X-Ray Vision

If my dog eats something he shouldn’t, will it show up on an X-ray?

Vomiting and loss of appetite are common reasons to bring your dog to the veterinarian. Recognizing signs on an X-ray of an obstruction of the stomach or intestines is an important skill your veterinarian has learned. Some foreign bodies can be identified even without the presence of a blockage, and monitoring with serial radiographic studies can confirm their passage into the colon. Once an object has passed into the colon, it should be excreted without a problem.

Rubber – Rubber objects are radiopaque, which means they will be visible on an X-ray, especially if they are large enough pieces. The mineral content of the rubber makes them appear white on the image. The higher the mineral content, the more “opaque,” or white, the object appears. This can be useful when there is known or suspected ingestion of specific rubber foreign material, such as hair ties or tennis balls.

Radiographs can quickly determine the presence of rubber material. Rubber balls are often hollow and may appear as complete or semi-collapsed mineral opaque circles with gas-filled centers. Tennis balls are typically chewed into fragments before swallowing and will often appear as curved cylindrical mineral objects, often with jagged edges.

Last week, I removed an object that was obstructing the intestines of a young Doberman. From the long, sharply pointed shape of the foreign body on the radiograph, I was expecting a bone to be lodged there and was concerned about perforation of the intestine. Luckily, it was a tennis ball squashed into the shape of a bone. The dog recovered nicely.

Rubber bands, hair ties and scrunchies are commonly eaten by dogs of all ages. Like rubber balls, these are usually able to be detected on X-rays. They appear as linear mineral opacities that may or may not form complete rings. Dogs can pass one or two of these. When they swallow multiple ties or if the ties accumulate in the stomach over time, surgery may be needed to remove them.

Corn Cobs – Corn cobs that get stuck in the stomach or intestines are common, especially during fresh-corn season (summer to early autumn). If the dog chewed the corn cob into small pieces, it would likely be unidentifiable as corn cob, essentially looking like normal digested food. However, if the corn cob segment was swallowed whole or in large pieces, it may be readily visible on radiographs.

The most common appearance of a corn cob is of a rectangular or cylindrical object of mixed soft-tissue and gas opacity, with a pattern of stippled gas regularly spaced in a grid that has the appearance of corn kernels on the cob. The “sockets” that hold the corn kernels will entrap gas, creating this grid pattern seen on the X-ray.

Corn cobs frequently cause intestinal obstructions that can be challenging to diagnose. The dog may be able to keep water and liquids down, but vomit food intermittently. This is because the center of the corn cob hollows out, allowing fluid and some food to pass. The shell of the cob gets wedged in the intestines and will cause irritation and damage until it is surgically removed. An ultrasound or contrast study with barium may be needed to diagnose a retained corn cob-section.

Stone Fruit Pits – The pits from peaches, plums, apricots and other similar stone fruit have a particular appearance radiographically. They are almond-shaped, mixed-opacity objects, usually with a clear gas center and a wall that is soft tissue to mineral opaque. The wall of the fruit pit is only faintly mineral in opacity. When surrounded by fluid, it can be a very subtle lesion, as the gas spots in the center can resemble normal intestinal gas. The ridges of the pit can also create lines of opacity over the gas center, creating a slightly striped appearance.

Tree Nuts – Certain tree nuts with strong shells or coats, such as chestnuts, walnuts, pistachios, hazelnuts and acorns, can be seen on X-rays. These are less common as obstructive foreign bodies, unless they are large in proportion to the dog or consumed in large amounts. They may also cause irritation as they pass through the digestive tract.

Tree nuts tend to be more challenging to identify, as they do not have a hollow center, unlike stone-fruit pits. The shell and the nut meat are usually of a soft-tissue opacity. Some gas can be present between the shell and the nut meat, creating a distinct outline of the foreign body.

Fabric – Dogs are always eating socks, underwear, towels and other pieces of fabric. The fabric foreign material is generally of a soft-tissue opacity with numerous characteristic striations that distinguish it from normal stomach and intestinal contents. Fabric foreign material may cause gathering of the intestines, known as plication (think of the shape of a scrunchie), depending on whether frayed threads create a linear obstruction. The fabric can also mimic formed feces in the colon, as there is often some amount of entrapped gas and an amorphous, tubular shape.

Hairballs – While more common in cats, hairballs can also form in dogs. The medical term for a hair ball is trichobezoar. They can cause obstruction of the stomach or intestines, especially in dogs with an underlying condition such as inflammatory bowel disease or lymphoma.

Hairballs can be very challenging to positively identify on radiographs, as they have a fairly nondescript appearance and tend to blend in with the normal intestines. They are characterized by a somewhat stippled gas pattern with an otherwise soft tissue opacity. It is almost impossible to distinguish hairballs from normal stomach contents or formed feces in the colon. Thankfully, they are more likely to pass with lubricants and fluid therapy than other obstructive foreign bodies.

Bismuth Subsalicylate (Pepto-Bismol) – Although technically not a foreign body, it is good to know that due to the bismuth, which is a metallic element with an atomic number of 82, Pepto-Bismol and other bismuth-based stomach-coating medications will have a radiopaque appearance of a metal or mineral substance. This usually only becomes an issue if a client has given the medication in tablet form and did not inform the veterinarian.

In liquid form, the bismuth rapidly dilutes and may simply look like a small amount of non-obstructive granular mineral material. As an intact tablet, however, Pepto-Bismol very much resembles a foreign body, like a coin or a stone. This can be a cause for concern to the veterinarian, who may schedule an emergency surgery to remove the foreign bodies. Based on how long it takes Pepto-Bismol tablets to dissolve in a dog’s stomach, they do not appear to be an effective treatment anyway.

The presence of an identifiable foreign body does not automatically mean surgical exploration is needed. Many foreign bodies that are non-obstructive can pass with supportive care, including electrolyte fluid therapy. Being able to identify what type of foreign body is present on the radiograph helps your veterinarian formulate the best plan for successful treatment.