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Basics ⬇

Outline

BASICS

Definition!!navigator!!

Chronic diarrhea is defined as increased water content of feces of >2 weeks’ duration. It can be constant or intermittent.

Pathophysiology!!navigator!!

Pathophysiology depends on the underlying cause, all leading to disturbances in large intestinal function. Homeostasis between fluid absorption, fluid secretion, motility, and permeability is disturbed. The dysbiosis (abnormal bacterial flora) contributes to altered function of the GI tract.

Systems Affected!!navigator!!

  • GI—the main clinical sign is diarrhea. Recurrent colic also occurs.
  • Cardiovascular—dehydration and endotoxemia are rarely features of chronic diarrhea.
  • Musculoskeletal—weight loss is common. Ventral edema can develop.
  • Renal/urologic—renal insufficiency can occur if dehydration is present

Genetics!!navigator!!

None

Incidence/Prevalence!!navigator!!

Sporadic condition.

Geographic Distribution!!navigator!!

Worldwide

Signalment!!navigator!!

There is no reported breed, age, or sex predilection. Foals may also be affected.

Signs!!navigator!!

Historical Findings

Colic, abnormal fecal consistency, and weight loss are commonly reported. These signs may be intermittent or constant and vary in severity from mild to severe. There might be a history of antimicrobial use or management changes in the recent past.

Physical Examination Findings

  • Horses can be lethargic and show varying degrees of anorexia.
  • Diarrhea varies from cowpat to watery and is often malodorous and sometimes contains abnormal contents such as blood. Fecal appearance might be normal if the condition is intermittent.
  • Signs of colic and abdominal discomfort may be present. Abdominal wall tension may be increased and GI sounds are often hypermotile.
  • Affected horses often have decreased body condition scores, muscle wasting, and poor hair coat. Fecal staining of the hindlimbs and tail is often present and can lead to hindlimb dermatitis.
  • Cardiovascular parameters are usually normal.
  • Ventral pitting edema can occur due to hypoproteinemia

Causes!!navigator!!

There are many causes; in up to 50% of cases a cause cannot be established.

  • Dietary
    • Incorrect amount or type of feed.
    • Contaminated/spoiled feed.
    • Poor quality feed.
  • Dental abnormalities.
  • GI diseases
    • Peritonitis.
    • Abdominal abscess.
    • IBD.
    • GI neoplasia.
    • Sand impaction.
    • Chronic impaction.
    • Chronic salmonellosis.
    • GI parasitic disease.
    • Right dorsal colitis.
    • Horses <1 year of age—EPE.
    • Foals—gastric ulcers.
  • Chronic cardiac, liver, or renal disease

Risk Factors!!navigator!!

Antimicrobial use, transportation, dietary changes, surgery, and other GI disorders have been shown to cause dysbiosis. Other risk factors depend on the underlying disease.

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

Chronic cardiac, liver, or renal diseases.

CBC/Biochemistry/Urinalysis!!navigator!!

CBC

Elevated packed cell volume from dehydration can occur. White blood cell count (leukopenia with neutropenia and a left shift or leukocytosis and neutrophilia) are rare.

Biochemistry

  • Serum electrolyte concentrations are usually decreased.
  • Hypoproteinemia is common and is usually characterized by hypoalbuminemia. Globulin levels vary from low to high, depending on whether losses in the intestinal lumen occur or the production is increased (lymphoma, abscess, chronic infection).
  • Prerenal azotemia can be present if the animal is dehydrated and can result in renal insufficiency if untreated.
  • Acute-phase proteins (amyloid A, fibrinogen) can be elevated. Other abnormalities depend on the underlying disease

Urinalysis

Hypersthenuria can be present if the animal is dehydrated or decreased if renal disease is present.

Other Laboratory Tests!!navigator!!

Abdominocentesis

Can be normal or show increased protein concentration and cell count in peritonitis, lymphoma, or abdominal abscesses. With neoplasia, cytologically abnormal cells can sometimes be found.

Glucose/Xylose Absorption Test

Evaluates the capacity of the intestine to absorb glucose (and indirectly other nutrients). It is commonly abnormal in IBD, neoplasia, and EPE.

Imaging!!navigator!!

Abdominal Ultrasonography

Thickened small intestinal walls are suggestive of IBD, EPE, or lymphoma. Thickened large intestinal walls are suggestive of right dorsal colitis, neoplasia, or wall edema due to hypoproteinemia. Intestinal contents are often “fluidy.” Increased abdominal fluid is sometimes present. Masses suggestive of intra-abdominal tumors, abscesses, or enlarged lymph nodes can sometimes be imaged in the abdomen or the intestinal wall. The liver and spleen should be thoroughly evaluated for signs of disease.

Thoracic Ultrasonography and Radiographs

Can be performed to evaluate signs of thoracic lesions if a neoplastic lesion is suspected.

Echocardiography

If chronic cardiac disease is suspected.

Other Diagnostic Procedures!!navigator!!

Rectal Examination

Evaluate the walls of the intestine and check for masses suggestive of neoplasia, abscess, or enlarged lymph nodes. Chronic impactions can also be felt.

Nasogastric Intubation

To check for reflux if signs of colic are present and a GI lesion cannot be ruled out.

Fecal Sand Sedimentation

If positive, chronic sand impaction should be suspected. Fecal flotation and fecal egg count for parasites.

Fecal Culture

Salmonella culture. If EPE is suspected fecal and serum samples should be sent for testing. Bacteriologic evaluation of fecal samples is not diagnostic for dysbiosis. There is no available diagnostic test for dysbiosis.

Gastroscopy

Gastric ulcers and pyloric stenosis (particularly in foals), gastric neoplasia, and evaluate the duodenum. A duodenal and/or rectal biopsy can be submitted for histologic evaluation to test for IBD and lymphoma.

