Definition

A group of chronic enteropathies characterized by persistent or intermittent gastrointestinal (GI) signs with histopathologic evidence of intestinal inflammation. The form of IBD is generally categorized by the predominant mucosal cellular infiltrate, such as lymphocytic-plasmacytic enteritis, eosinophilic enteritis, or granulomatous enteritis.

Pathophysiology

• Poorly understood but likely due to complex interplay between mucosal immunity and environmental factors (i.e., dietary and bacterial antigens) in genetically-susceptible dogs. Aberrant host immune responses are likely triggered by antigens derived from members of the commensal microbiota.
• Damage results from the elaboration of cytokines, release of proteolytic and lysosomal enzymes, complement activation secondary to immune complex deposition, and generation of oxygen free radicals which damage the intestinal epithelial barrier.
• Host genetic susceptibility involving defects in innate immunity is suspected in dogs, and possibly cats.

Systems Affected

• Gastrointestinal
• Hepatobiliary
• Hemic/Lymphatic/Immune-rarely
• Musculoskeletal-rarely
• Ophthalmic-rarely
• Respiratory-rarely
• Skin/Exocrine-rarely

Genetics

Defects in some host susceptibility genes have been identified in German shepherd dog, boxer, and soft-coated Wheaton terrier.

Incidence/Prevalence

IBD is the most common histopathologic diagnosis in dogs and cats with chronic GI signs.

Geographic Distribution

N/A

Signalment

Signs

Causes

• Pathogenesis is unknown but most likely multifactorial.
• Etiology likely involves complex interactions between host genetics, mucosal immunity, and environmental (diet, intestinal bacteria) factors.

Risk Factors

Current hypotheses suggest that IBD is a multifactorial disorder conditioned by genetic, immunologic, and environmental factors.

Differential Diagnosis

• Cats-hyperthyroidism, intestinal neoplasia (especially small cell lymphoma), adverse food reactions, granulomatous FIP and other viral infections (e.g., FeLV and FIV), renal and hepatic insufficiency, exocrine pancreatic insufficiency, intestinal parasitism, and antibiotic responsive enteropathy (ARD) are primary differentials.
• Dogs-intestinal neoplasia, motility disorders, adverse food reactions, lymphangiectasia, exocrine pancreatic insufficiency, intestinal parasitism, and ARD are primary differentials.

CBC/Biochemistry/Urinalysis

• Results may be unremarkable; these tests more often serve to eliminate other differential diagnoses.
• Mild, nonregenerative anemia of chronic disease. Mild leukocytosis ± a left shift is sometimes seen with mucosal disruption (e.g., erosions). Mild peripheral eosinophilia may be seen in dogs and cats with eosinophilic enteritis, food allergy, and intestinal parasites amongst other causes.
• Cats with IBD may show alterations in serum total protein (i.e., hyperproteinemia) and albumin concentrations and with increased liver enzyme (e.g., ALT and/or ALP) activities.
• Hypoproteinemia is more common in dogs with IBD than in cats.
• Cobalamin deficiency reported in both dogs and cats with involvement of the ileum.

Other Laboratory Tests

• Useful to eliminate other differentials.
• Dogs-tests include evaluation of exocrine pancreatic function (cTLI), serology for pancreatitis (Spec cPL), and serum cobalamin and folate assays to localize small intestinal disease.
• Cats-T₄ and FeLV/FIV serology are recommended; fasting serum TLI (if exocrine pancreatic insufficiency is suspected); serology for pancreatitis (Spec fPL), and serum cobalamin and folate assays to localize small intestinal disease.

Imaging

• Survey abdominal radiographs-usually unremarkable. Radiographic imaging is most useful in documenting abnormalities in organs outside of the alimentary tract.
• Barium contrast studies-may reveal mucosal abnormalities and thickened bowel loops. Normal findings do not eliminate the possibility of IBD.
• Ultrasonography-may indicate increased intestinal wall thickness (particularly the muscularis propria and submucosal layers) and mesenteric lymphadenopathy. However, these abnormalities, even if present, are not specific for IBD.

Diagnostic Procedures

• Perform an elimination dietary trial to eliminate adverse food reactions. If GI signs resolve within 2 weeks, then a diagnosis of adverse food reaction is made and no further diagnostic work-up is required.
• Always perform fecal flotations for nematode and protozoal parasites.
• Definitive diagnosis of IBD requires intestinal biopsy and histopathology, usually obtained via endoscopy.
• Exploratory laparotomy may be indicated if endoscopy is unavailable or to collect full-thickness mucosal specimens.
• Use clinical scoring indices such as the canine inflammatory bowel disease activity index (CIBDAI) to define initial IBD disease burden and to assess response to therapy. Concurrent evaluation of C-reactive protein serves as a useful biomarker of active inflammation in dogs.

