Foreign body syndrome is an inflammatory disease, caused by the ingestion of a perforating foreign body, most often metallic. Adult dairy cattle are most affected. Depending on the direction that the foreign body takes when it reaches the reticulum, it can reach adjacent organs and cause reticulum peritonitis or reticulum traumatic pericarditis. It can cause unspecific signs such as fever, changes in rumen motility and cardiac signs. The diagnosis consists of observation of clinical signs, evidence of pain, ultrasound, hematology, blood biochemistry and analysis of cavitary effusions. The treatments normally used are conservative, with or without magnet and rumenotomy.