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.
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.
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 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.
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 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 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 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 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.
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.
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.
Unexplained shivering can be a sign of adverse food reaction. The shivering results from discomfort produced by gastrointestinal tract spasms or distention.
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 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.
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 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.
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3. Marsh, Michael N. 1992. Gluten, Major Histocompatibility Complex, and the Small Intestine. Gastroenterology 102:330-354.
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5. Strombeck, Donald R. Unpublished study.
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