Influence of mechanical manipulations on the local inflammatory reaction in the equine colon.

This research investigates how various mechanical actions performed during surgery can potentially cause or exacerbate inflammation in the large intestine of horses. The focus is particularly on the equine ascending colon. The researchers conducted biopsies before, during, and after manipulating the equine colon during laparotomy in 12 horses. They found that these manipulations caused rapid inflammation in the intestinal mucosa, submucosa, and serosa, including an eosinophil response in the mucosa. They observed these changes could worsen existing inflammation in horses with large colon disease and contribute to post-operative complications.

Objective and Methodology

• The main objective of the research was to identify and quantify the type and degree of intestinal inflammation that could be induced by different mechanical manipulations during equine surgery.
• The researchers conducted a series of laparotomies on 12 horses and manipulated three segments of the left dorsal colon in different ways: enterotomy, enterotomy & mucosal irritation, and serosal irritation.
• Biopsies of the intestines were taken before, immediately following, and 30 minutes after each surgical procedure for histological examination.
• The presence of eosinophils (white blood cell subtype) was detected using Luna’s stain, while neutrophils were identified via immunohistochemical staining for calprotectin, a protein complex released by these cells during inflammation.
• In addition, samples were collected from the left dorsal colon of 14 horses involved in a jejunal ischaemia-reperfusion study. These horses underwent laparotomy either immediately after or at the end of the experiment without any prior colon manipulation.
• Both studies concluded with the euthanasia of the horses.

Results

• The researchers noted a redistribution of neutrophils and eosinophils towards the luminal surface (area of the intestine exposed to food or digested matter) and an increase of neutrophilic infiltration of the submucosa following both serosal and mucosal irritation.
• Every type of mechanical manipulation caused serosal infiltration with neutrophils.
• After laparotomy and small intestinal manipulation, an increase in eosinophilic infiltration of the mucosa was noted.

Conclusions

• The study concluded that mechanical manipulation of the intestines during surgical procedures leads to a rapid local inflammatory reaction in the mucosa, submucosa, and serosa, and includes a mucosal eosinophilic response.
• These changes could potentially intensify existing inflammation in horses suffering from large colon disease, and thus, might lead to post-operative complications and increased morbidity rates.
• The researchers recommend that an intestinal biopsy should be performed at the start of surgery to prevent incorrect interpretations caused by inflammation induced as an artifact of surgical manipulation.