Introduction

Permanent or recurrent diarrhoea is defined as chronic when it lasts longer than 3 weeks. Diarrhoea can be caused by a large variety of gastrointestinal and extra-intestinal disorders, and so a complete diagnostic work-up is recommended to obtain a definitive diagnosis so the optimal treatment can be instigated. The current approach to a patient with chronic diarrhoea should include the differentiation between extra-intestinal and primary gastrointestinal diseases. Treating extra-intestinal diseases will improve gastrointestinal signs so reducing the need for specific gastrointestinal medications. In daily clinical practice, it is not always necessary to reach a definitive diagnosis and treat every case accordingly. Symptomatic and supportive treatments without extensive diagnostic work-up are sometimes necessary, especially if there are issues with owner compliance, financial restrictions, and time pressure. Clinical, imaging and laboratory procedures including histopathology are good at diagnosing extra-intestinal and infectious or neoplastic gastrointestinal causes of canine chronic diarrhoea. However, they fail to distinguish the most common intestinal causes of canine chronic diarrhoea, namely food-, antibiotic-, and steroid-responsive enteropathy. The differentiation between these three diseases can only be achieved by observing the treatment response of an individual patient. This poses the question as to how much empirical treatment can precede diagnostic investigations, so avoiding the unnecessary use of excessive diagnostic testing.

Clinical scoring systems allow an objective assessment of the severity of a chronic enteropathy by using easy to determine parameters such as history, physical examination and results of laboratory tests. Of such indices, the canine IBD activity index (CIBDAI) is the summation of the score of six different clinical signs including attitude/activity, appetite, vomiting, stool consistency, stool frequency, and weight loss. The canine chronic enteropathy clinical activity index (CCECAI) adds the assessment of peripheral oedema, ascites, pruritus and serum albumin concentration to the CIBDAI. The CCECAI allows a better estimation of therapeutic success, with higher scores associated with an increased risk for negative outcome. The severity of the clinical score can help to decide on the necessity of further diagnostic steps. High scores with extra-intestinal clinical signs and especially panhypoproteinaemia/hypoalbuminaemia indicate the need for an immediate and more extensive diagnostic work-up.

Empirical treatment options for primary gastrointestinal disorders include a dietary change, feeding of food additives, and the application of drugs such as antiparasitics, antibiotics, pancreatic enzymes, and vitamins. Immune-modulating or immunosuppressive medication should not be used empirically but be based on objective criteria.

Diets

Dietary components especially proteins are suspected of playing a role in the pathophysiology of chronic intestinal inflammation. About 70% of dogs with chronic diarrhoea respond to a diet change alone, regardless of the initial clinical score. In order to decide the correct diet, the clinical differentiation between small and large intestinal diarrhoea is helpful. For small intestinal or mixed diarrhoea, highly digestible diets with a novel protein source or hypoallergenic, hydrolysed diets have been shown to be of benefit. Large intestinal diarrhoea responds better to diets with increased soluble and non-soluble fibre. Diets of a new protein source or hypoallergenic diets should be fed for a minimum of 10–14 days and possibly longer. In case of improvement, the diet needs to be continued for 12–14 weeks. When the patient is stable, a change of the diet to a similar commercial diet can be attempted. In cases which relapse, it is advisable to continue the diet. No improvement when a dietary change is instigated, indicates a more extensive diagnostic work-up is required, a change to another diet, or the addition of medications to the treatment.

Food Additives

For colitis, adding moderately fermentable fibre (psyllium, beet pulp) to the food has been shown to improve clinical signs, due to binding of colonic irritants and normalisation of colonic peristalsis. Additionally, fermentable fibres support the development of beneficial intestinal microbiota. The resulting increased bacterial production of short chain fatty acids is beneficial for colonic function and epithelial regeneration. The use of probiotics for the treatment of canine enteropathies is currently under research, although there is already some evidence that they are beneficial in mild disease.

Antiparasitics

Antiparasitic treatment should be based on the guidelines of International or National parasitological expert panels (e.g., Companion Animal Parasite Council (USA), European Scientific Counsel Companion Animal Parasites, Canadian Parasitology Expert Panel). To some extent, antiparasitics can be empirically used, although it is considered good clinical practice to initially perform faecal analysis on samples from three consecutive days. This approach allows a more directed treatment with better effect. Antiparasitic treatment should also include environmental control and owner education to avoid re-infection. For Giardia, a significant cause of canine chronic diarrhoea, the treatment with fenbendazole and a concurrent treatment of the animal's environment e.g., with quarternary ammonium disinfectants or hot steam, provide the optimal outcome.

