Dogs that swallow string can develop a linear foreign body. The string does not move through the intestines as a whole--it gets stretched out through the intestines. This causes the intestines to plicate--bunch up together. The more the intestines try to pass the string the more bunched up they become. Usually by the time foreign bodies are in the colon they pass--dogs are able to defecate them out. With this situation it depends how long the string is.
I would not try to pull it out if that makes your dog painful. Give your dog canned pumpkin or whole wheat/grain bread--the fiber can help bulk the diet and sweep things through the intestine.
I am concerned that he is acting lethargic. It would be best to have him examined by a veterinarian and have x-rays taken if appropriate. If he has not passed the string in 12-18 hours he needs to go to the veterinarian ASAP. The bunching of intestines can lead to intestinal death and is an emergency.
I would not try to pull it out if that makes your dog painful. Give your dog canned pumpkin or whole wheat/grain bread--the fiber can help bulk the diet and sweep things through the intestine.
I am concerned that he is acting lethargic. It would be best to have him examined by a veterinarian and have x-rays taken if appropriate. If he has not passed the string in 12-18 hours he needs to go to the veterinarian ASAP. The bunching of intestines can lead to intestinal death and is an emergency.