Infiltrative Bowel Disease in Cats

What does Infiltrative Bowel Disease mean?
The small intestinal tract is a remarkable organ. It has to neutralize acid from the stomach, apply digestive enzymes and emollients, absorb and conduct away the microscopic nutrients, and move its contents from one end of our body to the other. There is also the matter of housing a variety of bacteria without allowing them to access the interior of our body, immunological reactivity, hormonal activity and response, and more. Its layers act as both a barrier and gateway, plus it must have muscle strength for tone and motion. Proper function depends in part on normal thickness of all the delicate layers.

Diseases of Infiltration:
Disease can lead to an influx of inappropriate cells into the layers of the intestine. This infiltration of the bowel by abnormal cells creates thickening and puffiness, which hampers function. The thick intestine does not contract properly, which leads to food pooling and sludging. Pooling and sludging leads to the sensation of nausea and malaise. The thick intestine also cannot absorb nutrients properly, which leads to weight loss and diarrhea. Frequently there is ulceration and bleeding as the membranes become unhealthy.

Bacterial populations become altered when the nutrients available to them change in composition. In other words, what sort of bacteria live in the bowel depends on what nutrients are in abundance around them. Different nutrients promote different bacterial populations for better or worse. Abnormal nutrient absorption can lead to an overgrowth of bacteria or at least an alteration in the proportions of different populations of bacteria, creating a bad neighborhood in the bowel. Toxic bacterial products can be produced. Bacteria can overpower natural barriers, allowing them to crawl up the pancreatic duct or bile duct where they create inflammation in organs that are normally sterile (pancreas and liver).

Fixing it Depends on Knowing the Nature of the Infiltration
There are two common diseases that involve infiltration, intestinal lymphoma and inflammatory bowel disease (IBD). Both diseases involve lymphocytes infiltrating the delicate bowel. In lymphoma, these are malignant cancerous lymphocytes. In IBD, they are active lymphocytes reacting inappropriately to an immunological trigger (such as a food or bacterial waste product). Biopsy is necessary to distinguish these two diseases and distinguishing between the two conditions, allowing for the most effective treatment.

Treating Lymphoma
There are two forms of lymphoma, one associated with a rapid and sustained response to therapy with remissions of one year or longer being common, and the other type being nearly untreatable. Biopsy will determine which type a cat has. Confirmation of lymphoma also allows for a more tailored protocol so as to maximize the quality of remission.

Treating Inflammatory Bowel Disease
IBD is an immune-mediated disease and treatment centers on suppressing the inappropriate immunological response so that the bowel can recover. Special diets may be employed to minimize inappropriate reactions to food in long-term management. It is theoretically possible, eventually, to recover from this disease completely, though most patients need long-term medications to control the inflammation.

The possibly good news here is that because both conditions involve lymphocyte infiltration, there is a great deal of overlap in therapy, so it is possible to make up a treatment plan that will cover both possibilities with a reasonable chance of success. This is not optimal but provides a route to less expensive therapy.

Diagnostics Start with Ultrasound
The normal diagnostic sequence involves basic examination, lab work to rule out metabolic issues, and abdominal ultrasound followed by either endoscopy to obtain intestinal biopsies or exploratory surgery to obtain biopsies. A great deal of information can be obtained by ultrasound. Ultrasound allows for evaluation of tissue not accessible during endoscopy or even surgery. Further, it may even be possible to get the diagnosis without the expense and stress of intestinal biopsy if tissue can be obtained by ultrasound guidance.

That said, there are some caveats to the use of ultrasound as the final diagnostic. For example, there is a great deal of over-lap in bowel thickness between what normal patients have, what IBD patients have, and what lymphoma patients have. Normal patients will not have abnormal layering but sick patients can have completely normal layering. More severe disruptions in layering are more typical of lymphoma, especially when they occur in separate segments, but less severe wall thickness change is not very specific.

