Other Renal Masses

Because the kidney forms from a number of embryonic parts, anomalies of shape and position are not uncommon, and can simulate renal masses. These two cases illustrate this concept.

Further Explanation:

Other Renal Masses

A common benign mass in the kidney is an angiomyolipoma. When large, they often contain macroscopic fat which can be detected based on CT density (negative HU's). But if the amount of fat is small, it may not be detectable due to volume averaging with adjacent structures. And some angiomyolipomas may contain no or very little fat. Detection of fat can be facilitated with MR imaging, where fat suppression or other special fat detection sequences can be helpful. MR can also detect microscopic fat that is not visible on CT, but since some RCCAs contain microscopic fat, this must be interpreted in conjunction with other imaging features to attempt to discriminate benign from malignant masses.

Further Explanation:

Other Renal Masses

Finally, it is important to consider the possibility of other types of tumors that can affect the kidney besides RCCA. Metastases to the kidney are rather rare, but when they occur the commonest primaries are breast, lung, GI tumors and melanoma. Systemic diseases such as lymphoma can involve the kidneys but this is also rare. These three cases are a reminder to consider other neoplastic diagnoses for renal masses, particularly if the clinical setting is not typical

Further Explanation:

This completes this self-directed learning module on Renal Imaging. Click here to go to the Knowledge Assessment questions for this material.