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Basics ⬇

Basics

Definition

  • Colitis-inflammation of the colon (large intestine). Colitis may be acute and self-limiting or chronic.
  • Colitis does not infer causality, and an underlying cause of the colitis should be investigated, particularly in chronic cases.
  • Proctitis-inflammation of the rectum.

Pathophysiology

  • Inflammation of the colon causes accumulation of inflammatory cytokines, disrupts tight junctions between epithelial cells, stimulates colonic secretion, stimulates goblet cell secretion of mucus, and disrupts motility.
  • These mechanisms reduce the ability of the colon to absorb water and electrolytes, and store feces, which causes frequent diarrhea, often with mucus and/or frank blood.

Systems Affected

Gastrointestinal

Genetics

  • Breeds predisposed to histiocytic ulcerative colitis (granulomatous colitis) include boxers, French bulldogs, and perhaps border collies.
  • German shepherd dogs are predisposed to perianal fistulae that can be associated with colitis.

Incidence/Prevalence

  • Approximately 30% of dogs with chronic diarrhea examined at one university hospital.
  • 75% of dogs with a food-responsive enteropathy had clinical signs of colitis.
  • Prevalence of colitis is probably higher than perceived, because many diarrheic dogs and cats can have mixed bowel diarrhea (component of small and large bowel diarrhea).

Geographic Distribution

N/A except for certain infectious diseases (pythiosis: predominantly Gulf Coast and southeast United States although becoming more widespread; histoplasmosis: Midwest, eastern United States).

Signalment

Species

Dog and cat

Breed Predilections

  • Boxer dogs, French bulldogs, border collies (granulomatous colitis).
  • German shepherd dogs: perianal fistulas and concurrent colitis.

Mean Age and Range

Any age; boxers, French bulldogs usually younger (<2 years of age).

Signs

Historical Findings

  • Fecal consistency can be variable from semiformed to liquid.
  • Marked increase in frequency of defecation (6–15 times per day) with small fecal volume.
  • Tenesmus.
  • Increased fecal mucus.
  • Hematochezia; cats may have formed feces with hematochezia.
  • Occasional dyschezia (painful defecation).
  • Vomiting in approximately 30% dogs.
  • Weight loss is less common, but can be seen with colonic lymphoma, histoplasmosis, and pythiosis.

Physical Examination Findings

  • Usually unremarkable.
  • Rectal examination may reveal a thickened and irregular colorectal mucosa.
  • Dogs with GC may show systemic signs of weight loss and anorexia.

Causes

  • Dietary: food-responsive enteropathy is a common and important cause of colitis; dietary indiscretion; food intolerance.
  • Drug administration (antibiotics, NSAIDs).
  • Infectious-Trichuris vulpis, Entamoeba histolytica, Balantidium coli,, Tritrichomonas foetus., Clostridium perfringens and Clostridium difficile, Campylobacter jejuni and Campylobacter coli, Yersinia enterocolitica, Prototheca, Histoplasma capsulatum, and pythiosis/phycomycosis.
  • Traumatic-foreign body, abrasive material.
  • Inflammatory-secondary to pancreatitis (transverse colitis).
  • Inflammatory/immune-IBD (lymphoplasmacytic, eosinophilic, granulomatous) colitis.

Diagnosis ⬆ ⬇

Diagnosis

Differential Diagnosis

  • Neoplasia-colonic lymphoma, adenocarcinoma, sarcomas.
  • Irritable bowel syndrome.
  • Colorectal polyps do not typically cause signs of colitis, but instead cause hematochezia in association with formed stool that is defecated at normal frequency.
  • Cecal inversion.
  • Ileocecocolic intussusception.

CBC/Biochemistry/Urinalysis

  • Results usually unremarkable; neutrophilia with a left shift can be seen with severe inflammatory causes; eosinophilia secondary to eosinophilic colitis, parasitism, histoplasmosis, and pythiosis/phycomycosis.
  • Mild microcytic, hypochromic anemia may occur secondary to chronic intestinal bleeding and iron deficiency.
  • Hyperglobulinemia in some patients (especially cats) with chronic disease.

