Kidney pain is caused by infection, inflammation, injury or enlargement of the kidney, or by conditions that block the flow of urine out of the kidney. Pyelonephritis (kidney infection) and kidney stones are the most common causes of kidney pain. Pyelonephritis is often accompanied by other symptoms of urinary tract infection, such as burning with urination, frequent or urgent need to urinate, bloody urine, fever, and nausea with or without vomiting.