Harvard Women's Health Watch

By the way, doctor: Should I be worried about a kidney cyst?

Q. Recently, I had a pelvic ultrasound to evaluate uterine fibroids. During the procedure, the radiologist found a cyst in one of my kidneys. Should I be concerned about kidney cancer?

A. Kidney (or renal) cysts are small, fluid-filled sacs in the kidneys; they're usually harmless and rarely cause symptoms. Such cysts are quite common, and many people have them without knowing it. The likelihood of having one or more cysts increases with age — from 5% of people in their 30s to more than 36% of those in their 70s. In most cases, cysts are discovered incidentally during an ultrasound, CT scan, or MRI scan for some other health reason.

When a kidney cyst is detected, the first step is to determine whether it's "simple" or "complex." Simple kidney cysts are thin, round sacs filled with clear fluid, and they're not cancerous. Complex cysts may have thick walls, several lobes, calcium flecks, or solid components. They're usually benign, but they do need to be evaluated to make sure they don't contain cancer. The first step is to get a better look using an MRI or CT scan. A urologist will examine the scan and recommend watchful waiting, biopsy, or removal.

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