A kidney mass is a growth that arises from inside the kidney, according to Washington University School of Medicine in St. Louis. Most kidney masses are found when a patient is undergoing evaluation for something else and receives an ultrasound or CT scan.
Cysts are the most common kidney masses, explains WUSM St. Louis. These fluid-filled sacs appear in half of people older than 50. Cysts do not generally cause medical problems or comprise any significant risks. Radiologists can easily identify most cysts, most of which do not require any intervention. In some cases, no further observation is necessary. Other cysts, however, are complex and provide more of a challenge. People who have complex cysts receive follow-up monitoring through CT scans or MRI, which look for changes and growth in the cyst.
Solid kidney masses are more worrisome than the liquid-filled cysts, notes WUSM St. Louis. About four out of five solid kidney masses turn out to be cancerous. To err on the side of caution, the noncancerous masses are often treated as though they cancerous. Sometimes a doctor orders a biopsy of the mass to provide more information, but biopsies are not always reliable as far as determining the malignancy of a mass. In most cases, the doctor uses such treatments as freezing the mass, or laparoscopic partial nephrectomy. In other cases, the surgeon may choose an open partial nephrectomy, if the situation is too complex for laparoscopic handling, notes WUSM St. Louis.