Evaluation of Gastrointestinal Disease
Dogs’ and Cats’ Most Common Medical Problems
Gastrointestinal diseases are the most common internal medicine problems in dogs and cats. Skin diseases may be more frequent in warm climates where external parasites are common. Small animals will predictably have one or more episodes marked by vomiting and diarrhea sometime in their lifetime. The most common cause is consumption of different food. Often veterinarians are not consulted because owners recognize that these problem are not usually serious and are likely to disappear without treatment.
Cause of Gastrointestinal Disease
A History Common for Gastrointestinal Diseases
The
acquisition of a puppy or kitten requires careful evaluation for health and
appearance. The care a pet receives the first months of life decides its
health. Often that care dictates health for the rest of its life.
Prospective owners should examine an animal's behavior and general condition
to evaluate that care. This is important for avoiding problems, many of
which start early. Animals raised under "farm" conditions are more likely to
have intestinal parasites. Factory farm operations also feed puppies and
kittens inexpensive poor quality commercial foods from the time they can eat
solid food. Physical condition of breeding animals is often poor after
raising a litter. Puppies and kittens from these operations are often so
unthrifty, underweight, flea-infested, or fearful-of-people that they should
not be purchased. Acquiring such animals is usually the beginning of
problems. Dogs and cats reared under farm operation conditions frequently go
on to suffer a lifetime of gastrointestinal problems. They often must be fed
special diets indefinitely. When fed commercial pet foods, including dog
biscuits, many have severe bouts of diarrhea with or without vomiting. Many
of these animals are examples of what happens when pet foods are fed before
they can develop oral tolerance. This practice sets the stage for lifelong
problems. Most pets do not have major problems with diarrhea beginning at a
young age. They do commonly have occasional bouts of diarrhea. Some of these
animals go on to develop recurring or continuous problems. The basis for
getting these problems is similar to that in animals having the problem from
a very early age (see section on adaptation to the diet).
Chronic Dietary Allergies
Pets
with chronic gastrointestinal disease (and not having cancer) have clinical
signs of disease that usually begin with a single episode from which the
animal recovers. Recurrence follows and the relapses cycle at intervals of
days to weeks. Without any effective management, clinical signs eventually
become continuous. What happens during the initial episode to cause the
animal to develop a recurring problem that if untreated eventually becomes
continuous?
Initial Insult to The Gastrointestinal Tract
A
variety of causes result in the initial episode. Changes in diet, infectious
diseases, intestinal parasites, and toxins or poisons are the most common
causes for initial episodes. These insults damage mucosal surfaces so that
mucosal cells are lost. The mucosa’s protective barrier is lost. As a result
fluid and electrolytes escape into the gastrointestinal tract and are lost
in diarrhea and vomitus. More important, the damaged barrier can no longer
protect against entry by intact foods. The mucosa is now permeable to entry
of any intestinal contents.
Activation of Immune Responses
Except for products of completely digested food, the
immune system reacts to all absorbed intestinal contents as foreign. Immune
cells produce antibodies against foreign material and an allergic response
appears whenever any such material subsequently enters the gastrointestinal
tract. Foreign material can also stimulate immunocytes so they react with an
allergic response after any subsequent exposure. By that, either or both
antibodies and immune cells can produce allergic responses.
Allergy Causes
An
allergy can develop to almost anything consumed. The most common foods
involved are cereals, especially wheat, barley, and oats, all of which
contain gluten; meats; and sometimes eggs. Of these foods it is surprising
that dogs and to some extent cats develop allergies to meat. It is unknown
why so many dogs develop meat allergies. Some even react to the very small
amounts of meat powder in pet vitamin and mineral chewable tablets. Some
dogs show allergic reactions to meat powder in heart worm prevention tablets
given daily or monthly. Animals develop no allergies to any dietary fat.
Fats and carbohydrates can cause diarrhea but for reasons other than
allergies. Commercial pet foods contain nonnutrient ingredients to which
allergies can develop. For example, some dogs with chronic diarrhea are
treated by feeding lamb and rice prepared by the owner. The dogs respond
well and become completely normal. Some owners find it inconvenient to
prepare this diet indefinitely and change to a commercially prepared lamb
and rice dog food. Changing to the commercial food proves to be unacceptable
for some dogs, however, because the diarrhea returns.