Antibiotics

Patients which are not responding to a dietary change alone, but which show mild to moderate clinical signs without systemic effects, can receive empirical oral antibiotic treatment. Antibiotic-responsive enteropathies respond to the introduction of an antibiotic but relapse when the antibiotic is discontinued. Current drugs of choice are tylosin (5–25 mg/kg q24h) and metronidazole (10–20 mg/kg, q8–12h) for about 4–6 weeks. Tylosin has immunomodulatory effects and supports the establishment of supposedly probiotic enterococci. Metronidazole affects anaerobic bacteria and protozoa, and its immunomodulatory effects are based on inhibiting cell-mediated immunity and leucocyte to endothelial cell adhesion. However, it is regarded as poor clinical practice to use broad spectrum antibiotics. There is also a high risk of the development of bacterial resistance with the associated negative consequences. Failure to respond to tylosin or metronidazole should suggest further diagnostic investigations and a discontinuation of the antibiotic.

The use of enrofloxacin (5 mg/kg/day for 6–8 weeks) is currently only indicated to treat histologically proven histiocytic ulcerative colitis since it is effective against adherent and invasive E. coli causing the disease. Its empirical use should be avoided since enrofloxacin is an important antibiotic to reserve for serious disorders such as sepsis.

The use of other antibiotics should not be empirical but be based on feacal bacteriological examinations including resistance testing.

Pancreatic Enzymes

Pancreatic enzymes should only be used when exocrine pancreatic insufficiency (EPI) is proven in patients with appropriate clinical signs and pathological results of serum cTLI or faecal canine pancreatic elastase. Due to the high costs of pancreatic drugs, their empirical use should be avoided.

Vitamins

Vitamin supplementation has been suggested for dogs which are suffering from long-term maldigestion and/or malabsorption. Currently only cobalamin and folate are regularly measured in canine serum, and their use should not be empirical but based on the confirmation of a deficiency and clinical response to treatment.

Immune-Modulating and Immunosuppressive Drugs

In patients with colitis, (e.g., sulfasalazine (5-aminosalicylic acid): oral induction: 20–40 mg/kg, BID; maintenance: 10–15 mg/kg BID) has been shown to be highly effective probably due to a decrease of pro-inflammatory leucotriene production in the colonic mucosa. The drug can be used empirically, but dogs should be monitored at regular intervals for any decrease in tear production since 5-aminosalicylic acids can induce an irreversible keratoconjunctivitis sicca (dry eye).

There is a need for immunosuppressive drugs when dogs do not respond to dietary, antiparasitic and antibiotic treatments, or have mild to severe gastrointestinal signs combined with signs of systemic disease (e.g., oedema, ascites, pruritus, hypoalbuminaemia, hypocobalaminaemia). Due to the potential side-effects of currently used immunosuppressive drugs (prednisolone, azathioprine, ciclosporin and chlorambucil), their empirical use should be avoided. Before their introduction, abdominal ultrasonography and diagnostic techniques such as endoscopy or laparotomy with gastrointestinal biopsies should be performed in order to rule out neoplasia and to confirm the presence of chronic inflammation or lymphangiectasia. Also, in chronic colitis, immunosuppressive drugs should only be used if diseases such as histiocytic colitis and protothecosis are ruled out. Both conditions will worsen if the patient is treated with immunosuppressive drugs.

References

1.  Allenspach K, Wieland B, et al. Chronic enteropathies in dogs: evaluation of risk factors for negative outcome. Journal of Veterinary Internal Medicine 2007;21:700–708

2.  Jergens AE, Schreiner CA, et al. A scoring index for disease activity in canine inflammatory bowel disease. Journal of Veterinary Internal Medicine 2003;17:291–297

3.  Kilpinen S, Spillmann T, et al. Effect of tylosin on dogs with suspected tylosin-responsive diarrhoea: a placebo-controlled, randomized, double-blinded, prospective clinical trial. Acta Veterinaria Scandinavica. 2011;53:261.

4.  Parasite control guidelines:
CAPC: www.capcvet.org/capc-recommendations/ (VIN editor: link updated March 2012)
ESCCAP: www.esccap.org/index.php/fuseaction/download/lrn_file/001-esccap-guidelines-ukfinal.pdf
CPEP: www.wormsandgermsblog.com/uploads/file/CPEP%20guidelines%20ENGLISH.pdf