A simple definition of small intestinal bacterial overgrowth (SIBO) is the presence of abnormal and excessive numbers of bacteria in the small intestine. Although the veterinary community characterized SIBO several decades ago, there still needs to be a consensus among medical experts on the best diagnostic technique or the optimal treatment of SIBO.

The role of the small intestine, as food enters it, is to continue the digestive process initiated in the stomach and begin the nutrient extraction and absorption process. The food is mixed with enzymes and other chemicals produced in the liver, gallbladder, and pancreas.  The walls of the small intestine are lined with tiny projections, villi, that contain the capillaries, through which the digested food particles are absorbed and then carried to the rest of the body via the bloodstream.

Bacterial colonies that inhabit the mucosa aid in the breaking down of the partially digested food to prepare it for absorption into the bloodstream. However, when SIBO occurs, the imbalance of the bacteria types prevents this critical phase in the digestive process, leading to malabsorption and malnutrition. 

Nutrient absorption in dogs primarily occurs in the small intestine, divided into three sections: the duodenum, jejunum, and ileum. The small intestine is the primary site for absorbing nutrients from the digested food, including proteins, carbohydrates, fats, vitamins, and minerals.

The duodenum is the first segment of the small intestine, where partially digested food from the stomach mixes with digestive enzymes from the pancreas and bile from the gallbladder. These enzymes further break down nutrients into smaller, absorbable molecules.

Most nutrient absorption occurs in the jejunum, the middle segment of the small intestine. The jejunum is characterized by numerous finger-like projections called villi and even smaller microvilli on the surface of the intestinal lining. These structures significantly increase the surface area for nutrient absorption.

The ileum is the final section of the small intestine, and it continues to absorb any remaining nutrients, especially vitamin B12 and bile salts. It also helps transport digested material into the large intestine (colon).

The absorbed nutrients are then transported via the bloodstream to various cells and tissues in the dog's body, where they are used for energy, growth, and maintenance of bodily functions.

The large intestine primarily absorbs water and electrolytes from the undigested material, forming feces. 

Small Intestinal Bacterial Overgrowth occurs when there is an abnormal increase in the population of bacteria in the small intestine, where there should typically be fewer bacteria compared to the large intestine. Several risk factors can contribute to the development of SIBO in dogs.

SIBO can develop due to the reduction in gut motility (dysmotility). Several medications slow gut motility, including narcotics, anticholinergics that inhibit acetylcholine signals, which prevent muscles from contracting, and antidiarrheals.

Diseases and disorders that cause small bowel dysmotility are IBD, obesity, neurologic problems, gastrointestinal obstruction, intestinal parasites, and peritonitis. Chronic pancreatitis can also lead to SIBO because the decrease in the secretion of digestive enzymes alters the digestion and absorption of nutrients.

Anatomical abnormalities such as unusual crevices or pouches within the intestinal wall can create areas for SIBO to develop. These crevices are called diverticula, and the condition is diverticulitis when inflamed.

After a surgical procedure, especially those involving the stomach or small intestine, your dog’s intestinal tract may experience a reduction in motility, which increases the risk of SIBO. Surgery and other underlying conditions can impair your dog's immune system, which makes the gut more susceptible to bacterial overgrowth. 

If your dog has certain systemic diseases, such as diabetes mellitus or kidney disease, she may be more prone to developing SIBO.

Evidence shows that the German Shepherd Dog has a higher incidence of malabsorption problems. They often experience malabsorption in conjunction with exocrine pancreatic insufficiency (EPI). SIBO has occurred either with or without EPI in shepherds.

Your dog may not have all these signs, but those exhibited are usually chronic. Malabsorption of food is a primary consequence of SIBO.  Malabsorption leads to weight loss, anemia, and deficiencies in vitamins and minerals. Young dogs afflicted with SIBO have stunted growth and a failure to thrive.