Allergy to Gluten in Cereals
Gluten-induced enteropathy is the best understood of all food allergies.
This allergy is to proteins in wheat, barley, oat, and rye cereals. Studies
in people show the problem can be inherited. There is also evidence from
animal studies that the problem develops during an episode of
gastrointestinal disease initiated by another cause. Anything that increases
mucosal permeability to permit absorption of intact material can cause an
animal to develop gluten-induced enteropathy when gluten-containing cereals
are present. Some animals have an inherited tendency for their mucosa to be
more permeable to the absorption of intact substances. Most, however, have
the acquired form that develops when another disease increases mucosal
permeability. The disease can be acquired without showing any clinical signs
for months or years. People with gluten-induced enteropathy often have no
symptoms until the disease worsens because of an insult such as surgery,
diarrhea caused by infectious agents or other causes, and even by
antibiotics that disrupt the population of normal intestinal bacteria. Dogs
may be similar in having the disease but not showing any signs until
intestinal damage worsens. Increasing dietary gluten worsens the mucosal
damage. Signs may not appear until more gluten is consumed. Thus, it is not
unusual to have intestinal damage yet no signs are reported. (Secondary
signs such as borborygmus, flatulence, halitosis, etc. may be evident but
are ignored by owners.) Gluten-induced enteropathy is similar to other
allergies caused by 1)bacterial overgrowth of the small intestine,
2)parasites such as Giardia, and 3)other food allergies. The allergies are
similar because the memory for these allergies is in T-lymphocytes. Tissue
damage in gluten-induced enteropathy does not begin in mucosal cells but in
small blood vessels of the lamina propria. The changes resemble those caused
by temporary circulatory impairment of the intestine. Mucosal cells are
damaged secondary to the circulatory changes, and these cells cannot heal
until normal circulation returns. With severe damage the mucosa may not
recover. In others, dietary treatment must continue for months or years
before remission is seen. Commercial pet foods contain some form of gluten,
and even small amounts can prevent recovering. Dogs with chronic
gastrointestinal disease should be fed gluten-free diets. With time,
affected animals can lose an allergy to gluten and recover oral tolerance
for this food. Dogs fed gluten-free diets lose allergy to glutens and can
ultimately be fed them.
Infectious Causes
Acute or
chronic diarrhea has many causes other than diet. They are less common than
dietary causes. Causes include infectious diseases such as canine distemper,
feline distemper, canine parvovirus infection, chronic fungal infection,
Salmon poisoning, and occasionally infection caused by bacteria such as Salmonella, Campylobacter, or a form of Clostridia. Other
bacteria such as some Escherichia coli may be responsible but no
studies have been done to verify that. Most owners vaccinate dogs and cats
for protection against the viral infections, making infection by these
organisms unusual. The bacterial infections are uncommon and develop as a
problem secondary to some more important disease. For example, it is
difficult to infect a dog or cat with Salmonella bacteria unless
disease debilitates the animal. Causes of debilitating disease include
chronic inflammatory bowel disease, very poor nutrition, intestinal
parasites, distemper, or a cancer such as lymphoma. Other bacteria such as Campylobacter can populate the intestines and either cause no
clinical signs or diarrhea and vomiting. Thus, finding Campylobacter on fecal cultures may be unimportant. Clostridia normally live in the intestines and cause no problems. Some antibiotics can
disrupt the normal microflora and cause some antibiotic-resistant and
toxin-producing forms of Clostridia to multiply. Bacterial toxin
production increases and destroys intestinal mucosa cells. Normal numbers of
bacteria do no harm; mucosal damage happens only with disruption of the
intestine’s normal environment. Some animals can be infected with other
forms of Clostridia by consuming food or other material containing Clostridium perfringens.
