Inflammatory Bowel Disease vs. Irritable Bowel Syndrome: Which is affecting my cat?

INFLAMMATORY BOWEL DISEASE

What is Inflammatory Bowel Disease and what causes it?

Inflammatory Bowel Disease (IBD) is a chronic disease of the intestinal tract. In fact, IBD is not a single disease, but several conditions that result in the accumulation of inflammatory cells in the intestinal tract. These inflammatory cells are normal cells that occur in the body, but problems within the body cause these cells to congregate in the stomach or intestinal tract, causing thickening of the linings of these organs and decreasing the organs' ability to perform their normal activities: digesting food and absorbing nutrients.The thickened lining also decreases the body's ability to protect itself from harmful invaders like bacteria and viruses. The lining of the intestinal tract normally functions similarly to the skin in providing a protective layer between harmful infections and the rest of the body's vulnerable cells.

Normal intestinal anatomy - the villi absorb nutrients and pass them into the bloodstream for distribution throughout the body

Most of the time, the primary cause of IBD is unknown or "idiopathic", but chronic inflammation may be caused by diet, environment, parasite infection, immune health or the relationship between the body's immune system and the bacteria that inhabit the digestive tract. While food allergy may not be a primary cause of  IBD, it may be a contributing factor to the severity of the disease.

What are the signs of Inflammatory Bowel Disease?

Inflammatory bowel disease is generally a problem found in cats of middle age and older, but can affect cats of any age. Most affected cats have a history of recurrent or chronic vomiting and/or diarrhea.  During periods of vomiting or diarrhea, the cat may lose weight but is generally normal in other ways. As a rule, most affected cats eat well (or even have an increased appetite) and appear normal, though some cats may have decreased appetite.

Depending on which part of the digestive tract is affected, the cat may be more likely to vomit (stomach, duodenum) or have diarrhea or bloody stools (colon). Mucousy stools may also be a sign of IBD. However, a cat that vomits due to IBD may vomit after every meal, or only once or twice a month. Vomiting may be intermittent or cyclical. The cat may be more prone to hairballs that disrupt the digestive tract - either vomiting hairballs frequently, or by having his digestive tract become obstructed by a hairball. If the whole digestive tract is affected, the symptoms may not necessarily directly correspond to the areas most affected.

How is IBD diagnosed?

Ultrasound examination of a cat

Diagnosis of IBD can be complex, because the common signs (vomiting and/or diarrhea) are symptoms that can be associated with many diseases. Because IBD often is idiopathic in nature, your veterinarian will recommend diagnostics that will rule out more specific diseases, first, such as parasites, viral or bacterial infections, metabolic diseases and cancer. This may involve various blood tests, a stool examination and abdominal radiographs or ultrasound examination. The veterinarian may palpate or feel thickened intestines during the physical exam, or may see evidence of intestinal thickening on x-ray or ultrasound studies.

For most cats with IBD, bloodwork chemistries may be normal. If the liver and pancreas are involved (triaditis), then elevations of pancreatic or liver enzymes would be expected. In cases where the cat is having bouts of severe vomiting or diarrhea, electrolyte imbalances would be a common finding. Additionally, long-standing IBD may result in "protein-losing enteropathy". In a normal cat, a small amount of protein leaks into the intestine as nutrients are absorbed into the bloodstream. These proteins are normally digested in the intestine and then reabsorbed. When the intestinal tract is damaged, as in IBD, more protein leaks out than the body is able to reabsorb.

The only way to definitively diagnose IBD is to collect surgical biopsies of the digestive tract and submit them for pathologist review. The types of cells seen by the pathologist will determine whether IBD is present, and categorize whether the IBD is lymphocytic-plasmacytic (the most common), eosinophilic, neutrophilic or granulomatous in nature. 

Here is what the lining of a normal intestine looks like under the microscope. The areas within the boxes are what we are looking at, below.

