Q: I recently found that I have a 3mm non-obstructing calculus in the upper to mid pole of the left kidney as well as a 7mm cyst in the mid pole of the left kidney. I have had pain, which I am assuming is from the stone, for over two months. I drink a lot of water and was told by an urologist that the stone is too small to do anything with. Also, he said at this time the “cyst” is too small to tell if it is benign or a tumor, and they have to watch it until it gets bigger. He also said this “cyst” should not cause any pain. I am wondering if what he is saying is correct or should I get a second opinion? I had two stones six years ago which I successfully passed and wonder why this one is different. The last stones only took a couple of days to pass. I am also extremely anemic.

A: Small stones, generally less than 5 mm, pass on their own most commonly and I would recommend a low salt diet with plenty of water. Most of the time they will pass. A 7 mm cyst is at the minimum level of detection for either ultrasound or CT scanning and can be very difficult to see and evaluate. In order to be sure that a cyst is truly a benign fluid filled cyst, it is best to be at least 10 mm or 1 cm in diameter. Even small tumors that are less than 1 cm are most likely benign.  As this grows with time, one will be able to tell benign cyst from solid tumor. Tumors that are growing, solid and are nearing 4 cm in size should be more carefully evaluated and may need to be removed. Cancers rarely spread until they are of larger size, generally as they approach 4 cm. Hence, careful follow up with repeat ultrasound or CT scan in 6 to 12 months is an appropriate approach to evaluation of these lesions. You may need to undergo a stone evaluation to diagnose the cause of your recurrent stone disease and this will lead to appropriate preventative therapy.

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