Dogs swallow foolish things, some of which are not digestible and form blockages. These include toys, bones, pebbles, fruit stones, corn cob, fabric, food wrappers and just about anything else handy. Small items usually pass through uneventfully, accompanied by soft stools or diarrhea. Foreign objects that have left the stomach but ground to a halt in the first part of the intestine usually cause vomiting. There is associated pain if the pancreas is disturbed. Other items lodge at the junction between the small and large intestine. In pups in particular the small intestine can telescope into the large intestine causing an intussusception, a complete blockage. Because this is extremely damaging to the telescoped tissue, clinical shock develops.
Foreign bodies such as peach stones are capable of moving through the intestines but them grinding to a halt almost anywhere causing pain and vomiting. There may be associated diarrhea. Foreign bodies with string or other material attached are particularly common and damaging to cats. The object can anchor in one location and the extended string acts as a saw within the intestines, eventually breaking through the wall of the intestines producing a life-threatening peritonitis. Tumours are uncommon. Initially they act like partial obstructions and lead to a decreased motility of the intestines.
Intestinal obstructions, including intussusceptions can often be felt through the abdominal wall, especially in pups and young pets. Plain or contrast x-rays are useful in fat pets or for partial obstructions. Partial obstructions can be particularly difficult to diagnose even with contrast x-rays. Surgery is usually needed to remove the foreign body. When tumours are present the lungs and liver are x-rayed for secondary tumours before surgical correction is undertaken.