The images towards the left show normal intestinal anatomy, while the images to the right show progressively more severe Inflammatory Bowel Disease (human). There is a decrease in the size and surface area of the villi, the thickness of the intestinal lining , and a general degeneration of intestinal anatomy.  Loss of structure = loss of function

Surgical biopsies can be collected via endoscopy or via exploratory surgery. Endoscopic biopsies are less invasive, but are limited because only the upper end of the GI tract can be sampled, and only superficial samples can be collected. Surgical exploration to collect biopsy samples allows full-thickness biopsies of multiple sites throughout the digestive tract to be collected. Additionally, since many cats that have IBD may also have pancreatitis or hepatitis (inflammation in the pancreas or liver), samples of these organs and abdominal lymph nodes can also be collected to ensure that there are no additional complicating factors to the disease.

The first method is a biopsy of the affected part of the stomach or intestine.  The preferred technique to to use a flexible endoscope which allows access to the lining of the stomach, small intestine, and colon.  If the site of inflammation involves any of these locations, a confirmed diagnosis is achieved.  Sometimes, the small intestine may be difficult to enter because of the cat’s small size; in these cases, surgical biopsy may be needed.  Fortunately, this is rarely necessary. The second method of diagnosis is a therapeutic trial involving administration of particular drugs, along with certain dietary changes.  Since not all cats respond to the same drugs, the trial may involve a series of a number of drugs and may take several weeks.  Also, different diets may be tried, depending on which part of the bowel appears most involved.  These diets include hypoallergenic, low residue, or high fiber foods.  The cat is monitored during the therapeutic trial for a decrease in clinical signs and, in some cases, weight gain.

Is IBD treatable?

Treatment for IBD is focused on controlling symptoms such as vomiting and diarrhea and promoting appetite and weight gain. Any complicating factors such as pancreatitis, parasite infection or other diseases should be treated accordingly. Treatment may involve a special diet, anti-vomiting or anti-diarrheal medications, steroids, pre- or pro-biotics, dewormers, omega-3 fatty acids, and B12 supplementation.

What is the prognosis?

Once the appropriate drugs or diet are determined, many cats are maintained on these for life, although dosages of the drugs may eventually be decreased.  Occasionally, a cat will be able to stop drug therapy at some point. Most cats do well for many years; others require alterations in therapy every few months.  Unfortunately, a few cats will ultimately become totally resistant to treatment.

There is a correlation between IBD and gastrointestinal lymphoma in cats. It is not completely clear whether IBD causes or progresses to lymphoma (the most common type of cancer in cats) over time, or whether the same problems that lead to IBD also cause GI lymphoma. Either way, untreated IBD in cats can cause malnutrition and eventual gastrointestinal ulceration and possible perforation of the bowel. Perforation of the bowel allows partially digested food and intestinal bacteria to leak into the abdomen causing severe systemic infection, sepsis and death.

IBD vs. IBS

Irritable Bowel Syndrome (IBS) is not the same as Inflammatory Bowel Disease (IBD). Irritable bowel syndrome is a psychosomatic response that causes hypermotility in the intestinal tract (things move through too quickly). The most common reason for this to happen is excessive stress or anxiety - a trip to the veterinary hospital, the addition of a new cat or new baby to the household, etc. A biopsy of the intestinal tract would look normal, because the problem is not with the intestinal tract itself, but with the nerve signals sent to the intestine that tell it what to do. Treatment of chronic irritable bowel syndrome is aimed at increasing fiber in the diet and controlling the cat's anxiety through environmental management and behavioral therapy. One-time bouts of IBS resulting from travel, visits to the veterinary hospital or other planned events can be averted by acclimating the cat to the carrier, using calming products, such as Feliway or anti-anxiety medications prior to travel or veterinary visits, or by choosing a veterinary office that is a certified Cat Friendly Practice. These hospitals generally have staff experienced with handling stressed cats, have separate waiting rooms, cages and exam rooms for cats and dogs, and may be better equipped to soothe your anxious kitty, preventing the onset of an IBS episode.

Additional Resources
Merck Veterinary Manual: Disease Profile: Inflammatory Bowel Disease 

All Feline Hospital: Inflammatory Bowel Disease 

Cornell Feline Health Center: Inflammatory Bowel Disease

WebMD: Inflammatory Bowel Disease

Wild Rose Cat Clinic Case Study: Tigger, and is it IBD or Lymphoma?

World Journal of Gastroenterology: Inflammatory Bowel Disease in the Dog: Similarities and Differences with Humans