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Basics ⬇

Outline

BASICS

Definition!!navigator!!

Idiopathic colitis/typhlitis is a severe inflammatory condition of the large intestine with unknown etiology.

Pathophysiology!!navigator!!

It is likely a consequence of disturbed microbiota, upsetting homeostasis of absorption, secretion, permeability, and motility. This results in net colonic fluid accumulation, intestinal wall inflammation, systemic electrolyte imbalances, protein loss, and disturbance of the coagulation cascade, resulting in diarrhea and systemic clinical signs.

Systems Affected!!navigator!!

GI

The main clinical sign is diarrhea. Varying signs of colic and ileus may be present.

Cardiovascular

Varying severity of dehydration, endotoxemia, and cardiovascular shock. Systemic and local thromboembolic events, including venous thrombosis of catheter sites, can occur.

Musculoskeletal

Laminitis may develop. Peripheral edema occurs with severe hypoproteinemia.

Respiratory

Septic emboli leading to pulmonary abscess formation may occur.

Renal

Acute renal insufficiency due to dehydration can occur.

Genetics!!navigator!!

N/A

Incidence/Prevalence!!navigator!!

Sporadic condition. If outbreaks occur, an infectious agent should be suspected.

Geographic Distribution!!navigator!!

Worldwide

Signalment!!navigator!!

There is no reported breed, age, or sex predilection. Foals as young as 24 h of age may be affected.

Signs!!navigator!!

Historical Findings

Animals may be presented before the development of diarrhea with colic, abdominal distention, depression, anorexia, and pyrexia. Recent antibiotic use, change of feeding management, recent deworming, transport, surgery, or other management changes (stressors) may be reported.

Physical Examination Findings

  • Diarrhea is present in most cases and may vary from cowpat consistency to profuse and watery to hemorrhagic
  • Dehydration, fever, and tachycardia are common
  • GI sounds may be hypermotile or hypomotile
  • Signs of endotoxemia may be present
  • Marked intestinal distention, especially in peracute cases, may be seen and cause colic. Gastric reflux or cessation of fecal passage can occur due to ileus
  • Ventral edema may be present secondary to hypoproteinemia

Causes!!navigator!!

Disturbance of the colonic microbiota; inciting agents that have yet to be identified or are missed owing to low diagnostic test sensitivity.

Risk Factors!!navigator!!

Antimicrobial use, transportation, dietary changes, surgery, and other GI disorders.

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Salmonellosis
  • Clostridium difficile colitis
  • Clostridium perfringens colitis
  • Potomac horse fever
  • Cyathostomiasis
  • NSAID-induced colitis
  • Cantharidin toxicosis
  • Coronavirus-associated diarrhea
  • Chronic sand impaction
  • Foals—rotavirus diarrhea
  • Gastric ulcers
  • Cryptosporidia
  • Strongyloides westeri
  • Sepsis

CBC/Biochemistry/Urinalysis!!navigator!!

CBC

  • Elevated PCV from dehydration and splenic contraction is common
  • Serum protein levels may be increased due to hemoconcentration but hypoproteinemia due to protein loss into the GI wall and lumen is more frequent
  • Leukopenia with neutropenia and a left shift is often present early. Toxic changes may be present in neutrophils. At later stages of disease or in milder cases, a leukocytosis and neutrophilia may be present

Biochemistry

  • Serum sodium, chloride, and calcium concentrations are typically decreased, potassium concentrations are variable, likely due to electrolyte loss into the intestinal lumen
  • Prerenal azotemia is common and can result in renal insufficiency
  • Blood lactate is often elevated and severity can be a prognostic indicator
  • Acute-phase proteins serum amyloid A and fibrinogen are often elevated

Urinalysis

Increased urine specific gravity due to dehydration.

Other Laboratory Tests!!navigator!!

Acid–base assessment—marked metabolic acidosis due to electrolyte derangements and hyperlactatemia can develop.

Imaging!!navigator!!

Abdominal Ultrasonography

The large colon is fluid filled, walls are edematous, and excess motility occurs.

Other Diagnostic Procedures!!navigator!!

Diagnosis is based on exclusion of other causes; appropriate samples should be submitted to rule out the common causes of colitis.

Pathologic Findings!!navigator!!

Marked exfoliation of colonic and cecal mucosal epithelial cells and hemorrhagic colitis–typhlitis, with thrombosis of the intestinal mucosal capillaries, are common.

Treatment ⬆ ⬇

Outline

TREATMENT

Appropriate Health Care!!navigator!!

This condition is best managed with intensive inpatient care. Cases with mild diarrhea and adequate hydration may be treated at the farm but require close monitoring as a rapid deterioration may occur.

Nursing Care!!navigator!!

  • IV fluid therapy using a balanced electrolyte solution (e.g. LRS) is often mandatory. The rate of fluid administration depends on the degree of dehydration and the estimated fluid loss through diarrhea. The use of 2 large-bore catheters in separate veins may help deliver a large volume of fluid for the rapid correction of fluid deficits in severely dehydrated horses. After correction of dehydration, IV administration of maintenance fluids (50–100 mL/kg/day) plus the estimated fluid loss through diarrhea should be continued. Hydration status should be assessed frequently because affected animals may become dehydrated even in the presence of fluid therapy
  • Mild to moderate cases of metabolic acidosis typically resolve with fluid therapy. In severely hypokalemic horses, 20–40 mEq/L of KCl can be added to LRS or saline. IV administration of KCl should not exceed 0.5 mEq/kg/h
  • An oral electrolyte solution containing 35 g KCl and 70 g NaCl in 10 L of water should be provided, along with clean, fresh drinking water and a salt block
  • IV administration of hypertonic saline (4–6 mL/kg of 5–7.5% NaCl) may be indicated in severely dehydrated animals. It is essential that isotonic fluid therapy follows the use of hypertonic saline
  • Fecal microbial transplantation can be performed to re-establish a normal GI microbiota. Probiotics are likely not effective
  • Owing to the high incidence of venous thrombosis in colitis, the catheter site should be monitored frequently
  • If distal limb edema develops due to hypoproteinemia, leg wraps should be applied and changed daily
  • Deep bedding should be provided if there are any signs of laminitis. Hooves should be iced for 72 h

Activity!!navigator!!

