Loin pain hematuria syndrome is a rare condition that causes severe pain in the lower back and blood in the urine. While it is an unusual condition, there are some synonyms that can be used to describe it. These include chronic flank pain syndrome, renal colic, and nephritis. Chronic flank pain syndrome refers to any ongoing pain in the back that lasts for weeks or even months. Renal colic is used to describe the sharp, intense pain that comes on suddenly when a kidney stone is passed. And finally, nephritis is a general term used to describe inflammation of the kidneys, which can cause pain and discomfort in the back and abdomen.