Other Laboratory Tests

  • Examination of fecal centrifugation flotation, direct fecal smear (only on fresh diarrheic feces), fecal bacterial toxin immunoassays (C. perfringens enterotoxin and C. difficile toxins A and B), and PCR for bacteria and toxin genes when indicated, serum ELISA test for Pythium when indicated.
  • Rectal scraping for cytology for Histoplasma organisms.
  • Fecal PCR or In Pouch TF medium for culture of Tritrichomonas foetus.

Imaging

  • Abdominal radiographs-usually unremarkable.
  • Abdominal ultrasonography-may reveal masses, diffuse thickening or altered architecture of the colon, or enlarged associated lymph nodes.
  • Contrast studies-barium may be administered transcolonically to evaluate the colorectal mucosa for irregularities or filling defects and colorectal strictures; however, the procedure is rarely indicated in dogs and cats with colitis and is of low sensitivity in general.

Other Diagnostic Procedures

  • Colonoscopy with biopsy-procedure of choice for diagnosis of chronic or refractory cases. Animals must be adequately prepared for colonoscopy by being fasted and administered osmotic cathartics such as Osmoprep or Golytely; mucosal changes visible grossly in animals with colitis include disappearance of submucosal blood vessels, granular appearance of mucosa, hyperemia, excessive mucus, ulceration, pinpoint hemorrhage (small ulcerations), or mass(es).
  • One should always obtain multiple biopsy specimens from multiple locations (ascending colon, transverse colon, descending colon, and rectum) because the extent of mucosal change assessed histologically does not necessarily reflect the severity of the colitis or proctitis.

Pathologic Findings

Histopathologic findings depend on the histologictypeofcolitis-lymphoplasmacytic, eosinophilic, or histiocytic represent the most common subtypes; hyperplastic mucosa may be seen with irritable bowel syndrome; various infectious agents may be seen with special stains.

Treatment ⬆ ⬇

Treatment

Appropriate Health Care

Outpatient medical management unless diarrhea is severe enough to cause dehydration and warrant hospitalization.

Nursing Care

Give dehydrated patients balanced electrolyte solution with potassium IV or SC.

Diet

  • There is no inherent benefit to fasting patients with diarrhea, unless the cause of the diarrhea has an osmotic component.
  • Animals that do not have severe clinical signs can be managed with an elimination diet or hypoallergenic diet for 2 weeks. The response to dietary therapy is typically seen within the first 5–7 days following dietary implementation. Obtain a comprehensive dietary history to optimize selection of a novel, single protein source diet. Strict dietary compliance is pivotal during this trial period to optimize interpretation of response.
  • Fiber supplementation with poorly fermented fiber (e.g., bran and alpha-cellulose) is recommended to increase fecal bulk, improve colonic muscle contractility, and bind fecal water to produce formed feces.
  • Some fermentable fiber sources (e.g., psyllium or a diet containing beet pulp or fructooligosaccharides) may be beneficial-short-chain fatty acids produced by fermentation may be beneficial for colonocyte function.

Client Education

Treatment may be intermittent and long-term in patients with inflammatory/immune-mediated colitis. Recurrences can be seen, particularly when drug therapy is being tapered.

Surgical Considerations

Segments of colon severely affected by fibrosis from chronic inflammation and subsequent stricture formation may need surgical excision, especially in patients with the granulomatous form of the disease; cecal inversion and ileocecocolic intussusception require surgical intervention; pythiosis/phycomycosis often requires surgical excision or debulking.

