Kidney stones (known medically as renal calculi) produce sudden excruciating, cramping pain in the low back, groin, or abdomen. This pain is referred to as renal colic and occurs when the stone is in the ureter or after the stone has left the bladder and is in the urethra. The pain comes in waves lasting 20 to 60 minutes, characteristic of colicky pain. Renal colic is associated with nausea, vomiting, fever, blood in the urine, pus in the urine, cloudy or smelly urine and painful urination. Painful urination may occur when a urinary tract infection is also present.