Evaluation of Response to Antibiotics
Acute
(and sometimes chronic) diarrhea is often treated with antibiotics. Recovery
within 24 hours makes it appear that antibiotics were of benefit. Recovery
without a need for antibiotics is usual, however. Scientific controlled
studies in humans with "traveler's diarrhea," where infection is usually the
cause, show that treatment including antibiotics is no more effective than
treatment without antibiotics. Also some cases of diarrhea caused by
noninfectious problems, such as a deficiency of digestive enzymes, respond
to treatment with antibiotics. Thus, it is not possible to blame infection
as the cause of diarrhea just because the animal responds to antibiotics.
Also, when allergies develop against intestinal contents, allergies can be
to the content's bacteria. Then, using antibiotics to reduce bacterial
numbers improves clinical signs.
Intestinal Parasites
Intestinal parasites are not a common cause for persistent diarrhea and
vomiting. An exception is for puppies and kittens bred and raised in kennels
with chronic parasitic problems. Parasites more commonly causing clinical
signs include roundworms, hookworms, whipworms, giardia, and coccidea.
Tapeworms are common parasites that do not cause clinical signs in dogs or
cats. It is not difficult to identify intestinal parasites and treatment is
usually effective.
Chemicals
Ingestion of man-made chemicals, naturally occurring chemicals found in many
plants, and chemicals produced by some microorganisms can cause
gastrointestinal upsets. These toxicities represent few cases of diarrhea
and vomiting in dogs and cats.
Signs of adverse reaction to foods―food intolerance
Vomiting and diarrhea are two of the most common clinical signs of gastrointestinal disease. Signs other than vomiting and diarrhea signal gastrointestinal problems and often follow a recurring pattern. Many dogs and cats have occasional diarrhea such as once a week or once a month. Often owners believe that the cause is food so a different brand is fed. A change often appears to help but later it doesn't seem to make much difference. That makes it seem that food intolerance is not responsible. It possible to know if a pet reacts adversely to commercial pet foods or any other food it eats. Vomiting and/or diarrhea within 24 hours after eating is often thought to be an adverse food reaction that could very well be an allergy. Dogs and to some extent cats may show little or no evidence of these two signs but show other signs that are sometimes difficult to associate with the diet. Patterns of signs such as vomiting and diarrhea are learned from accurate and complete histories. Understanding medical problems also requires a knowledge of secondary signs. Clinical signs identify food intolerance and are necessary for monitoring response to management.
Evaluating Signs of Gastrointestinal Disease
Diarrhea
Diarrhea
is the most common manifestation of adverse food reactions. Diarrhea is a
change in one or more characteristics of bowel movements. One change is from
formed to fluid or loose feces. The second change is increased frequency of
bowel movements. Many believe that these changes define all cases of
diarrhea. A third less obvious change defining diarrhea is increased fecal
volume, however. Increase volume due to water results in loose and watery
feces. Volume increases can also be due to dietary fiber or nondigestible
matter. Large volume feces having normal water content are formed, making it
appear that bowel movements are normal. Diarrhea characterized by large
volume formed feces is a major problem in many dogs consuming commercial dog
foods. These diets are high in fiber and nondigestible matter that pass
through the gastrointestinal tract without being degraded and absorbed. The
poor digestibility of dog food ingredients produces large volume feces. Poor
digestibility relates to pet food’s high carbohydrate content, a reflection
of their cereals. Carbohydrates are the major source of energy in dog foods.
Dietary fat also satisfies energy requirements. High-caloric-density dog
foods with lower cereal and greater fat levels produce smaller-volume feces.
Some dry foods have a fat content of 20 to 25 percent compared to 7 to 10
percent in most dry dog foods. Large-breed dogs eating low fat diets often
produce unacceptably-large fecal volumes. Such dogs should be fed a
high-caloric-density diet. High-carbohydrate diets can produce small fecal
volumes if they contain cereals that are completely digested and absorbed.
Boiled polished rice is almost 100 percent assimilated, leaving very little
nondigested residue. Feeding boiled rice to dogs with diarrhea reduces fecal
volume. Reduction may so great that constipation is suspected because no
bowel movements are seen for several days. This new problem is corrected by
adding fiber to the diet.
Flatulence
Flatulence is a common and less obvious sign of food intolerance. Flatulent
gas results partially from swallowed air that is not eructated and passes
through the gastrointestinal tract. Little can be done to control that.
