Definition
Chronic diarrhoea is used in dogs with diarrhoea lasting for longer than a three-week duration. It is a clinical sign that may result from primary gastrointestinal or extra-gastrointestinal diseases but is usually associated with chronic enteropathies.
Causes
In a recent publication by Volkman et al., primary gastrointestinal disease was found in 90% of the 136 dogs with chronic diarrhoea.1 Of these, inflammatory diseases were the most prevalent (71%; FRD 66% dietary responsive, 23% SRD, 11% ARD), with infectious and neoplastic diseases less frequently characterised.1 Ten percent (10%) of cases had metabolic aetiologies, including exocrine pancreatic insufficiency, endocrine, hepatic, renal and cardiac disease.
Approach
I) History and Clinical Examination
Useful information includes establishing the nature of diarrhoea, the demeanour of patient, the presence of weight loss, the presence of vomiting and associated frequency, appetite, and presence of pruritis. Dietary history should include treats, access to table scraps, and previous diet trials.
Physical examination is often unremarkable, but attention should be paid to assess for pale mucous membranes, lymphadenopathy, oedema, and joint effusion. Also thickened loops of intestine, masses or a fluid wave on abdominal palpation. The examination should also include a digital rectal exam to assess for intra- or extraluminal masses, mucosal abnormalities or blood.
II) Laboratory
Routine haematology, serum biochemistry and urinalysis are often normal but may reveal evidence of hypoalbuminemia or panhypoproteinemia, hypocholesterolemia, increased urea, anaemia or the absence of a stress leukogram. A faecal examination is recommended to screen for parasites.
Serum trypsin-like immunoreactivity and an ACTH stimulation test may be used to investigate exocrine pancreatic insufficiency and hypoadrenocorticism respectively. Determination of serum cobalamin levels may be beneficial in patient management.
III) Imaging
Abdominal ultrasound is often performed as part of the investigation in chronic diarrhoea. The overall diagnostic utility, however, was found to be low in a study, with ultrasound not making a difference in 66% of cases, providing additional benefit in only 17%.2 Sonography was shown to be most useful when abnormalities were already identified on physical examination (abdominal and rectal masses).2 Even with gastrointestinal lymphoma, 26.7% of dogs had normal sonographic findings, highlighting limitations of the modality.3
Alternatively, evaluation of the GI tract via computed tomography has also been described. Helical acquisition of 2–5 mm slices in anaesthetised dogs allowed assessment of intestinal diameter and wall thickenss.4
IV) Dietary and Antibiotic Trials
Although histopathology is perceived to be important, it cannot distinguish inflammatory bowel disease from food- and antibiotic-responsive diseases. Significant weight loss, poor body condition, anorexia, hypoalbuminemia or panhypoproteinemia, or sonographic evidence of significant infiltrative disease would indicate that endoscopy is appropriate earlier rather than proceeding with a therapeutic trial.5
Options for a dietary elimination trial include home-prepared or commercial novel protein diets, as well as hydrolysed diets. Food trials should be conducted for at least two weeks. Controversy exists between these choices as some dogs can tolerate home-prepared, single protein diets but not their commercially prepared versions. However, home-cooked diets can be unbalanced and inadequate. Choosing a novel protein may also be difficult depending on patient dietary history, and cross-reactivity between food antigens.6-8 Hydrolysed diets were found to be superior to highly digestible ones in the management of chronic enteropathy, with significantly more dogs remaining in remission at three years.9 However, concerns have been raised regarding hydrolysate diet being tolerated by most, but not all, of the dogs, sensitized to the intact compounds.10 Finally, many medications, especially OTC medications, may contain unwanted/hidden proteins.11 These should, therefore, be taken into consideration in performing an elimination diet.
Antibiotic responsive diarrhoea is hypothesised to be a result of the following factors or a combination of them: defects in the mucosal barrier, altered mucosal immune response, and dysbiosis.12 Choices of antibiotics that may be trialed include oxytetracycline, metronidazole and tylosin. Concurrent cobalamin deficiency should be managed with parenteral or oral cobalamin.
