Kidney stones form when crystals separate from urine and stick together inside the kidney or urinary tract. They can cause severe pain and blood in the urine. Risk factors include dehydration, family history, and medical conditions. Symptoms include intense pain in the back or side and blood in the urine. Diagnosis is usually done with a CT scan. Small stones often pass on their own but larger ones may require lithotripsy or surgery to break up the stones. Drinking plenty of water can help prevent kidney stones from forming.