Definition

• The most common form of inflammatory bowel disease characterized by lymphocyte and plasma cell infiltration into the lamina propria of the stomach and intestine; usually accompanied by other criteria of mucosal inflammation.
• Less commonly the infiltrates may extend into the submucosa and muscularis.

Pathophysiology

• An aberrant immune response to environmental stimuli likely resulting in loss of mucosal homeostasis; alterations in intestinal microbiota (i.e., dysbiosis) maybe a trigger.
• Continued antigen exposure, coupled with dysregulated inflammation, results in disease, although the exact mechanisms and patient factors remain unknown.

Systems Affected

• Gastrointestinal-typically small intestine and occasionally stomach; the colon can be independently or simultaneously affected.
• Extra-intestinal manifestations of inflammation are occasional seen (e.g., mild thrombocytopenia) although they are not well characterized.

Genetics

Basenjis, Lundehunds, and soft-coated Wheaten terriers have familial forms of inflammatory bowel disease.

Incidence/Prevalence

The most common form of IBD affecting dogs and cats.

Signalment

Signs

Causes

Pathogenesis is likely multifactorial and involves complex interactions between genetic, immunologic, and environmental (i.e., microbiota) factors.

Risk Factors

See “Causes”

Differential Diagnosis

• Other infiltrative inflammatory bowel conditions (e.g., eosinophilic gastroenteritis, granulomatous IBD).
• Food hypersensitivity.
• Metabolic disorders.
• Neoplasia.
• Infectious diseases (e.g., histoplasmosis, toxoplasmosis, giardiasis, salmonellosis, Campylobacter enteritis, and bacterial overgrowth).
• Miscellaneous diseases (e.g., lymphangiectasia, gastrointestinal motility disorders, and exocrine pancreatic insufficiency).
• In the cat, consider hyperthyroidism, systemic viral infection (e.g., FeLV, FIV, FIP), and chronic pancreatitis.

CBC/Biochemistry/Urinalysis

• Often normal.
• Mild nonregenerative anemia and mild leukocytosis with or without a mild left shift.
• Hypoproteinemia is more common in dogs than cats with IBD.

Other Laboratory Tests

• Alterations in serum cobalamin and folate may serve to localize enteric regions of small intestinal inflammation.
• Serum pancreatic specific lipase to screen for pancreatic inflammation.
• Fecal alpha1-proteinase inibitor to evaluate for protein-losing enteropathy.
• Trypsin-like immunoreactivity to evaluate for exocrine pancreatic insufficiency.
• Cats-T₄ and FeLV/FIV/toxoplasmosis serology are recommended to screen for infectious causes for gastrointestinal signs.

Imaging

• Survey abdominal radiographs are usually normal.
• Barium contrast studies occasionally reveal mucosal abnormalities and thickened bowel loops but are typically not helpful in establishing a definitive diagnosis.

Diagnostic Procedures

• Initiate a hypoallergenic dietary trial to rule out adverse food reactions; if signs resolve then additional diagnostics are not necessary.
• Always perform direct and indirect fecal examinations for parasites.
• Definitive diagnosis requires mucosal biopsy and histopathology, usually obtained via endoscopy.
• Exploratory laparotomy or laparoscopy may be indicated when portions of the GI tract, unapproachable by endoscopy, are involved or if abdominal organomegaly, lymphadenomegaly, or masses are present.
• Clinical assessment of disease severity using the canine IBD activity index (CIBDAI) is a useful tool.

Pathologic Findings

• Grossly, stomach and intestinal appearance can range from normal to edematous, thickened, and ulcerated.
• The hallmark histopathologic finding is an infiltrate of lymphocytes and plasma cells in the lamina propria; architectural changes including villus atrophy, fusion, fibrosis, crypt abscessation and lymphangiectasia may be present to varying degrees.
• The distribution may be patchy, so numerous biopsy specimens are necessary to make the diagnosis.

Appropriate Health Care

• Outpatient, unless the patient is debilitated from dehydration, hypoproteinemia, or cachexia.
• Monitor therapeutic responses using CIBDAI scores.

Nursing Care

• If the patient is dehydrated or must be NPO because of severe vomiting, a balanced crystalloid such as lactated Ringer's solution is adequate; additional electrolyte supplementation may be necessary if alterations are present (e.g., potassium chloride).
• Colloids (dextrans or hetastarch) should be given if severe hypoalbuminemia from protein losing enteropathy is present.

Activity

No restrictions

Diet

• Dietary therapy with an elimination or hydrolyzed diet is an essential component of patient management.
• Patients with severe intestinal involvement and protein-losing enteropathy may require total parenteral nutrition until stable.
• Highly digestible diets decrease the intestinal antigenic load, thus helping to reduce mucosal inflammation; appropriate diet therapy can contribute to clinical remission and can be used as a maintenance diet.
• Modification of the n3:n6 fatty acid ratio may also help to modulate the inflammatory response.
• Parenteral cobalamin supplementation is essential if serum levels are subnormal. Deficiencies in cobalamin can contribute to clinical signs and limit the effectiveness of dietary and medical therapy.
• Numerous commercial elimination diets that meet the above criteria are available for dogs and cats; home-cooked diets are also an excellent option but are more time-consuming for owners.
• Use fiber supplementation in dogs and cats with colitis.

