As you know, most cats, being both playful and predatory in nature, love to play with string. Although this can be a fun way for us to interact with them, string can be quite dangerous for cats if it is ingested. Linear foreign bodies can be difficult for the veterinarian to diagnose and a delayed diagnosis can have a poor outcome in this situation.
Routine x-rays often are inconclusive and exploratory surgery is generally required to save the cat’s life. String will usually not pass through a cat’s digestive tract and, if not surgically removed, bowel penetration or peritonitis can result. So please, if your cat plays with any linear string objects, make sure it is supervised play.