Bacterial fermentation of nondigestibles in the colon also produces gases,
such as methane, hydrogen sulfide, and carbon dioxide. Diets high in
nondigestible carbohydrates and sugars are associated with gaseousness.
Beans are the best known cause of flatulence in humans. Soybeans are an
important cause in dogs. Soybean meal is used in many dry dog foods. Spoiled
foods and high protein diets can produce odoriferous gases. Excessive
carbohydrate entering the colon, because of digestion and absorption
problems, usually results in flatulence. In dogs with no digestive and
absorptive problems, flatulence continues until feeding dry dog food stops.
Flatulence should disappear on feeding a highly digestible, low fiber diet,
of moderate protein content. Examples of diets to reduce flatulence include
cottage cheese and boiled rice, tofu and boiled rice, and poultry and boiled
rice diets.
Borborygmus
Borborygmus results from gas passing through the gastrointestinal tract,
primarily the stomach or colon. Absence of any sounds is abnormal.
Borborygmus is excessive gas sounds. Gas and fluid collections produce
sounds when gastrointestinal problems reduce gastrointestinal motility.
Where an adverse food reaction causes excess gas accumulation from either
aerophagia or colonic bacterial fermentation, borborygmus can be controlled
by changing to a different diet (controlled diet for a persistent problem
causing diarrhea).
Tenesmus
Tenesmus
is very often suspected to be a sign of constipation; it usually is a
manifestation of a problem causing diarrhea. An adverse reaction to food
often causes tenesmus as the primary sign. On closer examination variable
amounts of mucous and/or fresh blood are often found to coat small amounts
of feces. Blood in feces is common in dogs and cats. It is not a serious
sign unless the amount is great or persists. Blood in feces is rarely caused
by colonic cancer in dogs and cats. Tenesmus also increases bowel movement
frequency.
Abdominal Distention
Distention of the abdomen or bloating can be a sign of adverse reaction to
food. Intestinal accumulation of gas and fluid causes this distention. Gas
accumulates because gastrointestinal motility is impaired; any remaining
movement is unable to expel gas by eructation or flatulence. Fluid
accumulates for the same reason but also because adverse food reactions
stimulate intestinal fluid secretion. Occasionally postprandial abdominal
distention is the only sign of adverse food reaction.
Pain
Subtle
pain or abdominal discomfort is often difficult to assess. Dogs sometimes
assume a praying posture when experiencing abdominal pain. In that attitude
their front legs are flat on the floor and their rear end raised, an
appearance similar to a stretching movement. Intestinal distention by gas
causes the discomfort experienced during that behavior. Sometimes,
distention by an intestinal foreign object has the same effect.
Shivering
Unexplained shivering can be a sign of adverse food reaction. The shivering
results from discomfort produced by gastrointestinal tract spasms or
distention.
Anal Pruritus
Gastrointestinal and skin problems can cause anal pruritus. Parasitic
infestation by roundworms is one cause. Anal sac problems may be the most
common cause. Skin disease and fleas are also causes. When none of these are
problems, adverse food reaction is considered.
Hypersalivation
Hypersalivation is usually seen before vomition. It can also be seen without
vomiting. When hypersalivation is not caused by oral cavity or esophageal
problems, adverse food reaction must be considered.
Weight Loss
Unexplained weight loss or inability to gain weight is frequently caused by
gastrointestinal problems. Sometimes no other signs are seen. Adverse
reaction to one or more foods can cause weight loss.
Signs of Atopy
Food
allergy frequently causes pruritus confined to the face, head, and feet.
This type, called atopy, can be caused by inhaled allergans as well as those
in the diet. Atopy is difficult to solve and any form of management should
begin by doing what is easy and inexpensive. Laboratory testing (including
skin testing) is not very reliable or useful in solving this problem. The
most useful evaluation of atopy is by feeding a controlled hypoallergenic
diet. Owners can easily prepare this kind of diet. When signs of diarrhea
accompany atopy, it is usually easier to correct the diarrhea with a
controlled diet than the pruritus.
