Canis ISSN: 2398-2942

Antibiotic-responsive diarrhea (ARD)

Synonym(s): Bacterial overgrowth; Small Intestinal Bacterial Overgrowth (SIBO

Contributor(s): James Simpson, Ken Harkin, Marge Chandler

Introduction

  • In contrast to dogs, the syndrome of SIBO in humans is relatively well defined, and is characterized by a variety of clinical features, including macrocytic anemia, steatorrhea, and weight loss.
  • Previously defined in the dog as >(10*5) colony-forming units (CFU)/ml of proximal small intestinal fluid following aerobic and anaerobic culture. However normal data is now disputed, consequently there are currently no diagnostic tests which reliably detect this condition; hence the name change to antibiotic-responsive diarrhea (ARD) which fits the clinical presentation of suspect cases and reflects the emphasis on the host-bacteria interactions and immunopathologic effects of enteric bacteria on disease.
  • Cause: IgA deficiency, achlorhydria, inflammatory bowel disease (IBD), exocrine pancreatic insufficiency (EPI), stagnant loop, ileus.
  • Signs: variable combination of chronic diarrhea and weight loss; appetite may be increased, normal or decreased.
  • Diagnosis: previous diagnostic test: elevated serum folate and reduced cobalamin levels. Limitations in the diagnostic utility of measurement of serum folate and cobalamin concentrations for diagnosing SIBO in dogs shown in a study which failed to show a correlation between bacterial counts and serum vitamin concentrations. The diagnostic utility of these tests is further compromised because serum folate concentrations can be normal or decreased in dogs with SIBO due to decreased absorption secondary to proximal small intestinal pathology, whereas serum cobalamin concentrations can be decreased by diseases other than SIBO, including exocrine pancreatic insufficiency and severe mucosal disease in the ileum.
  • Previously thought that the definitive diagnosis was by quantitative culture of proximal intestinal fluid. Now considered difficult to interpret as this technique has major limitations, and there is variability between different studies.
  • Treatment: depends on resolving any underlying diseases; if none identified use antibiotics and dietary management.
  • Prognosis: reasonable with appropriate therapy, depending upon underlying disease.

Pathogenesis

Etiology

Predisposing factors

General
  • Decreased gastric acid secretion.
  • Intestinal hypomotility.
  • Immunodeficiency (IgA especially).

Specific

  • Exocrine pancreatic insufficiency Exocrine pancreatic insufficiency (70% have SIBO/ARD).
  • Intestinal surgery, especially if ileocolic valve is removed or >85% of intestine is removed (short bowel syndrome).
  • Stagnant loop - ileus - hypomotility.

Pathophysiology

Bacterial metabolism of intraluminal contents
  • Excess numbers of intraluminal bacteria → production of metabolites, eg deconjugated bile salts, hydroxylated fatty acids → intestinal mucosal damage → secretion of fluid into intestine → diarrhea → also brush border damage → decreased disaccharide activity → malabsorption → chronic diarrhea and weight loss.
  • Abnormal host-bacteria interactions and immunopathologic effects of enteric bacteria on disease.

Timecourse

  • Variable.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Westermarck E, Skrzypczak T, Harmoinen J et al (2005) Tylosin-responsive chronic diarrhea in dogs. J Vet Intern Med 19, 177-186 PubMed.
  • German A J, Day M J, Ruaux C G et al (2003) Comparison of direct and indirect tests for small intestinal bacterial overgrowth and antibiotic-responsive diarrhea in dogs. J Vet Intern Med 17, 33-43 PubMed.
  • Bissett S A et al (1997) Breath hydrogen testing in small animal practice. Comp Cont Ed Prac Vet 19 (8), 916-928 VetMedResource.
  • Rutgers H C et al (1995) Small intestinal bacterial overgrowth in dogs with chronic intestinal disease. JAVMA 206, 187-183 PubMed.
  • Davenport D J, Ching R J W, Hunt J H, Bruyette D S, Gross K L (1994) The effect of dietary levels of folate and cobalamin on the serum concentration of folate and cobalamin in the dog. J Nut 124 (Suppl), 2559S-2562S PubMed.
  • Simpson K W, Batt R M, Jones D & Morton D B (1990) Effects of exocrine pancreatic insufficiency and replacement treatment on the bacterial flora of the duodenum of the dog. Am J Vet Res 51 (2), 203-206 PubMed.

Other sources of information

  • Hall E J, German A J (2010)diseases of the small intestine.In:Textbook of Veterinary Internal Medicine, 7th edn. Ettinger S J & Feldman E C (eds). Saunders Elsevier, St Louis, Mo. pp 1526-1572.


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