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Intestinal obstructions are common in dogs

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Corncobs are a common cause of intestinal obstruction in dogs

Corncobs are a common cause of intestinal obstruction in dogs

Corncobs are a common cause of intestinal obstruction in dogs

Vets are often faced with a problem that's rare in the world of human medicine: objects getting stuck in the digestive tract. I've seen three cases in the past few months, each presenting a different challenge.

Dogs are the main culprits: cats are far more fastidious eaters, cautious about what they chew and swallow. Dogs just grab and gulp, leading to all sorts of complications.

The main problem, of course, is that dogs don't understand that there are some objects that just should not be swallowed. They get carried away in the moment, enjoying chewing something, and almost without realising it, they swallow the object.

The back of the mouth and oesophagus are relatively capacious and able to stretch, so even large objects can be swallowed, making their way down into the stomach. However the digestive tract gets narrower after that: the exit from the stomach is difficult for any solid object much larger than 2 - 3cm to get through, and the small intestines are even narrower.

The digestive tract is like a one way conveyor belt: once an item has reached the stomach and intestines, it cannot go back. In theory, a large object that is in the stomach may be able to be regurgitated, but that's exceptionally rare.

In other cases, the strong acid in a dog's stomach may be able to digest a solid object (such as a soft piece of bone). But in most instances, once an indigestible item enters the stomach, it has to pass through the intestines, to emerge in the faeces. If it's too big to do this, it gets stuck, causing a life threatening crisis.

One of the challenges in cases like this is that the owner of the animal often does not know that their pet has eaten anything that might cause a problem. Dogs often find objects when on their own, and although an owner might sometimes notice that a toy has gone missing, or the end of a bone being chewed has broken off and disappeared, these are the exceptions.

More commonly, owners may know that their pet has a tendency to chew and swallow objects: some dogs have a history of being repeat offenders, needing to have objects surgically removed on multiple occasions.

Repeated vomiting is the most common sign of illness with an intestinal obstruction. It's common enough for a dog to have an isolated incident of vomiting, but when a dog vomits multiple times over 12 to 24 hours, there's often a serious cause that needs to be investigated.

Affected animals often get dehydrated, becoming dull and inactive, and appearing obviously ill. They usually stop eating too, and sometimes they want to drink copiously, even though they may vomit up the water soon after drinking. It's important that animals showing these signs are taken to the vet without delay.

As a vet, the history of a case like this is often enough to raise the suspicion of an obstructing gastrointestinal foreign body.

Sometimes a physical examination of the patient is enough to confirm the diagnosis: a solid mass can be felt in the intestines (if you can imagine a golf ball inside a soft fabric bag, that's what it feels like). In most cases however, it isn't so easy: the dog may tense their abdominal musculature, which makes it a bit like trying to feel for a golf ball inside a rigid, hard-walled box. Further investigations are needed, and an x-ray picture is often the key diagnostic tool.

In the first case I saw recently, an x-ray made the diagnosis easy: the Spaniel had swallowed a large stone, and this could clearly be seen on the x-ray as a large solid white object in the middle of the abdomen. I knew as soon as I saw this that immediate life saving surgery was needed.

The second case was more complicated: the dog had swallowed a corn-on-the-cob, and this type of object does not show up clearly on x-rays. The density of a corncob is similar to the other normal structures in a dog's abdomen.

However when an object causes an obstruction in the intestines, large quantities of gas build up, creating black oval and tubular shapes on the x-ray. When I looked at the x-ray of this second patient, I could see a suspicious, well-defined cylindrical shadow at the centre of the build-up of gas. This was enough to convince me that urgent surgery was necessary, and half an hour later, a bedraggled, half-digested piece of corn cob had been removed.

The third case was even more complex: again, the vomiting, dull, dog had x-rays taken, but this time, there was neither a solid white stone-like object, nor were there obvious areas of black oval or tubular shapes or vague corncob type shadows. So what was going on? On close examination, an unusual scattering of smaller black bubbles could be seen on the x-ray, but that isn't enough to make a definite diagnosis.

An ultrasound scan of the dog's abdomen was the next stage, and this gave the answer: a distinct abnormal line could be seen in the middle of the intestines. This was a clear indication of a so-called "linear foreign body".

An hour later, I pulled out a long piece of string that had been wrapped around a joint of meat when the dog had stolen it. One knotted end had stuck in the stomach while the rest had moved down the intestines. This was a classic "partial obstruction" which is particularly difficult to diagnose.

The good news is that surgical removal of obstructions of this type is usually sucessful. The next challenge, of course, is how to make sure that it doesn't happen again!

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