Lack of energy and constant hunger are other outcomes of malabsorption. The continuous urge to eat can lead to pica, craving and ingesting strange non-food items.  

Due to malabsorption of nutrients, dogs with SIBO may have a dull, dry, or scruffy coat. 

Your dog may exhibit signs of abdominal pain accompanied by bloating and gas (flatulence). Chronic diarrhea and vomiting will lead to dehydration. 

The clinical signs of SIBO can overlap with those of other gastrointestinal disorders, making it essential to consult a veterinarian for an accurate diagnosis. 

No single easy test is available to diagnose SIBO, but rather a series of tests to determine the causes of your dog’s clinical signs and eliminate other possible disorders. Many of these tests are complex, expensive, and often inconclusive. 

Your veterinarian will start by taking a detailed history of the dog's clinical signs, including the duration and nature of gastrointestinal issues, changes in appetite, and any other relevant information. A physical examination and routine bloodwork should be performed to assess your dog's overall health. 

Regular blood work that includes a complete blood count (CBC) and a chemistry profile is performed to rule out other diseases. Serum TLI (trypsin-like immunoreactivity) assay is another blood test that can be performed to rule out exocrine pancreatic insufficiency (EPI). 

A breath hydrogen test is one of the most reliable measures of SIBO. The test involves administering a substrate (such as lactulose), which is fermented by bacteria in the small intestine. Elevated levels of hydrogen or methane in the dog's breath following substrate ingestion can indicate bacterial overgrowth. However, only a few veterinary clinics are equipped to run this assay as it requires a specific device, and it is difficult to get cooperation from most dogs.

Your veterinarian should also analyze a stool sample to check for parasites and higher-than-normal bacteria levels in your dog’s feces. To rule out bowel obstruction, she can also conduct diagnostic imaging such as radiographs (x-rays), ultrasounds, or endoscopy. Endoscopy can help identify mucosal changes, inflammation, or other abnormalities associated with SIBO.

The duodenal juice test is performed using an endoscope and under sedation.  The endoscope is passed into the small intestine, and material is collected for analysis. Many dogs will still test normal despite this being considered the best diagnostic tool for SIBO.

Most veterinarians will want to treat SIBO with long-term antibiotics. However, this can lead to other intestinal issues because antibiotics further damage the gut microbiome. The holistic approach treats the root cause by repairing the gut microbiota.

Begin the treatment of the gut microbiome by feeding your dog prebiotics and probiotics . For a dog’s gut to truly heal, they need a combination of prebiotics and probiotics.  If probiotics are given to unprepared gut flora, without the concurrent use of prebiotics,  they will be less likely to colonize the mucosal lining and eventually die off.  By preparing the gut with prebiotics, food that feeds the bacteria in probiotics, the probiotics will flourish and start crowding out the harmful bacteria. 

Prebiotics are soluble dietary fibers that withstand digestion throughout the GI tract until they enter the colon undigested. In the colon, they ferment and create short-chain fatty acids (SCFA) that stimulate the growth and activity of the body’s beneficial bacteria. Prebiotics improve the composition of the gut flora by providing food for the beneficial bacteria, decreasing inflammation, supporting the immune system, and reducing the overall risk of disease. 

Examples of prebiotics to add to your dog’s bowl include medicinal mushrooms , chicory root,

garlic, larch arabinogalactan, burdock root, dandelion greens, apples, bananas, and asparagus.

Probiotics are healthy bacteria that aid in restoring a dog’s gut microbiome. They are supplied in fermented foods or as supplements. Microorganisms used for probiotics must pass the stomach–duodenum barrier without being destroyed to multiply and thrive in the large intestine. 

Lactobacillus and Bifidobacterium are the two most widely known bacteria used as probiotics.  Both of these are usually produced from fermented milk products.

The probiotic yeast Saccharomyces boulardii treats acute and chronic diarrhea and other digestive issues caused by chronic gut inflammation. This strain is also known to be antibiotic-resistant.