Some diagnostic considerations with abdominal ultrasound are as follows:

  • Severe bowel layer distortion implies (but does not confirm) malignancy
  • Milder bowel layer changes could be from either IBD or lymphoma
  • If any lymph nodes are enlarges, they may be aspirated with guidance from the ultrasound. If lymphoma is found, the diagnosis is made. If the node is immunologically reactive only, this does not rule out lymphoma but implies benign disease
  • If no lymph nodes are enlarged, the liver may be aspirated. If lymphoma is found, the diagnosis is made. If lymphoma is not found in the liver, it is not ruled out in the intestines
  • Growths or masses may be discovered that are best managed with surgical removal
  • Disease in other organs may be discovered

If ultrasound findings are not specific and the diagnosis remains ambiguous, in a perfect world referral for endoscopy follows, biopsy samples are taken, and a tailored therapy can initiate, or at least informed decisions can be made. Not every patient is stable for anesthesia, however, and not every owner is financially able to pursue a specialized procedure.

Because there is a great deal of overlap between the treatment for IBD and the treatment for lymphoma, a therapy plan can be designed that covers both possibilities reasonably well. Typically this involves corticosteroids, immunosuppressive medications, special diet, probiotics and nutritional supplements. Response to medication is generally rapid (within a week or two) for IBD, and a common lymphoma statistic is that 75% will achieve remission within three weeks regardless or protocol. Longer remissions can be obtained with more tailored protocols.

Giardia in Dogs


Giardia is a protozoan parasite found all over the world. It infects humans, many domestic animals and birds. Giardia lives in the intestinal tract and infection may be asymptomatic or can result in gastrointestinal symptoms.

Giardia infections (called Giardiasis) show no gender or breed predilection but are most common in young animals and in animals under close confinement, such as those in kennels, animal shelters and pet stores.

Most cases of Giardia infection in humans arise from person-to-person contact or from contaminated water, but animals do harbor strains of Giardia that are infectious to humans and animal-to-human transmission theoretically is possible.

What to Watch For

  • Diarrhea

  • Vomiting

  • Weight Loss

  • Flatulence (excessive gas)


    Veterinary care should include diagnostic tests and subsequent recommendations. Diagnostic tests are needed to recognize Giardiasis and exclude other diseases. Tests may include:

  • Direct fecal smears to look for two different stages of Giardia organisms called “cysts” or “trophozoites.” A positive direct smear results in a conclusive diagnosis of Giardiasis, but direct fecal smears may be negative in infected animals.

  • A zinc sulfate concentration test to identify Giardia cysts.

  • An enzyme-linked immunosorbent assay (ELISA) test to identify Giardia antigens in the stool.

  • Direct immunofluorescence test to identify Giardia cysts in feces.

  • Collection of samples from the duodenum (first part of the small intestine) during endoscopy and examination for Giardia trophozoites.


    Treatment for pets with Giardia infection may include one or more of the following drugs:

  • Metronidazole

  • Fenbendazole

  • A combination of praziquantel, pyrantel and febantel

    Home Care and Prevention

    Administer as directed all medications prescribed by your veterinarian. All of the prescribed medication should be given to ensure elimination of the infection. A high-fiber diet may improve stool consistency in pets with diarrhea associated with Giardia infection.

    Decontamination of the environment is an important part of preventing infections. In multiple-dog households and in situations in which animals are under close confinement (e.g. kennels, animal shelters, pet stores), proper sanitation is crucial to prevent cross-contamination from one animal to another. All fecal material must be removed from cages, runs and yards. Kennels must be cleaned with appropriate disinfectants and totally dried before allowing pets access to them.

    All animals should be treated with appropriate medication before being introduced into a multiple-animal environment.

    Bathing animals before introducing them into an uncontaminated environment allows for removal of feces and infective cysts from the hair coat.

    Pet owners should remove feces from the yard, avoid allowing their dog to drink from streams and lakes, and regularly bath the animal to remove any feces from the hair coat.

    Information In-Depth

    The protozoan parasite Giardia occurs in two forms. The active (motile) form that lives and multiplies in the intestinal tract is called a “trophozoite.” It can be recognized under the microscope by its characteristic appearance, which looks somewhat like a monkey face with two eyes and a nose. The trophozoite only lives in the intestine and cannot survive in the environment for any significant length of time. The other form is called a "cyst" and is the infective form of the parasite. Each cyst contains two completely formed trophozoites inside of it. Cysts can remain viable in the environment for many months and can cause infection if conditions are cool and moist.

    Dogs are infected by ingesting cysts in the environment. Most infections arise from contaminated water, such as puddles, streams, lakes, shallow wells and water contaminated by feces.