Client Education

• IBD is more likely to be controlled rather than cured, as relapses are common.
• Patience is required during the various food and medication trials that are often necessary.

Drug(s) Of Choice

• Corticosteroids-the mainstay of treatment for idiopathic lymphocytic-plasmacytic enteritis; prednisone or prednisolone is used most frequently (1 mg/kg PO q12h) in dogs and cats; cats may require a higher dose to control their disease. Gradually taper the corticosteroid dose after 2–4 weeks of induction therapy when clinical signs are resolved; relapses are common if patients are tapered too quickly. Maintenance dosages q48–72h may be necessary in some patients. Cats may respond better to prednisolone than prednisone. Budesonide, a locally active steroid, may be used in patients that cannot tolerate the systemic side effects of prednisone. Parenteral steroids may be needed in severe cases in which oral absorption may be limited.
• Azathioprine (2 mg/kg q24–48h PO in dogs; not recommended in cats)-an immunosuppressive drug that can be used to allow a reduction in corticosteroid dose; delayed onset of activity (up to 3 weeks) limits effectiveness in acute cases.
• Chlorambucil (2 mg q48–72h PO in cats) is an effective alternative to azathioprine.
• Metronidazole-has antibacterial and antiprotozoal properties; some evidence that it also has immune-modulating effects in rodents; the dosage for IBD in dogs and cats is 10 mg/kg PO q12h.

Alternative Drug(s)

• Cyclosporine-may be useful in the therapy of refractory cases of lymphocytic-plasmacytic gastroenteritis; using Atopica, 2–5 mg/kg PO q12h for dogs, 1–4 mg/kg q12–24h for cats; dosage is very individualized so monitoring trough levels is recommended.
• Sulfasalazine-a sulfa analog that is broken down by luminal bacteria into sulfapyridine and mesalamine, the latter of which provides anti-inflammatory effects in the colon; dosage for dogs with colonic IBD is 10–30 mg/kg PO q8–12h. Use cautiously in cats and at reduced dosage due to the potential for salicylate toxicity.

Precautions

• Azathioprine-causes bone marrow suppression, especially in cats; routine CBCs are recommended at 2 weeks, 1 month, and then bimonthly; bone marrow suppression is typically reversible if the drug is discontinued as soon as suppression is noted.
• Metronidazole-can cause reversible neurotoxicity at high dosages; discontinuation of the drug usually reverses the neurologic signs.
• Cyclosporine-can cause vomiting, gingival hyperplasia, and papillomatosis; associated with the development of lymphoma in humans.

Possible Interactions

• Cyclosporine can interfere with the metabolism of phenobarbital and phenytoin.
• Ketoconazole, erythromycin, and cimetidine can decrease hepatic metabolism of cyclosporine.
• Any drugs that are potentially nephrotoxic should be used with caution in conjunction with cyclosporine.

Patient Monitoring

• Severely affected patients on bone marrow suppressive medications require frequent monitoring (see above); adjust medications during these visits based on bloodwork and clinical signs.
• Check patients with less severe disease 2–3 weeks after their initial evaluation and then monthly to bimonthly until medications are tapered and clinical signs are resolved.

Prevention/Avoidance

When a food intolerance or allergy is suspected or documented, avoid that particular item and adhere strictly to dietary restriction.

Possible Complications

• Weight loss and debilitation in refractory cases.
• Iatrogenic hyperadrenocorticism and steroid side effects.
• Bone marrow suppression, pancreatitis, hepatopathy, or anorexia can be caused by azathioprine.
• Vomiting, diarrhea, and anorexia with cyclosporine; decreasing the dosage temporarily typically will result in resolution of gastrointestinal signs.
• Keratoconjunctivitis sicca with sulfasalazine.

Expected Course and Prognosis

• Dogs and cats with mild-to-moderate inflammation have a good-to-excellent prognosis for full recovery.
• Patients with severe infiltrates, particularly if other portions of the GI tract are involved, have a more guarded prognosis.
• Other prognostic indices associated with negative long-term outcome include severe mucosal lesions on endoscopy, hypocobalaminemia, and hypoalbuminemia.
• Often the initial response to therapy sets the tone for a given individual's ability to recover.

Pregnancy/Fertility/Breeding

• Corticosteroids have been associated with increased incidence of congenital defects, abortion, and fetal death.
• Azathioprine has been used safely in pregnant women, and may be a good substitute for corticosteroids in pregnant animals.
• Sulfasalazine should be used with extreme caution during pregnancy.

See Also

• Gastroenteritis, Eosinophilic
• Inflammatory Bowel Disease

Abbreviations

• CIBDAI = canine IBD activity index
• FeLV = feline leukemia virus
• FIP = feline infectious peritonitis
• FIV = feline immunodeficiency virus
• GI = gastrointestinal
• IBD = inflammatory bowel disease

Client Education Handout Available Online