It is possible that some kidney stones and ureteral stones up to 5 millimeters can be expelled naturally. Kidney stones, ureteral stones have to pass through the narrowing part of the ureter to be drained into the bladder and out of the body through the urethra. The lumen of the ureter is about 3 to 4 millimeters After antispasmodic drugs the lumen expands by about 5 millimeters, so it is possible that kidney stones and ureteral stones under 5 millimeters can be expelled naturally. Kidney stones are more difficult to be expelled naturally if the stone is in a narrow area or if the stone is larger than 5 millimeters. If the stone cannot be expelled by itself, it can be treated by extracorporeal shock wave lithotripsy, or transurethral laser lithotripsy, and percutaneous nephrolithotripsy. Stones should be examined in a timely manner and treated in accordance with medical advice.