Pathologic Findings

Morphologic evidence of mucosal inflammation including epithelial changes, architectural distortion (e.g., erosion/ulceration, crypt hyperplasia, fibrosis, loss of colonic goblet cells), and increased lamina propria cellularity. New histopathologic guidelines for defining the severity of gastrointestinal inflammation have been recently described.

Appropriate Health Care

Outpatient, unless the patient is debilitated from dehydration, hypoproteinemia, or cachexia.

Nursing Care

• If the patient is dehydrated or must have food restricted because of intractable vomiting, any balanced fluid such as lactated Ringer's solution is adequate (for a patient without other concurrent disease); otherwise, select fluids on the basis of secondary diseases.
• If there is severe hypoalbuminemia from protein-losing enteropathy, consider use of colloids, such as hetastarch, to control effusions.

Activity

No restrictions

Diet

• Feed an intact protein or hydrolysate elimination diet to help reduce intestinal inflammation.
• Correct hypocobalaminemia by means of weekly parenteral cobalamin injections for the first 6 weeks and thereafter every 2–3 weeks or as needed based on repeat testing of cobalamin concentrations.
• Fiber supplementation (e.g., fermentable fiber such as pumpkin, Metamucil) is suggested in dogs and cats with colitis.
• Fish oil (n-3 fatty acids) as a free radical scavenger to reduce intestinal inflammation.
• Probiotics may be of benefit in some animals but are clinically unproven at this time. These supplements must be given continuously over several weeks for potential benefit to be realized.

Client Education

• Emphasize to the client that IBD is not cured but is controllable in most instances.
• Relapses are common; clients should be patient during the various food and medication trials that are often necessary to get the disease under control.

Surgical Considerations

No surgical procedures are available for relief of IBD in veterinary patients.

Drug(s) Of Choice

• See discussion under specific diseases.
• Affected animals with an immune cellular infiltrate should be treated with immunosuppressive drug regimens. Dogs with granulomatous colitis associated with AIEC are treated with fluoroquinolone antibiotics (see chapter, Colitis, Histiocytic Ulcerative, for details).

Contraindications

If secondary problems are present, avoid therapeutic agents that might be contraindicated for those conditions.

Precautions

See discussion under specific diseases

Possible Interactions

See discussion under specific diseases

Alternative Drug(s)

See discussion under specific diseases

Patient Monitoring

• Periodic (q2–4 weeks) physical and laboratory evaluations may be necessary until the patient's condition stabilizes. Serum albumin provides important prognostic information in dogs; serum cobalamin deficiency will delay complete clinical recovery in both dogs and cats.
• Monitor serum cobalamin concentrations in hypocobalaminemic dogs and cats.
• No other follow-up may be required except yearly physical examinations and assessment during relapse.

Prevention/Avoidance

N/A

Possible Complications

Dehydration, malnutrition, adverse drug reactions, hypoproteinemia, hypocobalaminemia, anemia, and diseases secondary to therapy or resulting from the above-mentioned problems.

Expected Course and Prognosis

• Generally a good-to-excellent short-term prognosis.
• Poor long-term prognosis in dogs with IBD has been associated with severe clinical disease, marked endoscopic (duodenal) abnormalities, ascites, and hypoalbuminemia.

Associated Conditions

• See discussion under specific diseases.
• Cats may demonstrate concurrent inflammatory lesions in the liver and/or pancreas (so called “triaditis”).

Age-Related Factors

• See discussion under specific diseases.
• The workup and differentials are essentially the same, regardless of age.
• Some differentials are more likely in younger individuals (i.e., intestinal parasitism vs. neoplasia).
• Counsel clients about breeding and monitoring for the appearance of other diseases.

Zoonotic Potential

N/A

Pregnancy/Fertility/Breeding

See discussion under specific diseases

See Also

• Colitis, Histiocytic Ulcerative
• Gastroenteritis, Eosinophilic
• Gastroenteritis, Lymphocytic-Plasmacytic

Abbreviations

• ALP = alkaline phosphatase
• ALT = alanine aminotransferase
• ARD = antibiotic responsive diarrhea
• CIBDAI = canine IBD activity index
• FeLV = feline leukemia virus
• FIP = feline infectious peritonitis
• FIV = feline immunodeficiency virus
• GI = gastrointestinal
• IBD = inflammatory bowel disease
• Spec cPL or fPL = canine or feline pancreatic lipase activity
• T₄ = thyroxine
• TLI = trypsin-like immunoreactivity

Internet Resources

Veterinary Information Network: http://www.vin.com/VIN.plx

Author Albert E. Jergens

Consulting Editor Stanley L. Marks

Client Education Handout Available Online