Equine myenteric ganglionitis: a case of chronic intestinal pseudo-obstruction.

The research article discusses a case where a 4-year-old Standardbred mare, treated for colic signs at the New York State College of Veterinary Medicine, was found to be suffering from chronic idiopathic intestinal pseudo-obstruction (CIIP), a condition not generally associated with horses but prevalent in human literature. The mare suffered from a recurrent inflammation of her enteric nervous system, causing abnormal gastrointestinal functions and frequent bouts of small colon impactions.

Case Presentation and Initial Findings

• A 4-year-old Standardbred mare was brought in for a colic examination, revealing a small colon impaction. The condition was initially managed with medical treatment.
• However, the mare’s signs of colic recurred, necessitating an exploratory celiotomy. The operation confirmed the small colon impaction. The impaction was removed, and a tissue sample was taken for further examination.

ZHistopathological Observations via Microscopic Examination

• Microscopic analysis showed a sizeable mononuclear cell infiltration in the mare’s myenteric plexus, an extensive network of nerves in the gastrointestinal tract.
• Significant fibrosis, or the proliferation of excess fibrous connective tissue, was observed within the neuropil of the myenteric ganglia (clusters of nerve cells) and interganglionic fascicles (nerve fibre bundles).

Postoperative Developments

• The mare’s colic signs reappeared within two weeks post-operation, and she was euthanized. Samples from the proximal and distal small colon and the biopsy site were collected.
• With an intervening two weeks, the inflammatory infiltrate within the myenteric ganglia subsided. However, the preceding intraganglionic and fascicular fibrosis had increased substantially.
• There was a noticeable decrease in the number of myenteric neurons compared to age-matched controls. Among the remaining neurons, degeneration was observed, including central chromatolysis (breakdown of the cell nucleus) and cytoplasmic vacuolization (formation of cavities or vacuoles within the cell), along with many degenerate axons (nerve fibres).

Concluding Observations and Implications

• This case represents an equine instance of chronic idiopathic intestinal pseudo-obstruction (CIIP). In this case, the syndrome resulted from recurrent inflammatory damage to the mare’s enteric nervous system, altering her normal gastrointestinal functioning.
• This subsequent functional obstruction, caused by the nervous system (neurogenic), manifested as frequent bouts of small colon impactions.
• The study suggests that equine CIIP should be a consideration in the differential diagnosis of colic in horses.