Medications ⬆ ⬇

Medications

Drug(s) Of Choice

Antimicrobial Drugs

  • Trichuris -fenbendazole (50 mg/kg PO q24h for 5 consecutive days, repeat in 3 months).
  • Entamoeba, Balantidium-metronidazole (25 mg/kg PO q12h for 5–7 days).
  • Tritrichomonas foetus-Ronidazole (30 mg/kg q24h for 14 days).
  • Clostridium perfringens.-metronidazole (10 mg/kg PO q12h for 5 days), tylosin (5–10 mg/kg PO q24h for 5 days), ampicillin or amoxicillin (20 mg/kg PO q8h for 5 days).
  • Clostridium difficile-metronidazole (10 mg/kg PO q12h for 5 days),
  • Campylobacter spp.-Erythromycin (10–15 mg/kg PO q8h), or azithromycin (5–10 mg/kg PO q24h) can be given for 7–10 days. Azithromycin is better tolerated than erythromycin,
  • Yersinia spp.-select the drug on the basis of bacterial culture and sensitivity testing.
  • Prototheca-no known treatment.
  • Histoplasma-itraconazole (dogs, 10 mg/kg PO q24h; cats, 5 mg/kg PO q12h; several months of therapy is necessary); amphotericin B (0.25–0.5 mg/kg slow IV q48h up to cumulative dose of 4–8 mg/kg) in advanced cases.
  • Pythiosis-itraconazole (10 mg/kg PO q24h) and terbinafine (10 mg/kg PO q24h) are the drugs of choice following surgical debridement of affected portions of bowel. Antifungal therapy is often administered for 3–4 months or longer in affected animals.

Anti-inflammatory and Immunosuppressive Drugs for Inflammatory/Immune Colitis

  • Sulfasalazine (dogs, 25–40 mg/kg PO q8h for 3–6 weeks with a progressive tapering of the dose throughout the course of drug therapy; cats, 20 mg/kg PO q12h for 3 weeks). Use with caution, particularly in cats, in which adverse effects on the gastrointestinal tract and kidneys can be observed. Sulfasalazine has been associated with irreversible KCS.
  • Corticosteroids-prednisone for dogs and prednisolone for cats: 1–2 mg/kg PO q12h for 5–7 weeks with gradual, progressive tapering of dose. Most cats can be started off on 5 mg (per cat) q12h with gradual taper. Never use more than 50 mg total of prednisone (per day) for any animal, regardless of size.
  • Azathioprine (dogs) 1–2 mg/kg PO q24h for 10–14 days followed by a taper to 1–2 mg/kg q48h for 4–6 weeks. The drug is markedly myelosuppressive in cats and should be avoided even though a lower dose (0.3 mg/kg PO q48h) for this species has been published.
  • Chlorambucil is an effective immunomodulator in both dogs and cats and is usually administered in conjunction with prednisone or prednisolone. Several dosing regimes have been published: cats, 2 mg per cat q3–4 days for 2–3 months (or longer if managing lymphoma) or 15 mg/m2 given for 4 consecutive days every 3 weeks for 2–3 months; dogs, 0.1–0.2 mg/kg PO q24h for 8–12 weeks for immune disease, with gradual tapering of dose over the course of therapy.
  • Cyclosporine (5 mg/kg PO q12–24h for 6 weeks for immune disease).
  • Sulfasalazine or other 5-ASA drugs-may be a reasonable consideration following assessment to dietary therapy for 2 weeks, and is typically reserved for cases with mild colitis before considering prednisone therapy.
  • Granulomatous colitis is managed with fluoroquinolones such as enrofloxacin at 10 mg/kg q 24h for 6–8 weeks.
  • Reconsider the diagnosis carefully in dogs that do not respond to dietary therapy, fenbendazole administration, and tylosin therapy.

Motility Modifiers (Indicated for symptomatic relief only in animals with intractable diarrhea and must be avoided in all animals with a suspected infectious enteropathy)

Anthelminthics

  • Broad-spectrum anthelminthics such as fenbendazole (50 mg/kg q24h for 5 consecutive days) in conjunction with dietary therapy (elimination diet) for the first 2 weeks is the mainstay of therapy for most patients with chronic colitis, unless the animal is a boxer breed that should have endoscopy and biopsy to confirm the granulomatous colitis that has a different therapy and prognosis.
  • Tylosin is a highly effective antimicrobial that can be administered following assessment of response to dietary and anthelminthic therapy.

