The sigmoid arteries provide blood to the lower part of the colon. The specific parts of the colon they supply are the iliac colon, the pelvic colon, and the descending colon. There are always two and sometimes three or four of these arteries located in the colon. The arteries route indirectly downward, as well as on a leftward path behind the peritoneum, which is the lining of serous membrane that goes along the walls of the coelom, or the abdominal cavity. Behind these arteries are the internal spermatic vessels, the ureter, and the Psoas major. The sigmoid arteries can be damaged by thrombosis, meaning that blood clots can form, blocking the flow and preventing the circulation of blood. There are procedures that are used to take the thrombosis out of the arteries; the most commonly used treatment is catheter-directed thrombolysis because it is a nonabrasive surgery that works to dissolve the blood clot before it damages any tissue or organs.