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Tom Keane, a lawyer in New York City, came home from work to
what had become a familiar sight: two or three small
puddles of vomit, in various rooms of his apartment.
Previous visits to the veterinarian had shown Tom’s cat,
Boo, to be in relatively good health. Blood tests and
x-rays had revealed no abnormalities. Boo was deemed “a
vomiter” by the veterinarian, and Tom had learned to
live with Boo’s thrice weekly messes. In the past few
months, however, Boo’s problem had gradually grown more
severe, and his thrice weekly episodes had now become
thrice daily. “I guess I had grown used to it”, said
Tom, “but now it’s really gotten out of hand.”
On physical examination, Boo, a 10 ½
pound 8 year-old orange tabby, was bright and alert, and
no abnormalities were detected. Blood tests and
urinalysis were performed and were normal, indicating
that a systemic illness, such as hyperthyroidism or
chronic renal failure, was not responsible for Boo’s
clinical signs, and that a primary gastrointestinal
disorder was the likely cause. “Tom”, I said, “I have a
sneaking suspicion that Boo has inflammatory bowel
disease.”
Inflammatory Bowel Disease (IBD) is an uncontrolled or
excessive gastrointestinal inflammatory response,
resulting in the infiltration of inflammatory cells into
various segments of the gastrointestinal tract. There is
no age, gender, or breed predisposition for feline IBD,
however, most cats tend to be middle aged or older.
Inflammatory Bowel Disease is often mistakenly called
Irritable Bowel Syndrome.
“The most common symptom of feline IBD is weight loss.
This may or may not be accompanied by a decreased
appetite, vomiting, or diarrhea”, says Dr. Anne
Sinclair, a board-certified feline specialist and owner
of Cat Sense Feline Hospital and Boarding in Bel Air,
Maryland. In Boo’s case, vomiting was his only clinical
signs. He still had a good appetite, had no diarrhea,
and had managed to maintain his weight.
“In most cats, physical examination tends to be normal”,
says Dr. Sinclair. “The most common finding on
examination is weight loss. Occasionally, thickened or
fluid-filled intestines are evident when the abdomen is
examined.”
Feline IBD is a diagnosis of exclusion. In other words,
there are many disorders that can cause gastrointestinal
inflammation, and these should be ruled out before
honing in on a diagnosis of IBD. Examples of other
disorders to consider include intestinal parasites,
viral infections such as feline leukemia or feline
immunodeficiency virus, food intolerance, food allergy,
gastrointestinal cancer, and metabolic disorders such as
hyperthyroidism.
In cases of IBD, routine laboratory tests tend to be
normal. Protein levels in the bloodstream may be either
high or low. Increased liver enzymes are occasionally
reported in cases of feline IBD and may be important
given the recent studies that reveal that many cats with
IBD have concurrent inflammation of the liver and bile
ducts (cholangiohepatitis) and/or pancreatitis. In one
published case series, a low cholesterol level was the
most common biochemical abnormality reported.
In any workup for gastrointestinal disease, x-rays and
ultrasound are important diagnostic tools to rule out a
GI obstruction or an abdominal mass. Radiographs,
however, are ineffective for diagnosing IBD. Increased
intestinal wall thickness and enlarged intestinal lymph
nodes may be visible on ultrasound in suspected cases of
IBD, however, these finding are suggestive, not
diagnostic, of IBD. Ultimately, a definitive diagnosis
requires obtaining biopsy specimens from the GI tract.
Biopsies of the GI tract can be obtained either via
endoscopy or exploratory surgery. Endoscopy is a
procedure in which a long, flexible snake-like probe
(the endoscope) enters the GI tract through the cat’s
mouth (“upper GI endoscopy”) or anus (“lower GI
endoscopy”), in order to visualize the internal lining
of the GI tract and obtain biopsy specimens.
Endoscopy is the preferred method of obtaining biopsies,
however, if concurrent abnormalities are present, such
as markedly increased liver enzymes on the chemistry
profile, or enlarged lymph nodes, or an abnormal liver
or pancreas is seen on ultrasound, abdominal exploratory
surgery may be warranted so that biopsy specimens of
these organs can be obtained in addition to the biopsies
of the gastrointestinal tract. Endoscopy offers
advantages over surgery in that it is less invasive,
allows for direct examination of the mucosal surfaces
(innermost lining) of the GI tract, and may guide the
endoscopist to a good location for obtaining biopsy
specimens if irregularities or ulcerations of the
mucosal surface are detected. The limitations of
endoscopy are that the biopsy specimens that are
obtained by this method consist only of the mucosal
lining rather than a full-thickness biopsy of the
intestinal tract, occasionally resulting in a
misdiagnosis if the disease process primarily involves a
deeper layer of the intestinal wall. Another limitation
is that during upper GI endoscopy, the endoscope can
only reach the stomach and the duodenum (the first part
of the small intestine). The jejunum (the next part) and
the ileum (the final part) cannot be reached with an
endoscope. Both procedures – endoscopy and abdominal
exploratory surgery – require general anesthesia.