Contraindications

Anticholinergics

Precautions

  • Monitor patients on sulfasalazine for signs of keratoconjunctivitis sicca. Measure tear production (Schirmer tear test) at baseline and every 2 weeks throughout the course of therapy. Discontinue drug if tear production decreases.
  • Monitor patients on azathioprine for bone marrow suppression-CBC every 2–3 weeks; stop treatment or go to alternate day if WBC count falls below 3,000 cells/µL.
  • Azathioprine can also increase the risk of pancreatitis and should be used extremely cautiously in any dog at increased risk for pancreatitis. Azathioprine can also cause a hepatopathy.
  • Chlorambucil can cause a progressive neutropenia and a CBC should be repeated q2–3 weeks in all animals receiving this drug.
  • Cyclosporine can cause hepatotoxicity and a chemistry panel should be performed as baseline before starting the drug and repeated q2–3 months.
  • Amphotericin B is nephrotoxic and requires close assessment of renal function via urinalyses and serum biochemistry panels.
  • Enrofloxacin-resistant cases of granulomatous colitis are increasing in prevalence due to antimicrobial resistance, necessitating alternative antimicrobial therapy in select cases.

Follow-Up ⬆ ⬇

Follow-Up

Patient Monitoring

Infrequent recheck examinations or client communication by phone. Recheck of CBC is important for animals on immunomodulatory therapy.

Prevention/Avoidance

  • Avoid exposure to infectious agents (e.g., other dogs, contaminated foods, moist environments).
  • Avoid abrupt dietary changes.

Possible Complications

Recurrence of signs without treatment, when treatment is tapered, and with progression of disease.

Expected Course and Prognosis

  • Most bacterial and parasitic infectious causes have an excellent prognosis with a high likelihood of cure following therapy.
  • Prototheca-grave; no known treatment except excision.
  • Histoplasma spp.-poor in advanced or disseminated disease; mild-to-moderate cases generally respond to therapy.
  • Pythiosis/phycomycosis-poor long-term prognosis in most animals, despite surgical intervention, given advanced stage of disease at diagnosis.
  • Cecal inversion, ileocecocolic intussusception-good with surgical resection if diagnosed in a timely fashion.
  • Inflammatory-fair to good with treatment in patients with lymphoplasmacytic, eosinophilic, and granulomatous colitis.
  • Most dogs with mild to moderate nonspecific colitis respond favorable to a combination of fenbendazole, feeding of an elimination or hypoallergenic diet, and tylosin therapy.

Miscellaneous ⬆

Miscellaneous

Associated Conditions

Inflammatory/immune disease and infectious agents may also affect the small intestine concurrently.

Zoonotic Potential

Entamoeba, Balantidium, Campylobacter jejuni, Yersinia in immunosuppressed individuals.

Pregnancy/Fertility/Breeding

Caution with drug use-corticosteroids, azathioprine, cyclosporine, antifungals, and antibiotics.

Synonyms

  • Inflammatory bowel disease (IBD)
  • Large bowel diarrhea

See Also

Abbreviations

  • 5-ASA = 5-aminosalicylic acid
  • GC = granulomatous colitis
  • KCS = keratoconjunctivitis sicca
  • NSAID = nonsteroidal anti-inflammatory drug
  • WBC = white blood cell

Author Stanley L. Marks

Consulting Editor Stanley L. Marks

Client Education Handout Available Online

Suggested Reading

Marks SL, Kather EJ, Kass PH, et al. Genotypic and phenotypic characterization of Clostridium perfringens and Clostridium difficile in diarrheic and healthy dogs. J Vet Intern Med 2002, 16:533–540.

Parnell NK. Chronic colitis. In: Bonagura JD, Twedt DC, eds., Current Veterinary Therapy XIV. St. Louis, MO: Elsevier, 2009, pp. 515–520.

Washabau RJ, Holt DE. Diseases of the large intestine. In: Ettinger SJ, Feldman EC, eds., Textbook of Veterinary Internal Medicine, 6th ed. St. Louis, MO: Elsevier, 2005, pp. 1378–1408.