Using Signs of Adverse Food Reaction
When diarrhea and/or vomiting follow feeding, it can be easy to document an
adverse reaction to food. When owners do not see these signs, other signs
must be used to understand the problem. Finding signs such as flatulence,
borborygmus, tenesmus, bloating, anal pruritus, shivering, atopy or weight
loss. makes it important to confirm or eliminate adverse food reaction as
the cause. These other signs are also used to evaluate progress during
management. If all signs disappear the problem is solved. If diarrhea and
vomiting stop but one or more of the other signs persist, improvement is
noted but the problem remains. In many cases, the diet is changed but not
enough to completely control the problem. All signs must be monitored to
decide if the problem is eliminated.
Timing of Adverse Food Reaction Signs
Signs of
adverse food reactions usually appear within hours of feeding or at least by
24 hours. Relatively rapid reaction, immediate type of hypersensitivity, is
seen with allergies caused by antibodies produced against food. Examples of
this allergy include hives and urticaria. Most food allergies are not this
type but are due to immune cells that carry a memory for sensitivity to
food. The response is a cell-mediated type of hypersensitivity. The allergic
reaction with this type is delayed, signs appear up to five days after
contact with the offending food. Thus, it can be difficult to identify both
an adverse food reaction and the specific food causing it. Most people
cannot remember foods a animal ate several days earlier. With delayed
allergic reactions, it is difficult to identify foods that can be tolerated
when new foods are introduced one at a time. When a controlled diet is fed
and no clinical signs are seen, a single new food is gradually introduced.
The effects of this food is evaluated over a week to decide if it is
tolerated.
Further Evaluation of Gastrointestinal Disease Signs
Unexplained signs of gastrointestinal disease can be pursued by feeding a
controlled diet and closely monitoring an animal's clinical signs. Some
problems persist unsolved for so long that many secondary changes develop
which makes it more difficult or take longer for the problem's resolution.
It is important to understand how an animal develops intolerance to many
foods and why it may have had problems ever since it was young.
From a Single Acute to a Recurring Problem
Most
animals recover spontaneously from acute gastrointestinal upsets, with no
further problems ensuing. For others, however, an acute problem marks the
beginning of chronic problems. Most dogs with a continuing problem of
diarrhea show on-and-off signs. Diarrhea cycles with intervals of days to
weeks. At first the intervals between diarrhea are long, maybe four to six
weeks. When care and feeding practices are not changed, the intervals
shorten. Eventually diarrhea is continuous.5 After treatment
cycling patterns can still continue, but with less severity. Diagnostic test
help evaluate persistent diarrhea (or vomiting), the most common of all
gastrointestinal disorders.
Laboratory Evaluation of Gastrointestinal Problem
Many diagnostic tests can be done to find the cause or better understand persisting gastrointestinal problems. When these problems are evaluated by laboratory tests, it is important to advise pet owners that testing is likely to show normal results. Are tests really necessary then? They can in some cases give clues to a problem's cause. Sometimes they reveal important complications of gastrointestinal problems or even other unrelated problems. Normal test results rule out many problems and allows one to make conclusions by exclusion. So if owners choose to have a complete checkup, the tests are done. Usual testing includes complete blood count, blood chemistry panel, urinalysis, fecal examinations for parasites, and fecal screening tests for digestion and absorption abnormalities.
Complete Blood Count
A
complete blood count offers little useful information for evaluating most
dogs and cats with persistent diarrhea and/or vomiting. Occasionally
gastrointestinal disease results in anemia, hypoproteinemia due to loss of
excessive plasma proteins into the gut, gastrointestinal infection, and some
forms of cancer. Clues for many of these problems can be found in a complete
blood count. Mostly, this test reveals complications but not a cause for
problems. Anemia or hypoproteinemia infrequently requires specific treatment
such as whole blood or blood plasma transfusion. Abnormalities in a complete
blood count are seldom the reason for treating with antibiotics.
Blood Chemistry Panel and Urinalysis
Blood
chemistry panels are done primarily to evaluate for disease or impaired
function in the liver, kidneys, pancreas and endocrine glands. Panels are
also done to identify fluid and electrolyte imbalances. Defenses protect
against losses of excessive fluid and electrolytes. The gastrointestinal
mucosa is normally the leakiest of body surfaces through which fluids and
electrolytes can be lost. Disease damages mucosal surfaces so they are
leakier and extracellular fluids are lost with diarrhea and vomiting. Tests
evaluating for pathology in specific organs are usually normal.
