Kidney stones form in the kidney . If they stay in the kidney , they do not typically cause pain. When they travel out of the body through the tubes of the urinary tract (including the ureters, which connect the kidney to the bladder, or the urethra, which leads outside the body), their movement may cause:

•    No symptoms, if the stone is small enough.

•    Sudden, severe pain that gets worse in waves. Stones may cause intense pain in the back, side, abdomen, groin, or genitals. People who have had a kidney stone often describe the pain as "the worst pain I've ever had."

•    Feeling sick to the stomach (nausea) and vomiting.

•    Blood in the urine (hematuria ), which can occur either with stones that stay in the kidney or with those that travel through the ureters.

•    Frequent and painful urination, which may occur when the stone is in the ureter or after the stone has left the bladder and is in the urethra. Painful urination may occur when a urinary tract infection is also present.