Inflammatory Bowel Disease
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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, including 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 Diarrhoea is 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 ± a 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.
Pathology
The term inflammatory bowel disease covers several conditions characterised by the major inflammatory cells present. all have some common features and these includethickening of the mucosa, villus atrophy in advanced disease and significant inflammatory infiltrate in the mucosa and sometimes deeper layers. Increased numbers of plasma cells, lymphocytes, eosinophils, and neutrophils in the lamina propria are seen in IBD.
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. Prednisolone first and azathioprine or Cyclosporine can be given if the patient is non-responsive or unable to tolerate steroid.
Prognosis
Variable
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.