Excessive Bacteria in the Small Intestine in Dogs

Although it is necessary for your dog to have some bacteria in the intestines for digestion, an excessive amount of bacteria can lead to health problems. These bacteria injure the absorbent surface of your dog’s bowel so that the food eaten is digested, but cannot be absorbed into the bowel. The result of this is that your dog does not get nutrients from the food he is eating (malabsorption).

This condition seems to occur more often with dogs who have exocrine pancreatic insufficiency (EPI), which is when your dog is unable to digest food correctly because the pancreas is not making enough digestive enzymes. When the bacteria are able to use the undigested food to live and multiply they take over the intestinal tract, causing more damage. If the EPI and small intestinal bacterial overgrowth are not treated right away, your dog can end up with chronic digestive problems.

Excessive bacteria in the small intestine is also called SIBO (small intestinal bacterial overgrowth) or SID (small intestinal dysbiosis), but these are all the same disorder that is described as the overgrowth of bacteria in your dog’s small intestine. This disorder can cause many symptoms related to digestion (diarrhea, gas, vomiting) and SIBO can be caused by several things, but most often the cause is unknown. It can happen in any breed, sex, or age, but young German Shepherds are the most commonly affected by SIBO.

The main symptoms of small intestinal bacterial overgrowth are digestive problems that can be overlooked when mistaken for some other illness, leading to more problems if not treated promptly. The most common symptoms of small intestinal bacterial overgrowth are:

• Large amounts of loose stools
• Weight loss
• Vomiting
• Passing gas
• Stomach gurgling or growling
• Failure to thrive
• Normal or increased appetite
• Abdominal pain

 Types

There are two types of small intestinal bacterial overgrowth, which are idiopathic SIBO (small intestinal bacterial overgrowth with no other underlying illnesses), and secondary SIBO which is a small intestinal bacterial overgrowth that occurs with other intestinal diseases, such as exocrine pancreatic insufficiency (EPI).

This disorder seems to affect young German Shephard and other large breed dogs, but can happen in any breed, age, or sex. Most often, the veterinarian cannot find the reason for SIBO when it is idiopathic. Secondary SIBO is suspected to be caused by any one of these:

 Lack of Forward Intestinal Movement (ileus)

• Neurologic problems
• Gastrointestinal obstruction
• Pancreatitis
• Peritonitis
• Parasitism

Excess Food Backup

• Exocrine pancreatic insufficiency (EPI)
• Other food absorption deficiencies

Malnutrition

• Not being fed the proper food or amount of food
• Congenital deficiencies
• Lymphangiectasis
• Too much fat and protein
• Villous atrophy
• Loss of digestive enzymes

Altered GI Motility

• Partially obstructed intestine
• Paralytic ileus
• Anatomical disorders

The veterinarian will need to do a thorough physical examination of your dog including body temperature, weight, heart rate, blood pressure, and palpation of the abdomen. The veterinarian will need to know what symptoms you have noticed, when they started, if they have gotten worse, any recent illnesses or injuries, and if you have started any new foods recently. The veterinarian will also need to run some laboratory tests to rule out other illnesses. These tests are CBC (complete blood count), biochemical profile, urinalysis, stool sample, bacterial and fungal cultures, parasitic tests, and digital radiographs (x-rays). The veterinarian may also want to perform an endoscopy, which requires sedation. An endoscope is a small tube with a camera attached that the veterinarian inserts into the stomach through the mouth or colon (rectum). This allows him to check the esophagus, stomach, and intestines for obstructions and any other abnormalities. The veterinarian can also get a sample of duodenal juice for a culture to find the amount of bacteria involved. If an obstruction is suspected, the veterinarian may need to do an ultrasound, CT scan, and MRI. Serum folate and cobalamin assays are helpful to diagnose SIBO as well.

Your veterinarian may first want to try putting your dog on an antimicrobial therapy diet for about a month to see if this helps. If treatment is still needed, there are several antibiotics that your veterinarian may prescribe, such as metronidazole, tylosin, and oxytetracycline to treat the disorder. A special low-fat diet can help relieve the diarrhea and the veterinarian may prescribe a limited antigen diet to reduce sensitivity to the bacteria. The underlying illness may be more difficult to treat, depending on the diagnosis. Some veterinarians may give an anthelmintic (parasitic drug such as fenbendazole) in case of a parasitic infection.

Recovery will depend on whether your dog has idiopathic or secondary SIBO. With secondary SIBO, the disorder should go away after the underlying illness is treated. However, idiopathic can be more difficult to treat because the illness tends to return when the medication is stopped. Your dog may need long-term or lifelong medication treatment.