Malabsorption and Bacterial Overgrowth in Dogs

By Tammy Hunter, DVM; Ernest Ward, DVM

What is malabsorption and bacterial overgrowth?

Bacterial overgrowth is a condition of the small intestine resulting in increased numbers of bowel bacteria. The major concern with bacterial overgrowth is the development of a condition called small intestinal bacterial overgrowth (SIBO).

The bacteria cause damage to the absorptive surface of the bowel so digested food cannot be absorbed through the bowel and into the body, resulting in malabsorption of nutrients.


Is this the same as an infection causing enteritis?

Malabsorption and SIBO both result in diarrhea, similar to that associated with enteritis. However, with bacterial overgrowth the diarrhea is chronic in nature, often lasting weeks or months.


Are some dogs more susceptible than others?

German Shepherds appear to have a higher incidence of malabsorption problems. These problems are frequently associated with exocrine pancreatic insufficiency (EPI) but SIBO can occur either with or without EPI. See handout “Exocrine Pancreatic Insufficiency in Dogs” for more information about this condition.

What are the common clinical signs of malabsorption?

The principal sign is weight loss with chronic diarrhea. Most dogs will have a normal or increased appetite but continue to lose weight.

Can it be differentiated from pancreatic insufficiency based on the symptoms?

Specific blood and fecal tests are necessary to differentiate EPI and SIBO. Dogs with malabsorption often do not have as voracious an appetite and the diarrhea is usually not as voluminous as EPI.

What is the cause of this condition?

Many cases are idiopathic (unknown cause). SIBO is frequently associated with exocrine pancreatic insufficiency (EPI).

Can the condition be cured?

Many cases respond to long term antibiotics. Tylosin (Tylan®), oxytetracycline and metronidazole (Flagyl®) are common antibiotic choices that are usually combined with special diets to treat this condition. In cases of primary SIBO without any complicating factors, the prognosis is usually good.

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