Intestinal foreign bodies can come in all shapes, sizes and contents. While some objects like rocks and bones will show up clearly on plain radiographs, there are many other materials that do not. These include, but are not limited to: Vegetable matter (corn cobs, seeds and nuts), many rubber and plastics (chew toys, kongs, tennis balls), and materials (cloth, towels, cotton wool, hairballs, cardboard).
Clinical signs associated with intestinal foreign bodies can be wide and varied. Inappetance, vomiting and lethargy are most common but are not always present or witnessed. It is surprising how often dogs with intestinal foreign bodies are not witnessed to be vomiting. A large percentage of dogs with an intestinal foreign body will be diagnosed or taken to exploratory laparotomy based on history, prior behaviour, abdominal palpation, abdominal xrays and electrolyte/biochemistry changes. In a number of cases these tests, history and physical examination are not definitive. This is where abdominal ultrasound can be very valuable in confirming that surgery is required, or just as importantly, giving confidence that surgery is not required and that further medical management is appropriate.
The confident identification of intestinal foreign bodies causing obstruction takes a high level of experience with diagnostic ultrasound and a detailed abdominal examination. Suggestive signs of an intestinal obstruction are a fluid distended stomach, fluid filled, dilated small intestines oral to the obstruction and normal, empty small intestine distal or aboral to the obstruction. Seeing these signs should direct the ultrasonographer to thoroughly interrogate the intestines for an obstruction. The key to confirming a diagnosis of an intestinal foreign body causing obstruction is documenting the foreign body. The foreign body will be identified by an ultrasound artefact known as attenuation. This is where the ultrasound beam is highly reflected at the surface of an object and does not penetrate distal to the surface. Complicating matters is that gas and faeces will also cause attenuation. It is important to be able to image the area of attenuation with dilated intestine orally and normal intestine aborally. The intestinal wall should be stretched over the foreign body. Expansion of the small intestinal wall with disruption of the normal layering is an indication of a mass lesion rather than an intraluminal obstruction. Surgery is now indicated as soon as fluid resuscitation and electrolyte imbalances are restored. This case turned out to be a corn cob. No vomiting was seen by the owners.