagnosis of malignant adrenal masses.

RESULTS: Size greater than 4 cm and hypervascularization were found significantly more often in malignant than in benign lesions (71% vs 21% for size; 57% vs 7% for hypervascularization). At contrast-enhanced sonography, early arterial or arterial contrast enhancement and rapid washout were seen in all patients with primary or secondary malignant lesions of the adrenal gland and in only 22% of patients with benign adrenal masses (p < 0.05). All primary malignant lesions were confirmed at histologic examination. In 32 of 35 patients (91%), findings at CT or MRI were congruent with those at contrast-enhanced sonography in regard to characterization of adenoma versus nonadenomatous lesion (p < 0.001). In two of the 35 cases, however, all imaging methods favored the diagnosis of nonadenomatous lesion, but the histologic result after adrenalectomy was adrenal adenoma. The sensitivity and specificity of contrast-enhanced sonography in the diagnosis of malignant adrenal mass were 100% and 82%.

CONCLUSION: Contrast-enhanced sonography can be used to differentiate adenomas and nonadenomatous lesions with a sensitivity comparable with that of CT and MRI and may be a cost-effective method for preselection of patients with adrenal masses.