Megacolon in two related Clydesdale foals.

This study examines two cases of a condition known as megacolon in two related Clydesdale foal horses. The condition, characterized by an abnormal enlargement of the colon, resulted in chronic intestinal obstruction in the foals when they were four and nine months old, respectively.

Background and Purpose

• The research discusses the phenomenon of “Megacolon”, a condition where there is a substantial dilation of the colon. It can either be congenital, present from birth, or acquired, through a chronic mechanical obstructive process or a degeneration of pre-existing myenteric ganglion cells.
• In this specific study, the researchers focus on the cases of two related Clydesdale foals, that presented symptoms of chronic intestinal obstruction at the ages of four and nine months, respectively. The main objective was to study how this condition manifests in horses, particularly in Clydesdale foals.

Case Examinations

• The first case revolves around a four-month-old Clydesdale colt that was brought to the University of Sydney’s Rural Veterinary Centre. The horse had been showing signs of lethargy and abdominal distension for a month.
• Through a process of abdominal paracentesis, the researchers identified predominantly red blood cells and polymorphonuclear leucocytes, including some presenting degenerative changes. This evidence suggested a compromised large intestinal wall, which led them to diagnose a large intestinal obstruction. This case ultimately resulted in performing an exploratory laparotomy.
• The second case involves a nine-month-old Clydesdale filly referred to the same center with symptoms of abdominal distension and loss of appetite. After multiple examinations, the same prognosis was reached: a large intestinal obstruction.
• In both cases, anesthesia was induced and maintained to carry out a ventral midline laparotomy. During surgery, they found similar abnormalities in both the foals: massively distended, congested, and impacted dorsal colons.

Query into Ancestry

• The researchers also looked into the pedigree of both foals, finding out that they had a common sire and that certain stallions regularly appeared in their ancestry. Despite similarities in pedigree, the study does not provide a definitive link between the genetic makeup of these horses and the occurrence of the medical condition.

Necropsy and Observations

• Necropsies were performed on both foals shortly after their death and identified that the grotesque changes were restricted to the left and right dorsal colons which were hugely distended due to fecal impaction.
• In both cases, the mucosa of the left dorsal colon was congested, with the blood staining the adjacent impacted contents. The intestinal wall was intact but so thinly stretched that it could easily rupture.

It’s important to note that the study is limited to these two Clydesdale foals and their specific medical circumstances. Further research is needed to understand more holistic aspects of equine megacolon, such as potential risk factors, genetic predispositions, and prevention strategies.