The typical finding on biopsy specimens of the GI tract
is an increased number of inflammatory cells, as well as
an altered structure of the intestinal lining. Depending
on the predominant cell type seen in the biopsy
specimens and the section of the GI tract that is
affected, the condition is given a name. For example, if
lymphocytes and plasma cells are the primary
inflammatory cell detected, the inflammation is called “lymphoplasmacytic”.
If eosinophils (a type of white blood cell often
indicating allergic or parasitic disease) are the
predominant cell type, the term “eosinophilic” is used.
The part of the gastrointestinal tract that is affected
is also included in the naming. For example, if the
small intestine is affected, the term “enteritis” is
used; if the stomach is involved, the term “gastritis”
is used (see “Glossary, Sidebar 1). Finally, the
pathologist is likely to subjectively describe the
degree of severity of the inflammatory change. For
example, a pathology report might read:
“lymphoplasmacytic gastritis, mild; lymphoplasmacytic
enteritis, severe”, indicating that both the stomach and
small intestine are infiltrated with lymphocytes and
plasma cells, with the small intestine being the more
severely affected site. Lymphoplasmacytic is the most
prevalent form of feline IBD. Eosinophilic is the second
most common form. Other forms (suppurative,
granulomatous) have been described, but are much less
common. Boo’s endoscopy did yield a diagnosis of IBD,
specifically, severe lymphoplasmacytic enteritis.
A dilemma for pathologists is distinguishing severe
lymphoplasmacytic inflammation from early stage
lymphosarcoma, a type of cancer. In fact, it has been
speculated that severe forms of IBD can transform into
lymphosarcoma over time.
“Treatment of feline IBD can be challenging. The goal of
treatment is to identify and remove the cause of the
inflammation if possible, and to suppress the immune
response. This is usually accomplished through the use
of special diets and immunosuppressive drugs”, says Dr.
Blair Hillary Ebert, a veterinary practitioner from Long
Island, NY who limits her practice to cats.
“No one diet is suitable for cats with IBD”, says Dr.
Ebert. “Some cats respond to a particular diet while
others may show a lesser response, or no response at
all.” Highly digestible diets may be beneficial. A
hypoallergenic diet may produce significant improvement
in some cats with IBD. A hypoallergenic diet is a diet
that contains a protein source that the cat has never
been exposed to before. There are numerous commercially
manufactured hypoallergenic diets available through most
veterinarians that contain novel protein sources such as
rabbit, venison, and duck. Hill’s Pet Nutrition (Topeka,
Kansas) has marketed a hypoallergenic diet (Hill’s®
Prescription Diet® Feline z/d™) that contains protein
that has been hydrolyzed into fragments that are too
small to be detected by the immune system, obviating the
need to specifically identify a suitable novel protein.
“Hypoallergenic diets alone, however, are inadequate at
inducing long-lasting remission in cats with IBD”, notes
Dr. Ebert. If a cat responds completely to a novel
protein diet alone, the likely diagnosis is food
sensitivity or allergic reaction to food rather than IBD.
Corticosteroids are the most commonly prescribed
immunosuppressive drugs for the treatment of IBD.
Typically, oral prednisone is given for at least 2 to 4
weeks. If clinical signs resolve, the dosage of
prednisone is slowly tapered until the lowest effective
dose is reached. In cases of severe inflammation in
which a dietary change and prednisone are ineffective,
other immunosuppressive drugs can be added. If cats with
severe IBD do not respond to treatment, the veterinarian
may need to reassess the diagnosis and consider that the
severe IBD may in fact be lymphosarcoma.
Although IBD isn’t curable, the prognosis is good for
adequate control of the disease. In one case series, 79%
of cats with IBD showed a positive response to treatment
with diet and prednisone. Fortunately for Tom, Boo
responded dramatically to prednisone and a change in
diet, with his vomiting episodes decreasing to
approximately one episode a month. “I certainly don’t
miss the sound of Boo vomiting in the middle of the
night”, says Tom, “and Boo has never looked and felt so
good.”
Glossary
Gastritis – inflammation of the stomach
Enteritis – inflammation of the small intestine
Colitis – inflammation of the colon (large
intestine)
The above terms can be combined to describe situations
in which concurrent inflammation of different parts of
the GI system are present, for example:
Gastroenteritis – inflammation of the stomach and
small intestine
Enterocolitis – inflammation of the small
intestine and colon
Gastroenterocolitis – inflammation of the
stomach, small intestine, and colon
Updated
7/26/06 |
