Chronic diarrhea (more than three weeks duration) can be caused by GI or extra-gastrointestinal disorders, such as liver, pancreatic, or systemic diseases. Assuming extra-GI disorders are ruled out, primary GI disease can be infectious, neoplastic, toxic, or inflammatory, with noninfectious inflammatory chronic enteropathy (CE) being by far the most common.
CE can be further divided based on response to treatment, and includes diet-responsive, antibiotic-responsive, corticosteroid- or immunosuppressive-responsive, or non-responsive CE.1 It should be noted routine antibiotic treatment is discouraged due to adverse effects on the gut microbiome, risk for promoting antibiotic-resistance, and the observation most dogs relapse upon discontinuing antibiotic treatment.1 Therefore, antibiotic use should be reserved for dogs with confirmed primary infections or for those that have not responded to dietary or other therapies.2
Although these various forms of CE may have different etiologies, the clinical and histological signs often overlap, making it difficult to accurately predict how a dog might respond. Some features, including younger age, a less severe clinical scoring index (canine chronic enteropathy activity index or CCECAI), and signs consistent with large bowel disease were associated with greater likelihood of response to dietary change as the sole intervention.3 Since dietary change is the least invasive treatment, shows a fairly quick response, and is successful in a high percentage of patients, a dietary trial should be attempted in all clinically stable dogs with CE once endoparasites and enteropathogens have been ruled out or eliminated.
All dogs with CE require a nutritional assessment and a well-designed nutrition plan. The challenge to the veterinary team is identifying which dietary approach is best for an individual patient. Patient evaluation should specifically seek to identify any evidence of malnutrition and to determine which part(s) of the GI tract or associated organs are affected, as this directs selection of diets.
Key dietary features for CE
As food-responsive CE includes food allergies, as well as other food intolerance, hypoallergenic features are considered important to reduce stimulation of the GI inflammatory response. Dietary proteins are the major source of food allergens. Hypoallergenic diets may be provided as novel protein diets, or diets containing hydrolyzed proteins or purified amino acids as the sole protein sources.
Using veterinary therapeutic diets manufactured under stringent conditions minimizes the risk of cross contamination with unidentified proteins compared to over-the-counter diets. In addition to the primary protein, consideration must be given to secondary protein sources, such as from intact grains. High total digestibility is considered important, especially in the face of a compromised GI tract. Omega-3 fatty acids have a relative anti-inflammatory benefit so should be considered for inclusion.
The importance of total dietary fat is controversial, and likely depends on the patient’s body condition and underlying gastrointestinal disease. For the underweight patient in poor body condition, fat helps provide needed calories. In contrast, a patient with lymphangiectasia and protein-losing enteropathy (PLE) may require low-fat intake. For most cases of food-responsive CE, moderate fat is appropriate.
Following elimination of endoparasites, dogs with CE should be acutely transitioned to the chosen hypoallergenic diet. For many veterinarians, hydrolyzed diets are the preferred choice during this time.1 Dogs that respond to diet will begin to do so within one to two weeks. If moderate improvement is not observed within this time, consider transitioning to an alternate hypoallergenic diet, such as a different hydrolyzed diet or a homemade, novel protein diet.
In addition to the primary diet, consideration must be given to treats, flavored medications, dental care products, and foods used to give medicines as these may contain allergens. Ideally, these all should be discontinued during the initial trial, and can be added back individually following resolution of GI signs.
Dogs that respond to diet have a good long-term prognosis. Many can be transitioned to their original diet once clinical resolution is complete, or can be maintained on an appropriate hydrolyzed or hypoallergenic diet.
Non-diet-responsive CE patients will have ongoing damage to their GI tract. Therefore, dietary management will be based on provision of a highly digestible diet. Hydrolyzed diets may be beneficial due to their ease of assimilation. In some dogs, added fiber (e.g. psyllium) or a diet containing some fermentable fiber, may help correct GI dysbiosis and improve stool quality.
Protein-losing enteropathy (PLE)
Canine PLE is associated with abnormal loss of albumin through the GI mucosa, and is secondary to inflammatory CE, intestinal lymphoma, or lymphangiectasia. Diagnosing PLE can be confirmed by measuring enteric protein loss as fecal a1-proteinase inhibitor or based on histopathology.
Dietary management of PLE is based on provision of a highly digestible, low-fat diet (about 10-15 percent of diet dry matter, or about 2-2.5g/100Kcal). Although many dogs respond to this reduced fat content, some dogs require an ultra-low-fat diet (5-10 percent dry basis, or less than 1 gm/100Kcal).
Dogs with PLE are usually in severe negative energy and protein balance.4,5 Given fat is the primary driver of energy density of foods, the need for low-fat diets in PLE makes it challenging to provide adequate calories. In such patients, use of a diet containing (or supplemented with) medium chain triglycerides (MCTs), which are readily oxidized as an energy source, may be beneficial. The 8- and 10-carbon fatty acids in MCT oils are predominantly absorbed via the portal vein, bypassing the lymphatic system. It is important to note MCT oil, rather than coconut oil, must be used. Coconut oil contains longer chain fatty acids in addition to the desired 8- and 10-carbon fatty acids. As such, more fatty acids from coconut oil will be absorbed via the lymphatic system. Further, MCT oils today are tasteless and can be readily added to dog foods without adverse palatability effects. However, MCTs should not constitute more than about 30 percent of the dietary fat since they do not contain essential fatty acids, and the added fat calories will alter the nutritional balance of the overall diet.