Bacilli strains of probiotics are spore-forming bacteria that overcome harmful bacteria in the gut. With their anti-inflammatory properties, they are used for inflammatory digestive diseases.

Akkermansia muciniphila has recently been shown to have remarkable benefits for dogs.  It promotes a healthy GI mucosal lining and supports the motility within the GI tract. This, in turn, prevents diarrhea and irritable bowel syndrome (IBS).

The two popular probiotic foods for people, kefir and fermented foods, are too difficult for SIBO dogs to digest. Dairy is hard for dogs afflicted with SIBO to digest due to the damage to the intestinal wall. The damaged mucosa causes a reduction in the production of lactase, the enzyme that digests lactose in dairy foods.  

The best option for probiotics for dogs with SIBO are probiotic supplements formulated for dogs. The probiotic supplement should also contain prebiotics. Look at the label for “Contains Prebiotics” or a list of prebiotic foods in the ingredients.

Probiotics need to be provided in the proper amount to be effective. Lactic acid bacteria are easily destroyed in the gut, so they must be supplied in large amounts, at least 10 billion CFU (colony forming units) for a healthy dog and up to 25-50 billion CFU for dogs suffering from digestive issues or immune disorders. Saccharomyces boulardii can be provided in 5 billion CFU. Bacillus strains can be supplied at 1 billion CFU.

The commercially available capsules of probiotics are dehydrated bacteria reanimated when rehydrated. The contents of the probiotic capsules should be mixed with two tablespoons of full-fat plain yogurt and filtered water. Provide the mixture to the dog between meals on an empty stomach. Do not add to the dog’s meal, as the digestive enzymes in the stomach will deactivate the bacteria. Because it is a liquid, the yogurt and water mixture will pass through the stomach quickly, avoiding the negative impact of the stomach acid and digestive enzymes on the bacteria.

Several herbs can offer relief, speed up your dog’s digestive tract recovery, and help manage diarrhea . Slippery elm is a soothing herb that calms mucous membranes. It is a safe, gentle, and effective herb for your dog's inflamed intestines. 

Although slippery elm is an excellent herb for calming diarrhea, the tree is now endangered due to the Dutch Elm disease that has ravished the elm population in the United States. Marshmallow root should be used instead whenever possible.

Marshmallow root is good for calming the gastrointestinal tract and reducing inflammation. Providing this herb to your dog will reduce inflammation, increase urine production to remove excess water in the body, inhibit the growth of bacteria, viruses, and fungi in the intestines, and boost the immune system.

Transitioning to a raw, whole-food diet that includes lean protein, leafy greens, and other non-starchy vegetables will also aid in healing the gut microbiome. While treating SIBO, avoid feeding fruits, grains, legumes, and starchy vegetables because they convert to sugar upon digestion, which will feed the bacterial overgrowth. 

The ideal diet will contain the six critical components of the Real 6x Ancestral Diet™ : 63-65% lean muscle meat, 10-12% raw meaty bones, 10% seafood, 5% liver, 5% other secreting organs, and 5% fur or other fiber from non-starchy vegetables. 

The transition  to a fresh food diet will need to be gradual, and gentle cooking of the food may be required to encourage your dog to eat and aid in digestion. 

Become comfortable observing your dog’s poop , as it can reveal much about what is happening inside the body. As your dog’s gut microbiome heals and is recolonized with beneficial bacteria, you will notice drastic changes in your dog’s poop!  

A simple definition of small intestinal bacterial overgrowth (SIBO) is the presence of abnormal and excessive numbers of <a href="https://feedreal.com/glossary/bacteria">bacteria</a> in the small intestine. Although the veterinary community characterized SIBO several decades ago, there still needs to be a consensus among medical experts on the best diagnostic technique or the optimal treatment of SIBO.

Small Intestine Bacterial Overgrowth in Dogs

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