Inflammatory Bowel Disease

Description

Inflammatory bowel disease (IBD) is an idiopathic group of disorders characterised by intestinal inflammatory changes, associated with persistent or recurrent gastrointestinal signs. IBD can affect any part of the intestines and is classified according to the predominant cellular inflammatory infiltration. Several histological types have been recognised, which are: Lymphocytic - Plasmacytic Enteritis (LPE) and Eosinophilic Enteritis (EE).

There is no underlying cause of IBD in 75% of cases. They are thought to reflect an exaggerated or inappropriate response by the immune system to dietary, bacterial or self-antigens. IBD is a diagnosis of exclusion. Other differential diagnoses have to be investigated and ruled out before a diagnosis of IBD can be made.

Signalment

Affects the cat, dog and horse. No sex or breed or age predispositions exist.

Diagnosis

Clinical Signs

Vomiting is a very common sign in the cat, more common than diarrhoea. Where as in the dog Diarrhoeais more common and usually small intestinal. Nearly all cases of chronic small intestinal disease present with weight loss and a variable appetite. Animals often display abdominal discomfort or pain and excessive borborygmi. Lethargy, anorexia, haematemesis or haematochezia are present in more severe cases. Hypoproteinaemia or ascites may also be evident.

Laboratory Tests

Haematology

A Neutrophilia ± mild left shift will be present in LPE An Eosinophilia is not always present in EE.

Biochemistry

On biochemistry there is often a Panhypoproteinaemia, Hypocholesterolaemia and mildly elevated liver enzymes, secondary to intestinal inflammation.

Other Tests

Faecal analysis should be carried out to rule out parasitic causes such as whipworms, hookworms and Giardia. Serum folate level decreases with proximal small intestinal inflammation and serum cobalamin level decreases with distal small intestinal inflammation.

Diagnostic Imaging

Radiography

Plain radiography is used to evaluate for anatomic abnormalities. Contrast study is only valuable if there is a severe mucosal disease.

Ultrasonography

Ultrasonography may reveal mesenteric lymphadenopathy and thickening of the intestinal wall.

Histopathology

A biopsy of the intestine is required for a definitive diagnosis of IBD. A non-invasive biopsy may be taken via endoscopy. However, this limits where the samples can be taken from as the jejunum and ileum are not easily accessible. Exploratory laparotomy and full thickness biopsy may be preferred at times.

Treatment

Dietary modification

An elimination diet should be instigated. The patient should be fed strictly on a novel protein source which they have not previously been exposed to. Clinical signs should resolve within 1-2 weeks. The patient should ideally be rechallenged to demonstrate a true dietary hypersensitivity. Folate and cobalamin supplementation may be required if the levels are subnormal.

Antimicrobials

metronidazole can be given for 3-4 weeks, this may be suitable for mild to moderate cases, and especially in cats. The mucosal damage caused by IBD may decrease the animal's ability to manage intestinal flora, resulting in secondary antibiotic responsive diarrhoea (ARD) has been reported.

Immunosuppressive

This should be used if other treatments are inadequate. Prednisolonefirst and azathioprine or Cyclosporine can be given if the patient is non-responsive or unable to tolerate steroid.

Prognosis

Variable

Pathology

• Inflammatory bowel disease will result in malabsorption and in many cases, chronic diarrhoea.
• The small and/or large intestines are affected.
  • The site determines whether diarrhoea is present.

Additionally, can get extraintestinal abnormalities including cholangiohepatitis, nephritis, pancreatitis, polyarthropathy and thrombocytopenia (uncommon).

The term "inflammatory bowel disease" covers several conditions characterised by the major inflammatory cell(s) present. All have some common features: thickening of the mucosa, villus atrophy in advanced disease and significant inflammatory infiltrate in the mucosa and sometimes deeper layers.

Granulomatous enteritis

Is seen mainly in the dog but also in the cat and horse. It is idiopathic but causes granulomatous inflammation. Macrophages, giant cells, neutrophils, eosinophils, lymphocytes and plasma cells are present.

Idiopathic colitis

• Affects the dog.

Histiocytic Ulcerative Colitis

• Occurs in the dog and cat .
  • In the dog, animals less than two years old are most likely to be affected.
    • Particularly the boxer and French bulldog.
• Produces soft faeces containing mucous and blood.

Pathology

• Produces raised ulcerative nodules in the colon.
  • Due to an macrophage infiltration of the mucosa and submucosa
    • Macrophages are filled with PAS positive material.
    • Electron microscopy demonstrates macrophages to be filled with E.coli antigen.
• Accompanying lymphadenopathy.

References

Ettinger, S.J. and Feldman, E. C. (2000) Textbook of Veterinary Internal Medicine Diseases of the Dog and Cat Volume 2 (Fifth Edition) W.B. Saunders Company. Hall, E.J, Simpson, J.W. and Williams, D.A. (2005) BSAVA Manual of Canine and Feline Gastroenterology (2nd Edition) BSAVA Nelson, R.W. and Couto, C.G. (2009) Small Animal Internal Medicine (Fourth Edition) Mosby Elsevier.