Laparoscopy or Exploratory Laparotomy

Full-thickness intestinal biopsies as a last test if no causes can be found with other diagnostics.

Pathologic Findings!!navigator!!

Dependent on the underlying cause. Large intestinal walls are often edematous and intestinal contents are excessively liquid.

Treatment ⬆ ⬇

Outline

TREATMENT

Appropriate Health Care!!navigator!!

Depending on underlying cause, some horses can be managed on the farm. As diagnostics often require specialized equipment referral to a hospital may be indicated.

Nursing Care!!navigator!!

  • IV fluid therapy using a balanced electrolyte solution should be instituted if dehydration is present. The rate of fluid administration depends on the degree of dehydration and the fluid loss through diarrhea. In severely hypokalemic horses, 20–40 mEq/L of KCl can be added to lactated Ringer's solution. IV administration of KCl should not exceed 0.5 mEq/kg/h.
  • Hindlimbs and tail should be cleaned daily. Petroleum jelly can be applied to prevent dermatitis.
  • Physical therapy (cold hosing) and bandaging of the lower limbs should be applied to decrease edema formation.
  • Fecal microbial transplantation (transfer of feces from a healthy horse via nasogastric tube) can be performed in an attempt to restore the GI microbiota

Activity!!navigator!!

Depending on the underlying condition, work has to be reduced or stopped. Diarrheic horses should be considered infectious until infectious causes have been ruled out.

Diet!!navigator!!

  • Provide free-choice good quality hay. Hay can be fed from a hay net to prevent head edema if hypoproteinemia is present.
  • Fecal consistency may normalize in some horses by replacing hay with pelleted or cube hay.
  • Higher energy feeds should be avoided unless indicated based on underlying disease.
  • Anorexic animals may benefit from forced enteral feeding or parenteral nutrition.
  • Free-choice water and a salt block should be offered at all times to allow the horse to compensate for fecal fluid losses.
  • A balanced oral electrolyte solution (35 g KCl and 70 g NaCl in 10 L of water) can be offered in addition to water to compensate for electrolyte losses.
  • Additional dietary recommendations depend on underlying disease

Client Education!!navigator!!

Salmonellosis is a potential cause of chronic diarrhea that may be zoonotic. Diagnosis can be challenging and costly.

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

Medication depends on the underlying cause. The following applies to chronic diarrhea in which no cause can be found.

Antimicrobials

The use of antimicrobial drugs in chronic diarrhea is contraindicated unless a specific infectious cause can be determined. Antimicrobials will further disrupt the colonic microbiota.

NSAIDs

Flunixin meglumine can be given (1.1 mg/kg every 12 h IV) to control signs of colic, unless right dorsal colitis is the cause.

Antidiarrhea Drugs

Di-tri-octahedral smectite (500 kg horse: 2–3 mg/kg loading dose followed by 1 mg/kg every 6–12 h PO).

Contraindications!!navigator!!

  • Metronidazole to alter the colonic microbiota is questionable.
  • There is no evidence for iodochlorhydroxyquin (clioquinol) to modify the microbiota.
  • Probiotics have questionable efficacy in horses

Precautions!!navigator!!

  • Di-tri-octahedral smectite can cause impaction if administered beyond resolution of diarrhea.
  • At a dose of 1.1 mg/kg, flunixin meglumine may be nephrotoxic in dehydrated animals

Alternative Drugs!!navigator!!

  • Any licensed NSAID can be used instead of flunixin meglumine.
  • Bismuth subsalicylate, up to 4 L/500 kg every 12 h PO or activated charcoal (1 g/kg every 24 h PO) instead of di-tri-octahedral smectite

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

Depending on disease and chosen treatment, monitoring may be frequent or periodic until resolution of clinical signs.

Prevention/Avoidance!!navigator!!

Feed, particularly hay, should be of good quality. Risk factors should be avoided if possible.

Possible Complications!!navigator!!

Chronic diarrhea can be an intermittent disease and might recur. Often it is not possible to determine the exact cause or cure the horse. Complications include hindlimb dermatitis.

Expected Course and Prognosis!!navigator!!

The course and prognosis depend on the underlying disease. In cases where a cause cannot be found, response to therapy and management changes has to be monitored. If diarrhea resolves, it might recur. Prognosis for survival is good, even if diarrhea cannot be resolved; however the prognosis for use might be guarded depending on the severity.

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

  • Hindlimb dermatitis.
  • Weight loss.
  • Chronic or recurrent colic

Age-Related Factors!!navigator!!

None

Zoonotic Potential!!navigator!!

Salmonellosis

Pregnancy/Fertility/Breeding!!navigator!!

N/A

Synonyms!!navigator!!

N/A

Abbreviations!!navigator!!

  • EPE = equine proliferative enteropathy
  • GI = gastrointestinal
  • IBD = inflammatory bowel disease
  • NSAID = nonsteroidal anti-inflammatory drug

Suggested Reading ⬆ ⬇

Mullen KR, Yasuda K, Divers TJ, Weese JS. Equine faecal microbiota transplant: current knowledge, proposed guidelines and future directions. Equine Vet Educ 2018;30:151–160.

Schoster AS, Weese JS, Guardabassi LG. Probiotic use in horses—what is the evidence for their clinical efficacy. J Vet Intern Med 2014;28:1640–1652.

Staempfli HR, Oliver OE. Chronic diarrhea and weight loss in three horses. Vet Clin North Am Equine Pract 2006;22:27–35.

Author(s) ⬆

Author: Angelika Schoster

Consulting Editors: Henry Stämpfli and Olimpo Oliver-Espinosa