Mar Vista Animal Medical Center

3850 Grand View Blvd.
Los Angeles, CA 90066




The signs of inflammation in the large intestine (also called the “colon”) are the same regardless of cause: a gooey, mucous diarrhea, straining to pass stool, cramping, and sometimes a surprise urgency to “go.” These symptoms can be acute (as is common with a short term stress like boarding, return from boarding, or diet change) or they can be chronic as with whipworm infection or inflammatory bowel disease.

Many people get confused between inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS). Inflammatory Bowel Disease is a physical disease where the intestinal lining is infiltrated by inflammatory cells. The delicate intestinal lining becomes thickened and absorption of nutrients becomes altered. The infiltration can be seen under the microscope and this is how the diagnosis is confirmed. Inflammatory Bowel Disease is a completely different disease from Irritable Bowel Syndrome.

Normal Large Intestine

 Normal Large Intestine (albeit human)

(Photocredit: Josef Reischig via Wikimedia Commons)


colon with lymphocytic infiltration

colon with lymphocytic infiltration -
"Inflammatory Bowel Disease"
(This is not Irritable Bowel Syndrome)
Photocredit: Nephron via Wikimedia Commons)



IBS is a psychosomatic disease. It is the activity of the mind that causes the symptoms. Most people have had some kind of experience where stress has produced intestinal distress, be it cramping, nausea, diarrhea or all of the above.

Chronic anxiety can similarly result in chronic diarrhea. This is basically what IBS is all about. Intestinal biopsy results are normal because there is nothing directly wrong with the large intestine. The process is the same whether the patient is human or non-human.

Large intestinal diarrhea in veterinary patients can have many causes and IBS is afoot in about 10-15% of cases. It is important to rule out physical causes before blaming psychological reasons but if all tests are normal and treatment for physical problems is not yielding results, this is when a biopsy is helpful. Again, a normal intestinal biopsy rules in IBS. It should be noted that fresh blood in the diarrhea is common with large intestinal diarrheas but so much with the large intestinal diarrhea of IBS.  Fresh blood in the diarrhea is a sign that there is a physical cause and not a psychosomatic cause. Knowing this can help direct the medical approach.



The obvious approach is to address the anxiety. The source of emotional stress may not be obvious but general anti-anxiety medications such as amitriptyline, clomipramine, or fluoxetine may be of use, particularly if the anxiety source is not clear or cannot be removed. Some patients will respond to supplements as listed below. It is important to imagine the pet’s world from his/her own perspective. The pet does not speak English and must infer what is going on from events he or she witnesses directly. Inconsistent scheduling, moving to a new home, noisy construction nearby, or even weather changes can be very confusing for an animal.

More commonly, however, IBS is addressed via the GI tract rather than via the psyche. Increasing dietary fiber is helpful to many IBS patients as fiber has been found to help normalize the spasms of the large intestinal muscles and many therapeutic high fiber diets are sold through veterinary hospitals. If your pet finds these unpalatable, ask your veterinarian about how to add wheat bran or a commercial fiber supplement to a diet your pet prefers. There are presently several commercial dog foods that contain calming supplements. Using one of these plus a fiber supplement might cover both the fiber angle as well as the anxiety.

Hills WD Canine Food

Hills prescription food

Royal Canin Feline food


For many patients, cage rest or tranquilizers allows for enough rest to control symptoms. Antispasmodics or general anti-diarrhea medications such as loperamide, azulfidine, or metronidazole can be used on an "as needed" basis to control signs.

A number of supplements have recently been marketed to address anxiety (not to mention pheromone products). These are not as strong as prescription drugs but are available without prescription for those who wish to try them:

Alpha Casozepine - This is a milk protein with natural calming properties. It is available as an oral supplement (Zylkene®) for pets or in special calming pet foods (Royal Canin Calm Diet®, Hills Urinary Stress C/d for cats®).

L-Theanine - This is a derivative from green tea and is available in capsules as well as flavored chews (Anxitane®, Solliquin®, Composure®).

Adaptil Defuser and Collars - Dog Appeasement Pheromone or D.A.P. is naturally secreted by mother dogs to communicate safety and security to her litter of puppies. This pheromone has been synthesized and is available as a room spray, plug in wall defuser, and as an impregnated collar that the dog can wear. This gives the anxious dog a message in his or her own language that there is nothing to be anxious about.

Cannabinoids - These are obviously of controversy and are not presently legal except as hemp products which may be appropriate. CBD is commonly marketed for pets but at the present time none of the recent legalization efforts have included pet products and quality control is lacking at the present time.


Consult your veterinarian if you wish to pursue one of these therapies but keep in mind that Irritable Bowel Syndrome is not diagnosed until a medical work up for physical causes of large bowel diarrhea has come up empty.


Page last updated: 520/21