Muscle thickness and neuron density in the caecum of horses with chronic recurrent caecal impaction.

This research article investigates the link between the thickness of caecal smooth muscle and the density of neurons in the myenteric plexus in horses suffering from chronic recurrent caecal impaction, as compared to healthy horses. The study found that horses with this condition had thicker caecal muscles and lower neuron densities.

Study Objectives

• This research aimed to test the theory that the smooth muscle layers of the caecum (a part of the horse’s gut) would be thinner, and the neuronal density of the myenteric plexus (a network of neurons controlling gut motion) higher, in healthy horses than those suffering from chronic recurrent caecal impaction— a condition that causes an obstruction in the horse’s intestine.

Experiment Methodology

• The study involved four control horses and 18 horses with chronic recurrent caecal impaction. All of them were euthanized for the study.
• A total of seven tissue samples were collected from each horse at different locations within the caecum.
• In 12 of the horses with chronic recurrent caecal impaction, surgery was carried out. One tissue sample from each of these horses was taken during surgery, specifically from the cranial region of the caecal base and close to the caecocolic orifice.

Findings

• The thickness of the circular muscle layer of every region of the caecum was found significantly increased in the horses with chronic recurrent caecal impaction as compared to the equivalent locations in the healthy horses.
• While the longitudinal muscle layer was notably thicker only in the cranial and caudal base of the caecum and in the dorsal region of the caecal body.
• Furthermore, it was found that the linear neuron densities in all the base regions of the caecum and two body regions, the top and bottom body region, were significantly lower in horses with the chronic recurrent condition compared to the normal horses.

Conclusion

• This data suggests that the circular muscle layer in all regions of the caecum became hypertrophied (thickened), possibly due to chronic disorganized hypercontractility arising from neuron deficiency in the myenteric plexus of the caecal base.