Dehydration, and certain genetic disorders are risk factors. Symptoms include pain in the flank or back, and blood in the urine. Most small stones (less than 5mm) will pass in the urine. For larger stones, treatments include lithotripsy, which is shock wave ultrasound which pulverizes the stones to smaller particles. Ureteroscopy can be used to break up the stone and pull them out through the urethra, then a stent is placed. The other treatment is percutaneous nephrolithotomy.