I had a CT scan done last week that revealed the following: KIDNEYS: 6 mm hypodense lesion in the right lower pole, too small to be characterized but likely a cyst. No stones or hydronephrosis. Everything else on the CT scan came back as normal and the conclusion was the following: IMPRESSION: 1. No findings to explain symptoms of abdominal pain, nausea and vomiting 2. 6 mm right renal cyst What makes the doctors so confident that this lesion is a cyst and not a tumour? This was performed at Brigham and Women s Hospital in Boston.