Abnormalities usually seen identify complications rather than causes of
gastrointestinal disease. The complications usually resolve with successful
management of the primary problem. A urinalysis rarely helps in the
understanding of gastrointestinal diseases.
Blood Tests for Specific Feline Diseases
Tests
are done on cats with chronic gastrointestinal disease to evaluate for a few
specific infectious diseases. Blood tests are done to evaluate for infection
by viruses causing feline leukemia, feline infectious peritonitis, and
feline immunodeficiency (feline AIDS). Infection by these viruses can cause
signs of chronic gastrointestinal disease. In addition, a blood test is done
for hyperthyroidism; diarrhea and weight loss are important features of this
disease.
Fecal Examinations for Parasites
Parasites can cause persistent diarrhea, with or without vomiting.
Examination of fecal samples is reliable for parasite identification.
Testing for parasites is always done, even when no other tests are done.
Intestinal parasites that can cause diarrhea are relatively easy to
eliminate which usually results in normal feces. When found, parasites are
eliminated before other testing is done.
Fecal Examinations for Digestive Abnormalities
Small
intestinal diseases usually cause weight loss. Screening tests can help
identify them, with the easiest and most reliable tests done on fecal
specimens. Fecal smears are stained with Sudan III and examined
microscopically for fat droplets. Fecal smears from normal animals show few
if any fat droplets. Intestinal problems causing incomplete digestion and
absorption cause varying numbers of fat droplets to appear. More
sophisticated and costlier tests are available but they provide little
additional useful information.
Radiographic Studies and Ultrasound Studies
Radiographic studies are usually normal in dogs and cats having chronic
diarrhea with or without vomiting or weight loss. Radiographic studies can
be costly and difficult to interpret. Special radiographic studies such as
upper gastrointestinal or colonic studies using a contrast agent are also
usually normal and often difficult to interpret. Ultrasound offers another
means to examine the gastrointestinal system, as well as the entire abdomen.
Ultrasound is limited to showing thickening of the gastrointestinal wall and
intraabdominal masses. Few animals with chronic gastrointestinal disease
have these problems, however.
Endoscopic Studies
Endoscopic procedures are useful in finding the cause of disease in some
dogs and cats with chronic gastrointestinal problems. Besides examining the
mucosa, biopsies are taken. The procedure can be costly and carries a small
anesthetic risk. Clients should be advised what can be expected that
warrants the procedure. Expectations for useful information from
gastrointestinal endoscopy are limited. Usually, gross appearance of the
mucosa is normal. Biopsies can show one of three primary kinds of results.
First, the biopsy can appear normal which is the most common finding.
Second, the biopsy can show some form of chronic inflammation, the second
most common finding. Third, the biopsy can show cancer, with lymphoma being
the most common. Cancer of the gastrointestinal tract is not common in dogs
and cats, however. A pathologic diagnosis of chronic inflammation does not
identify causes so little is revealed on how the disease developed. Biopsies
taken early in the disease often show normal findings and only with
progression of chronic inflammation will biopsies confirm the diagnosis.
Owners of animals with chronic diarrhea are usually frustrated and
bewildered when intestinal biopsies show normal tissue. Also the diagnosis
of chronic inflammation dissatisfies owners when they are told that little
is known about the disease. In contrast, endoscopic biopsies may help
diagnose a specific disease if cancer is found. The interpretation of
biopsies taken during endoscopy is usually difficult because biopsy sample
size is small. Endoscopic biopsy instruments retrieve only small amounts of
tissue. For that reason the operator gets multiple biopsies and sometimes an
animal must undergo a second procedure to take more biopsies. Endoscopic
biopsies are limited to identifying disease found in the stomach, beginning
of the small intestine and end of the large intestine. Very commonly,
gastrointestinal disease is found only in the unexaminable parts of the
small and large intestines.
Surgical Gastrointestinal Biopsies
Celiotomy is necessary to obtain small and large intestinal biopsies where
endoscopic equipment cannot. Surgical biopsies are larger size and
consequently more reliable in identifying intestinal lesions. Endoscopic
biopsies are sometimes normal only to find that surgical biopsies show
disease.
