Sonography in Benign and Malignant Renal Masses

Management of incidental renal masses: Time to consider contrast-enhanced ultrasonography

Proliferation of imaging studies for different clinical purposes and continuous improvement of imaging technology have led to an increasing number of incidental findings of renal masses. It is estimated that over 50% of patients older than 50 years have at least one renal mass. The majority of incidental renal masses are simple cysts that can be easily diagnosed by conventional ultrasonography. However, some incidental renal masses are not simple cysts, and differentiation between benign and malignant entities requires further imaging modalities. In the past, multiphase contrast-enhanced computed tomography and magnetic resonance imaging were considered the primary imaging modalities used to characterize and stage complex cystic and solid renal lesions. Currently, contrast-enhanced ultrasonography represents a novel alternative to contrast-enhanced computed tomography and magnetic resonance imaging. Contrast-enhanced ultrasonography employs microbubble contrast agents that allow the study of different enhancement phases of the kidney without risk of nephrotoxicity and radiation exposure. The diagnostic accuracy of contrast-enhanced ultrasonography in the characterization of complex renal cysts is comparable to that of computed tomography and magnetic resonance imaging, and several studies have demonstrated its reliability also in identifying solid lesions such as pseudotumors, typical angiomyolipomas, and clear cell renal carcinomas. Considering the high incidence of incidental renal masses and the need for rapid and reliable diagnosis, contrast-enhanced ultrasonography could be proposed as the first step in the diagnostic work-up of renal masses because of its safety and cost effectiveness. In this paper, we propose a diagnostic algorithm for the characterization of cystic and solid renal masses.

Usefulness of contrast-enhanced ultrasonography in the diagnosis of renal pseudotumors

BACKGROUND

Within the term "pseudotumors" are grouped some renal anatomic variations that may simulate a focal renal lesion at ultrasonography. Our purpose was to assess the accuracy of contrast-enhanced ultrasonography (CEUS) using a second-generation contrast agent in the diagnosis of renal pseudotumors.

METHODS

We retrospectively retrieved CEUS examinations performed in 24 patients for characterization of suspected renal pseudotumor, in which conventional and power Doppler US study had been unable to confidently exclude a neoplasm. The considered criterion to define the diagnosis of renal pseudotumor was the demonstration of the same perfusion and reperfusion after microbubble breakage in both pseudotumor and surrounding parenchyma during early and late corticomedullary phase. In all patients, multiphase CT or dynamic MRI was available, representing a standard of reference for this study. In cases of CT or MRI diagnosis of renal lesion, final diagnoses were obtained with percutaneous renal biopsy or with surgery.

RESULTS

Contrast-enhanced ultrasonography diagnosis was concordant with MR or CT images in all cases.

CONCLUSION

In our experience CEUS shows complete concordance with CT and MRI in the characterization of all 24 pseudotumors considered dubious at conventional and power Doppler US. The appropriate use of CEUS can reduce the need for contrast-enhanced CT or dynamic MRI in this item.

Renal pseudotumors

OBJECTIVE

Renal cell carcinoma is the most common malignant tumor to involve the kidneys; however, a number of other entities--called renal pseudotumors--may mimic renal neoplasms on imaging. This article presents the imaging features and pathologic correlation of some of the common and uncommon renal pseudomasses.

CONCLUSION

Many renal lesions look similar to renal cell carcinoma on radiologic imaging. The imaging features of renal pseudotumors presented in this article will help radiologists to identify them and to triage these patients for appropriate management.