V) Biopsy
There are three means of obtaining representative tissue samples for histology: flexible endoscopy, laparoscopy, and surgery. Current recommendations are to perform upper and lower GI endoscopy as the preferred method of sampling.5 Acquisition of 6–7 adequate or 10–15 marginal tissue samples is advised for histopathological evaluation.5
Advantages of endoscopy include visualisation and biopsy of mucosal changes that cannot be seen by a serosal approach during surgery; the collection of multiple tissue biopsies per site; minimal risk of perforation and septic peritonitis, compared to surgical biopsy; and decreased morbidity to the patient. Disadvantages include limited access to the entire GI tract and the inadequacy of tissue samples that may not permit diagnosis. Recent studies have highlighted the importance of concurrent ileal biopsies in providing valuable information not always found in duodenal or colonic biopsies.13
Monitoring Management
The canine IBD activity index (CIBDAI) and the canine chronic enteropathy clinical activity index (CCECAI) help assess response to therapy. The latter consists of both objective and subjective measures. A CCECAI of >12 has been associated with negative outcomes, along with hypocobalaminemia, hypoalbuminemia and duodenal endoscopic abnormalities.14
Cases
References
1. Volkmann M, Steiner JM, Fosgate GT, Zentek J, Hartmann S, and Kohn B. Chronic diarrhea in dogs—retrospective study in 136 cases. J Vet Intern Med. 2017;31:1043–1055.
2. Leib MS, Larson MM, Grant DC, Monroe WE, Troy GC, Panciera DL, Rossmeisi JH, Werre SR. diagnostic utility of abdominal ultrasonography in dogs with chronic diarrhea. J Vet Intern Med. 2012;26:1288–1294.
3. Francis M, Lane AE, Lenard ZM. Sonographic features of gastrointestinal lymphoma in 15 dogs. J Small Anim Pract. 2013;54:468–474.
4. Hoey S, Drees R, Hetzel S. Evaluation of the gastrointestinal tract in dogs using computed tomography. Vet Radiol Ultrasound. 2013;54:25–30. doi: 10.1111/j.1740–8261.2012.01969.x.
5. Washabau RJ, Day MJ, Willard MD, Hall EJ, Jergens AE, Mansell J, Minami T, Bilzer TW. Endoscopic, biopsy, and histopathologic guidelines for the evaluation of gastrointestinal inflammation in companion animals. J Vet Intern Med. 2010;24:10–26.
6. Gaschen FP, Merchant SR. Adverse food reactions in dogs and cats. Vet Clin Small Anim. 2011;41:361–379.
7. Haroun-Díaz E, Blanca-López N, Vázquez de la Torre M, Ruano FJ, Somoza Álvarez ML, Labrador Horrillo M, Bartolomé B, Blanca M, Canto Díez G. Severe anaphylaxis due to crocodile-meat allergy exhibiting wide cross-reactivity with fish allergens. J Allergy Clin Immunol Pract. 2018;6:669–670.
8. Ballardini N, Nopp A, Hamsten C, Vetander M, Melén E, Nilsson C, Ollert M, Flohr C, Kuehn A, van Hage M. Anaphylactic reactions to novel foods: case report of a child with severe crocodile meat allergy. Pediatrics. 2017;139(4). pii: e20161404. doi: 10.1542/peds.2016–1404.
9. Mandigers PJJ, Biourge V, van den Ingh TSGAM, Ankringa N, German AJ. A randomized, open-label, positively-controlled field trial of a hydrolyzed protein diet in dogs with chronic small bowel enteropathy. J Vet Intern Med. 2010;24:1350–1357.
10. Olivry T, Bizikova P. A systematic review of the evidence of reduced allergenicity and clinical benefit of food hydrolysates in dogs with cutaneous adverse food reactions. Vet Dermatol. 2010;21:32–41.
11. Jackson HA, Hammerberg B. The clinical and immunological reaction to a flavored monthly oral heartworm prophylactic in 12 dogs with spontaneous food allergy. North American Veterinary Dermatology Forum. New Orleans (LA): American College of Veterinary Dermatology; 2002. p. 60.
12. Hall EJ. Antibiotic-responsive diarrhea in small animals. Vet Clin Small Anim. 2011:41;273–286.
13. Procoli F, Mõtsküla PF, Keyte SV, Priestnall S, Allenspach K. Comparison of histopathologic findings in duodenal and ileal endoscopic biopsies in dogs with chronic small intestinal enteropathies. J Vet Intern Med. 2013;27:268–274.
14. Allenspach K, Wieland B, Gröne A, Gaschen F. Chronic enteropathies in dogs: evaluation of risk factors for negative outcome. J Vet Intern Med. 2007;21:700–708.