Testing for Food Allergies
Tests
are available to examine for food allergy. Some tests measure for
circulating antibodies against foods. These tests are expensive and none are
reliable for making any conclusions on food allergies. Feeding test diets
with monitoring of clinical signs is more reliable than any laboratory tests
for dietary allergies. (Laboratory tests for food allergies include RAST
tests for identifying specific foods causing an allergy, blood tests to
measure levels of the IgA antibody coating and protecting the mucosal
surface of the intestine, and skin tests evaluating for allergies to
specific foods.)
Testing Gastrointestinal Functions
The most
useful tests for evaluating gastrointestinal disease give information on
function, not on anatomic or pathologic changes such as from radiographs and
biopsies. Information on function also tells how to best manage a problem.
Few such tests are available for use on dogs and cats. One function test
determines whether pancreatic secretion is adequate to digest a meal. That
test, measurement of trypsin-like-immunoreactivity (TLI), is an easily
performed blood test. Another test measures breath hydrogen to evaluate
adequacy of carbohydrate digestion and absorption. Breath hydrogen results
also are useful in identifying small intestinal bacterial overgrowth.
Function tests are available for determining transit rate through the
gastrointestinal tract. Information on these three functions directs use of
specific treatment with drugs that a veterinarian cannot reliably prescribe
on the results of biopsies. No other tests are available and reliable for
gaining any useful information on gastrointestinal disease in animals.
Evaluation of Normal Test Results
As
already stated, results of all tests will probably be normal in a dog or cat
with chronic gastrointestinal disease. With normal test results how does one
understand and explain the animal's disease? The animals with either normal
test findings or inflammatory changes in the gastrointestinal biopsy are the
vast majority of the animals with gastrointestinal disease. Other than
animals with cancer how do the common problems develop in this vast majority
of animals?
Is Irritable Bowel Syndrome a Problem in Dogs?
Diarrhea
and vomiting caused by an adverse food reaction are often difficult to
evaluate and reasonably explain. Diagnostic tests are usually normal which
can be frustrating. Dogs who defy an easy diagnosis are sometimes concluded
to have "irritable bowel syndrome." This problem has other names such as
nervous colitis, spastic colitis, mucous colitis or another name that
implies a neurologic or behavioral disease. Some veterinarians believe that
dogs have this human problem where abnormal intestinal motility causes
irregular bowel habits.
Cause of Irritable Bowel Syndrome
The
cause of irritable bowel syndrome in humans is unknown; complete
examinations show normal findings. Then by exclusion of all known diseases
the diagnosis is made. Physicians believe that a psychological problem causes the disease’s alternating
signs of diarrhea and constipation. For affected humans there is no
effective treatment. Medical specialists do not agree whether such a disease
really exists; half do not believe in such a problem. Do dogs have a similar
problem and if so what can be done about it, if anything?
Diarrhea Worsened by Increased Physical Activity
There
are logical reasons for believing that irritable bowel syndrome can afflict
dogs. Typically, dogs with known gastrointestinal diseases causing diarrhea
can produce formed bowel movements during confinement where they receive
little exercise. With exercise diarrhea returns. It is easy to conclude that
exercise is the cause for a nervous colitis or irritable bowel syndrome.
Many dogs are hospitalized for evaluation and management of diarrhea. After
overnight cage confinement the diarrhea disappears, with normal bowel
movements seen the following morning. These dogs are often discharged
without anything being done because they no longer have diarrhea. On
arriving home increased activity and excitement causes diarrhea to reappear.
It becomes easy to attribute the diarrhea to a nervous or psychological
problem. Another example is illustrated in dogs that are relatively inactive
until weekends when their owners are home and physical activity increases,
resulting in diarrhea, while during weekday inactivity bowel movements are
normal. Do these dogs have irritable bowel syndrome? Can they be given a
human problem if medical examinations show nothing wrong? Cage confinement
or exercise restriction for dogs with diarrhea results in fewer abnormal
bowel movements. They improve because physical inactivity causes food to
move more slowly through the gastrointestinal tract. The slower movement
allows for more thorough assimilation of a meal with the result being
optimal absorption of nutrients and water. This results in formed feces.
