Three Kidneys
A 38-year-old Brazilian man started experiencing lower-back pain but thought it was nothing. Unfortunately, his pain became more and more severe, so he decided to go to the doctor and get himself checked. Doctors performed a CT scan on him and discovered something extremely rare: he had three kidneys.
Luckily, the culprit wasn't his kidneys but a herniated disk. Still, doctors were fascinated by this discovery and performed more studies on him. His kidneys all function normally, and there are only 100 documented cases of this around the world.