Tunnel surgery, also referred to as percutaneous nephrolithotripsy, is a form of treatment physicians use to remove kidney stones. During this procedure, a surgeon will make a small incision in your back in order to remove the stones. Once the incision is made, a narrow, hollow tube is inserted into the kidney along with a probe. The physician then removes the kidney stones through the tube. This particular kidney stone treatment is used on patients with stones less than 2cm in diameter and usually requires a short hospital stay.