Thus dogs and other animals can compensate when they have a gastrointestinal
system problem causing diarrhea. They compensate most when they are
inactive.
Evaluate Patients for A Recognized Disease Entity
The dog
with diarrhea caused by increased physical activity does not have irritable
bowel syndrome. It usually has a dietary intolerance that is not severe so
that the dog can compensate during restriction of physical activity. Many
dogs referred to University of California School of Veterinary Medicine
Teaching Hospital (VMTH) for further evaluation of chronic diarrhea are sent
in with a provisional diagnosis of irritable bowel syndrome. Many of these
dogs had been treated with antidiarrheal drugs, but none with success. Most
medications contained a tranquilizer and an intestinal muscle relaxant, a
drug used in human medicine for the same problem (with no proven efficacy,
however). These patients are subsequently evaluated and a reasonable
explanation was found for the problem. The explanation was never irritable
bowel syndrome. Most were managed successfully with a controlled diet. These
dogs invariably recovered and had no need for long-term drug treatment.
Management of Unknown Causes for Diarrhea
There is
no evidence that dogs suffer from irritable bowel syndrome. For a dog with
persistent diarrhea a better explanation can be found. There may be such an
entity in people but if there is, the symptoms of the problem in humans are
different from those in dogs. Chronic gastrointestinal problems in dogs do
not cause signs that alternate between diarrhea and constipation. Other
signs in people include bloating and abdominal pain or discomfort. Owners do
not report these signs in the dogs referred with a diagnosis of irritable
bowel syndrome. Treatment with antidiarrheal drugs is ineffective in people
with the problem. How could they be effective in dogs, especially when there
is no comparable disease to treat? Most of the dogs referred to the VMTH
with suspected irritable bowel syndrome are successfully treated. They are
fed a controlled diet containing no foods to which there is an adverse
reaction. When fed controlled diets affected dogs no longer have problems
when their physical activity increases or when they are subjected to stress.
Extreme stress and exercise can cause diarrhea. Hunting dogs often work
strenuously, which can cause diarrhea for probably the same reasons as for
marathon runners. No one understands why this diarrhea develops. The
pathogenesis of this problem is different from changes in humans with
irritable bowel syndrome.
References
1. Guilford, W. Grant. 1996. Approach to Clinical Problems in Gastroenterology. In Strombeck’s Small Animal Gastroenterology, edited by W. Grant Guilford, Sharon A. Center, Donald R. Strombeck, David A. Williams and Denny J. Meyer, 50-76. Philadelphia: W.B. Saunders.
2. Guilford, W. Grant. 1996. Adverse Reactions to Food. In Strombeck’s Small Animal Gastroenterology, edited by W. Grant Guilford, Sharon A. Center, Donald R. Strombeck, David A. Williams and Denny J. Meyer, 436-450. Philadelphia: W.B. Saunders.
3. Marsh, Michael N. 1992. Gluten, Major Histocompatibility Complex, and the Small Intestine. Gastroenterology 102:330-354.
4. Guilford, W. Grant and Donald R. Strombeck. 1996. Gastrointestinal Tract Infections, Parasites, and Toxicoses. In Strombeck’s Small Animal Gastroenterology, edited by W. Grant Guilford, Sharon A. Center, Donald R. Strombeck, David A. Williams and Denny J. Meyer, 411-432. Philadelphia: W.B. Saunders.
5. Strombeck, Donald R. Unpublished study.
6. Williams, David A. and W. Grant Guilford. 1996. Procedures for the Evaluation of Pancreatic and Gastrointestinal Tract Diseases. In Strombeck’s Small Animal Gastroenterology, edited by W. Grant Guilford, Sharon A. Center, Donald R. Strombeck, David A. Williams and Denny J. Meyer, 77-113. Philadelphia: W.B. Saunders.
7. Guilford, W. Grant. 1996. Motility Disorders of the Bowel. In Strombeck’s Small Animal Gastroenterology, edited by W. Grant Guilford, Sharon A. Center, Donald R. Strombeck, David A. Williams and Denny J. Meyer, 532-539. Philadelphia: W.B. Saunders.