Owing to the need for continuous IV fluid therapy in most cases, stall confinement is required. Diarrheic horses should be considered infectious.

Diet!!navigator!!

  • Affected horses should be provided with free-choice hay. It is recommended to feed hay in a hay net to prevent severe facial and head edema
  • Higher energy feeds can also be provided, but should be introduced slowly and fed in small amounts
  • Anorexic animals may benefit from forced enteral feeding. Partial or total parenteral nutrition may be indicated

Client Education!!navigator!!

Inform clients that colitis is a potentially life-threatening condition, often associated with development of secondary problems, such as laminitis and jugular vein thrombosis. In multi-horse environments, it is important to explain the risk of infection to other animals and humans (salmonellosis).

Surgical Considerations!!navigator!!

N/A

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

Antimicrobial Agents

  • The use of antimicrobial drugs is controversial
  • Metronidazole 15–25 mg/kg every 6–8 h should be given if clostridial involvement cannot be ruled out
  • Administration of broad-spectrum antibiotics to severely neutropenic patients has been suggested to prevent sepsis. Additional disturbance of the microbiota occurs with antimicrobial therapy and can worsen diarrhea. Options include ceftiofur sodium 2–5 mg/kg IV or IM every 12 h, trimethoprim–sulfamethoxazole 24 mg/kg IV every 12 h or gentamicin 6.6 mg/kg daily in combination with sodium penicillin (22 000–30 000 IU/kg every 6 h); the last combination should only be used if renal function is normal and fluid deficits are addressed
  • Antimicrobial therapy should be discontinued when clinical and laboratory values improve

Flunixin Meglumine

A dose of 0.25–0.5 mg/kg every 8 h can be used for antiendotoxic effects. A higher dosage (1.1 mg/kg) is necessary for analgesia.

Endotoxin Binding Drugs

Administration of hyperimmune serum (hyperimmunized to Escherichia coli J5 strain and/or polymyxin B (6000 IU/kg every 6–8 h IV) to moderate the effects of endotoxemia.

Colloidal Therapy

Colloidal solutions (e.g. whole blood, plasma, hetastarch) can be used to maintain the fluid in the vascular space. Colloids should be considered when plasma proteins are less than 4 g/dL (40 g/L). Plasma provides the additional benefit of anticoagulants, and procoagulant substances.

Antidiarrhea Drugs

Di-tri-octahedral smectite (loading dose 3 g/kg PO then 0.5–3 g/kg every 6–8 h PO)—can cause impaction if administered beyond resolution of diarrhea.

Laminitis Treatment

See chapter Laminitis.

Contraindications!!navigator!!

See Pregnancy/Fertility/Breeding.

Precautions!!navigator!!

At a dose of 1.1 mg/kg, flunixin meglumine may be nephrotoxic in dehydrated animals.

Possible Interactions!!navigator!!

None

Alternative Drugs!!navigator!!

N/A

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Patients should be monitored frequently. Initially, PCV and total plasma protein levels should be evaluated at least daily
  • If azotemia was present, this should be reevaluated after rehydration to ensure it was prerenal
  • Plasma electrolytes should be monitored to determine whether supplementation with potassium and calcium is required
  • The IV catheter site should be monitored frequently for signs of thrombophlebitis
  • The feet should be checked frequently for evidence of laminitis

Prevention/Avoidance!!navigator!!

None

Possible Complications!!navigator!!

  • Endotoxemia
  • Laminitis
  • Jugular vein thrombosis
  • Renal failure
  • Pulmonary abscessation

Expected Course and Prognosis!!navigator!!

This disease often has a very fulminant character and horses may succumb to it within 8–24 h. There is a wide variety in the severity. Mortality rates have been reported in the range 10–40%.

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

  • Laminitis
  • Venous thrombosis

Age-Related Factors!!navigator!!

None

Zoonotic Potential!!navigator!!

All affected horses should be treated as zoonotic until shown to be negative for Salmonella spp. and C. difficile.

Pregnancy/Fertility/Breeding!!navigator!!

Metronidazole should not be administered to pregnant mares as it is teratogenic. An increased risk of abortion may be present due to endotoxemia and hypovolemic shock.

Synonyms!!navigator!!

Undifferentiated colitis, acute diarrhea. Old—colitis X.

Abbreviations!!navigator!!

  • GI = gastrointestinal
  • LRS = lactated Ringer's solution
  • NSAID = nonsteroidal anti-inflammatory drug
  • PCV = packed cell volume

Internet Resources!!navigator!!

ACVIM Fact Sheet: Colitis in Adult Horses. http://www.acvim.org/Portals/0/PDF/Animal%20Owner%20Fact%20Sheets/LAIM/Colitis%20in%20Adult%20Horses.pdf

Suggested Reading ⬆ ⬇

Shaw SD, Stäempfli HR. Diagnosis and treatment of undifferentiated and infectious diarrhea in the adult horse. Vet Clin North Am Equine Pract 2018;34:39–53.

Author(s) ⬆

Author: Angelika Schoster

Consulting Editors: Henry Stämpfli and Olimpo Oliver-Espinosa

Acknowledgment: The author acknowledges the prior contribution of Olimpo Oliver-Espinosa and Henry Stämpfli.