Vomiting is triggered when the vomiting center, located in the medulla of the brain is stimulated by input from various receptors around the body. These receptors can be found in the gastrointestinal tract and organs such as the liver, pancreas, bladder, and pharynx. Cranial nerve VIII will stimulate the vomiting center if the animal has vestibular disease or motion sickness. The vomiting center can also be affected if the dog has a disease of the central nervous system. Once stimulated the vomiting center will then cause vomiting by triggering the stomach and diaphragm muscles to contract thereby forcing stomach and upper digestive tract contents up the oesophagus and out of the mouth.
Vomiting is often seen in dogs but it is usually only an occasional occurrence. If you notice your pet vomit only once then there is unlikely to be a problem. However, if vomiting is frequent or occurs over a period of more than a couple of days there may be an underlying problem which is causing it. The seriousness of vomiting depends upon any underlying cause and the severity and duration of the vomiting itself. If the vomiting is only occasional and does not go on for a very long time then there is probably little to worry about, especially if your pet is bright, alert and active. If your pet is dull, lethargic, inappetant or collapsed obviously there is a need to seek urgent veterinary attention. Also if your pet continues to vomit for longer than a day or two, or the vomiting is associated with other problems such as diarrhoea it would be wise to see your vet. If vomiting is prolonged or severe and goes untreated then it may lead to complications such as dehydration and malnutrition as well as chemical imbalances caused by the constant loss of fluids and nutrients.
There are a vast number of conditions which may cause vomiting in dogs but please remember when reading the rest of this article that the vast majority of vomiting pets do not have a serious underlying disease. I have tried to order the following discussion about the causes of vomiting so that the most common problems are discussed first. As you will see these are the least serious problems and also the most easily treated ones.
Dogs will often vomit because they have simply eaten too much or too quickly. In the wild it is natural for dogs to compete over food, so they have evolved to eat very quickly before other members of the pack get their share! If your dog seems to be eating very quickly and later vomiting it may be a good idea to feed him alone so that he does not feel a sense of competition which he may feel if fed alongside another dog. If this does not work then feeding him several small meals rather than one large one will usually sort the problem out. I have heard of the suggestion of putting really large pebbles in the bowl so that the dog has to eat around them; this would probably work but I think the risk of the dog swallowing a pebble and needing surgery to remove the foreign body is too high! Bitches may also regurgitate food for their puppies, this is a natural behaviour and is not something to cause concern.
Worms are another factor commonly causing dogs to vomit. Puppies tend to be affected most by roundworms which may cause a partial intestinal blockage that leads to vomiting; adult dogs may also vomit if they have worms and sometimes these worms will be present in the vomit and seen by the owner. Worming your dog every three months is a good idea if such problems are to be prevented. See Worming.
Vomiting can be caused by dietary factors, especially if your dog has a sensitive stomach. Sometimes dogs may not tolerate rich or fatty foods. It may be a good idea to use one of the Hills diets such as i/d or d/d if this is the situation with your pet. Alternatively a home prepared bland diet may be used such as cooked chicken and rice or white fish with pasta, although if these are used long term it may be necessary to give vitamin and mineral supplementation. Any changes to the diet should take place gradually over a period of about 10 days.
Colitis may cause vomiting, but the main sign will be diarrhoea which may appear to have mucus or blood in it. This condition which is seen frequently in dogs especially if they regularly scavenge for food will often resolve if a bland diet is given following 24 hours without food to rest the gut. See Colitis.
If vomiting is occurring frequently but there are no faeces being passed then you should visit your vet immediately because there may be a foreign body causing a blockage in the intestinal tract. Surgery is often required to remove such foreign bodies but occasionally they may pass on their own. However you should never delay in seeking advice from your vet because foreign body obstruction is a very serious problem which can even result in the death of affected animals if left untreated. Common foreign bodies found in dog's intestines include socks, shoes, leads, collars and toys. I once found a Kinder Surprise plastic egg in a dog's stomach complete with toy! The dog had obviously gulped down the chocolate egg together with the plastic capsule inside! Luckily this dog did well after the surgery and made a complete recovery.
If your pet has an infection of the stomach (gastritis) this will obviously cause vomiting. The upper intestine may also be affected so that the dog has diarrhoea as well. In this situation it is wise to starve the animal for 24 hours and introduce a bland diet with plenty of access to water throughout. Most such diseases are self limiting and will resolve in a few days. Remember that there are a few serious diseases which cause vomiting and diarrhoea which are zoonotic (humans can catch them) these include Salmonella, E. coli and Campylobacter so always wash your hands after handling your pet or their excrement or vomit. If cleaning up after a pet with gastrointestinal problems it would be wise to use gloves.
Liver, kidney and pancreatic diseases can all cause vomiting as can sepsis and metabolic imbalances. Disease of the central nervous system, congestive heart failure and cancer may also cause vomiting. All of these conditions are serious and will require veterinary treatment.
Many people come in to the veterinary surgery with a vomiting dog and are very concerned that their pet has been poisoned. This does occur but is not as common as many people seem to believe. It is difficult to treat poisoning if the vet cannot identify the actual poison ingested, so if you have the packet of the substance you believe your pet has consumed take it along with you when you go to the vet.
Gastric ulcers do occur in dogs and the bacteria Helicobacter pyloris has been implicated in this disease. If your dog is vomiting blood or has black tar like faeces this condition should be considered as a possible cause and urgent attention sought. Often dietary control is all that is needed in these cases but if they do not respond other treatment will be required.
The way in which vomiting is treated will obviously depend upon the cause and the severity of the symptoms. In the vast majority of cases the problem will not be serious and can be easily treated; however if your dog has a more serious underlying condition the outcome will of course depend upon the disease being diagnosed treated.
In uncomplicated cases of vomiting where the pet is bright, active, alert, passing faeces and not vomiting too frequently the dog is usually treated as an outpatient. Initially the animal is starved for 24 hours but offered plain water or Lectade to prevent dehydration. Over the next few days the dog may be given a bland diet such as chicken and rice or fish with pasta, or if preferred a special diet such as one of the Hills range may be given. Food should be given little and often in about 4-5 feeds per day over the next 3-4 days until the vomiting has resolved. Once the dog is better the normal diet should be gradually re-introduced over the next week or so. During this time it is a good idea to keep your dog on a lead during walks so that he cannot obtain food by scavenging and you can also observe the faeces and watch out for diarrhoea. If vomiting does not resolve during the first few days go to see your vet who may need to carry out some diagnostic tests. Remember to treat your dog for worms regularly.
If vomiting is severe enough to cause dehydration then your dog may need to be admitted to the veterinary hospital for fluids and other treatment to be given. In this situation every effort will be made to determine the underlying disease. Tests which may be carried out include blood sampling, x-rays, ultrasonography, endoscopy and faecal sampling.
Gastric dilatation and torsion is an extremely serious emergency situation which causes a dog to attempt to vomit continually, but only phlegm is produced rather than food or bile. The dog often appears to be in acute distress with continual attempts to vomit. Often the abdomen will be seen to markedly swell as the stomach fills with gas. Deep chested dogs such as German Shepherds and Great Danes are most often affected especially if they exercise after a meal. If you have the slightest suspicion of this in your dog call the vet, day or night and get your dog examined. Every minute counts with this serious and often fatal problem. Emergency surgery will be required to treat this condition.