A hypoallergenic or hydrolyzed protein diet may be beneficial in PLE as many of these dogs also have some form of inflammatory CE. Hydrolyzed protein diets tend to be lower in fat than most novel protein diets, but there are ranges in both fat and protein content among commercial therapeutic diets. Oligomeric or elemental diets providing small peptides or amino acids can be a useful alternative in the most severe or nonresponsive cases.
With severe digestive impairment and the concurrent high-energy/protein requirements affecting dogs, frequent small meals may be necessary, at least initially. Parenteral fat-soluble vitamin supplementation might be necessary in severe longstanding cases of fat malabsorption: 300 IU vitamin E; 100,000 IU vitamin A; and 10,000 IU vitamin D3 provided IM every three months is recommended.5 Low serum cobalamin is common in dogs with CE and PLE, as is hypocalcemia and hypomagnesemia. If these are documented, supplementation is appropriate. Cobalamin can be provided parenterally (50 µg/kg SQ weekly for > six weeks) or orally (cyanocobalamin at 50 µg/kg PO daily for > 12 weeks).1
Similar to food-responsive CE, PLE dogs with relatively lower CCECAI scores are more likely to respond to a low-fat diet, with responses beginning within one to three weeks.6 Partial responders may benefit from an ultra-low-fat diet. PLE dogs typically need life-long management with a low-fat diet.
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Guidelines for cobalamin supplementation and monitoring are available from the Texas A&M Gastrointestinal Laboratory. |
GI microbiota and microbial dysbiosis
Considerable evidence exists linking microbial dysbiosis as a cause or as consequence of CE in dogs.7 The microbiota plays key roles in supporting GI (and host) health, including supporting and enhancing host immune functions, and provision of short chain fatty acids (SCFAs) to feed and support the enterocytes.
CE is often associated with a shift in the microbial population from gram-positive Firmicutes (e.g. Clostridiales) to gram negative bacteria, such as Proteobacteria (e.g. Enterobacteriaceae), as well as a decrease in Clostridium hiranonis. Gut microbiota, and C. hiranonis in particular, are involved in the deconjugation and metabolism of bile acids, which are involved in inflammation and various metabolic processes. The decrease in C. hiranonis seen in canine CE results in decreased deconjugation, with reduced bile acid reabsorption and recycling, and increases in primary bile acids which may contribute to inflammation and continued diarrhea.
Dietary nutrients can have varying effects on the GI microflora, even in healthy dogs. For example, a high-protein diet increased the abundance of C. hiranonis, as well as the ratio of Firmicutes to Bacteriodetes.8 Both these changes may be beneficial in CE. Dietary fibers serving as prebiotics can alter the microbiota, as well as promote production of SCFAs.
Probiotics are theoretically useful in the management of CE. Probiotics modify the intestinal microbiota and promote host immune responses. A few studies in canine CE patients have evaluated this benefit but overall interpretation is difficult, in part, due to strain-specific effects of probiotics, differences among studies, and the concurrent use of therapeutic diets. Veterinarians should select and recommend specific probiotics that have been clinical proven for the desired benefits.
Summary
Most dogs with inflammatory CE will respond to dietary management, especially with hydrolyzed protein diets. Dogs that respond typically do so within one to two weeks. If no response is observed in that time, a second hypoallergenic diet should be tried prior to moving on to anti-inflammatory or other medical care.
Similarly, dogs with PLE often respond to diet. While a highly digestible low-fat diet may be appropriate, dogs that do not response sufficiently may need either an ultra-low-fat diet or a hydrolyzed, hypoallergenic diet. Pre- and probiotics may be advantageous in CE as most dogs with CE experience intestinal dysbiosis. As with all patients, dogs with CE that are managed via diet should be re-assessed to assure the desired response has been achieved and to consider additional dietary variables, if needed.
Dottie Laflamme, DVM, PhD, DACVIM (Nutrition) is a retired veterinary nutritionist, having worked in the research department of Ralston Purina and Nestle Purina for nearly 30 years. Her research focused on therapeutic nutrition and nutrition for aging cats and dogs.
Laura Eirmann, DVM, DACVIM (Nutrition), is currently the clinical nutritionist at the Oradell Animal Hospital in Paramus, N.J.
References
- Jergen AE, Heilmann RM. Canine chronic enteropathy—Current state-of-the-art and emerging concepts. Front Vet Sci 2022;9:923013.
- Cerquetella M, Rossi G, Suchodolski JS, et al. Proposal for rational antibacterial use in the diagnosis and treatment of dogs with chronic diarrhoea. J Small Anim Pract 2020;61:211-215.
- Allenspach K, Widland B, Grone A, Gaschen F. Chronic enteropathies in dogs: evaluation of risk factors for negative outcome. J Vet Intern Med 2007;21:700-708.
- Craven MD, Washabau RJ. Comparative pathophysiology and management of protein-losing enteropathy J Vet Intern Med. 2019;33:383–402.
- Dossin O, Lavoué R. Protein-losing enteropathies in dogs. Vet Clin N Am 2011;41:399-418.
- Myers M, Martinez SA, Shiroma JT, et al. Prospective evaluation of low-fat diet monotheraphy in dogs with presumptive protein-losing enteropathy. J Am Anim Hosp Assoc 2023;59:74-84.
- Suchodolski J. Diagnosis and interpretation of intestinal dysbiosis in dogs and cats. Vet J 2016;215:30-37.
- Li Q, Lauber C, Czarnecki-Maulden G, et al. Effects of the dietary protein and carbohydrate ratio on gut microbiomes in dogs of different body conditions. MBio 8:e01703-16.