    Giardia causes disease by damaging the small intestine, which leads to maldigesion (inability to break down nutrients properly) and malabsorption (inability to properly absorb digested nutrients). Giardia also increased intestinal motility, thus decreasing the amount of time the intestine can digest and absorb nutrients. Increased intestinal motility may be manifested by flatulence (excessive gas production) and diarrhea.

    The most common symptom of Giardia infection is diarrhea but there are many other causes of diarrhea. Some examples include:

  • Dietary disturbance: sudden changes in diet, overfeeding, dietary indiscretion (like getting into the garbage and eating too many table scraps)

  • Drugs: aspirin and similar non-steroidal anti-inflammatory drugs such as ibuprofen; many antibiotics; anti-cancer drugs; heavy metals (lead, arsenic); insecticides

  • Other parasites including worms (hookworms, roundworms, whipworms, tapeworms), and protozoa (coccidian, Entamoeba, Trichomonas, Balantidium)

  • Viruses: parvovirus, coronavirus

  • Bacteria: Salmonella, Campylobacter, Clostridium, E.coli

  • Obstruction of the intestinal tract by foreign bodies

  • Tumors of the intestinal tract

  • Mechanical obstruction of the intestinal tract caused by volvulus (twisting of the intestine) or intussusception (telescoping of the intestine on itself)

  • Metabolic disorders such as kidney failure, liver failure and hypoadrenocorticism

    Diagnosis In-Depth

    Diagnostic tests are needed to identify giardiasis and exclude other diseases. Tests may include:

  • A complete medical history and a thorough physical examination. Specific diagnostic tests will be needed for your veterinarian to diagnose giardiasis in your pet

  • Direct examination of a fecal smear under the microscope. The trophozoites are more likely to be seen in diarrhea and the parasite can be recognized by its rapid forward motion. Cysts are more likely to be found in semi-formed feces. It takes considerable expertise to be able to recognize cysts.

  • Fecal enzyme-linked immunosorbent assay (ELISA) test to detect substances given off by the trophozoites in feces. Your veterinarian may be able to perform this test in the office or may send a fecal sample to a laboratory that conducts this test.

  • Zinc sulfate concentration test. A fecal sample is mixed with a zinc sulfate solution and, after a few minutes of processing, Giardia cysts (if present) will float to the top of the solution where they can be collected and identified under the microscope. If this test is performed on three separate fecal samples from the same dog, it will detect Giardia more than 96 percent of the time in infected animals.

    Treatment In-Depth

    Several drugs have been used to treat Giardia infections in pets. Anti-parasitic drugs are the most important part of treatment, but additional measures such as adding fiber to the diet can improve stool consistency and hasten your pet’s recovery. Specific treatments include:

  • Metronidazole is an antibiotic that has been widely used to treat Giardia in dogs as well as in people. This drug has reasonable efficacy against Giardia and has the added advantage of being effective against other parasitic protozoa and some bacteria that may also have contributed to the diarrhea. Adverse effects on the nervous system have occurred with high doses.

  • Fenbendazole is a de-worming medication that kills common parasitic worms such as hookworms, roundworms and whipworms. When given at the usual dosage, fenbendazole is also very effective against Giardia. Fenbendazole is very safe.

  • The combination of praziquantel, pyrantel and febantel is another de-worming medication used against parasitic worms, such as hookworms, roundworms, whipworms and tapeworms. Recent studies show that it also is effective against Giardia. Treatment only has to be given for three consecutive days. The drug, however, is somewhat expensive.


    Optimal treatment for your pet requires a combination of home and professional veterinary care. Administer any medications prescribed by your veterinarian and notify your veterinarian if you are experiencing problems treating your pet.


    Follow dietary changes recommended by your veterinarian such as increasing the fiber content of the diet. Follow specific recommendations for controlling the disease such as decontaminating the environment, keeping your pet’s hair coat clean and avoiding reinfection by preventing your pet from drinking from puddles, lakes, streams and other sources of stagnant water.


    After finishing treatment, submit a fresh fecal sample to your veterinarian to confirm effective treatment. If, after several days of treatment, no improvement is noted, return your pet to your veterinarian for re-evaluation.