Anthony T. Blikslager, DVM, PhD, DACVS
Small colon impaction is a relatively infrequent cause of colic. However, when it does occur, it can be difficult to recognize and to manage. We have noticed over the last several years that many of these cases are initiated by diarrheal disease, making the eventual diagnosis of an obstructive condition unexpected by the veterinarian.
There are other agents in each of the above categories, but these drugs can be used as examples in order to develop a treatment plan. For a horse that is actively showing signs of colic, an abbreviated physical examination (heart rate, mucous membrane color, and capillary refill time) should be performed before administering an analgesic.
There are two major reasons horses with colic may require fluid therapy: hypovolemia and endotoxemia (or sepsis). Hypovolemia results from decreased intake, loss of fluid (typically sweat or reflux), and sequestration of fluid (typically in horses that have intestinal obstruction).
Simple obstruction: an obstruction of the intestinal lumen without compromise to the blood supply. However, fluid is continually secreted into the small intestine and is not absorbed. As the intraluminal pressure increases intestinal mucosal capillaries are compressed.
Strangulation obstruction of the small intestine is frequently fatal because of simultaneous occlusion of the intestinal lumen and its blood supply, resulting in progressive necrosis of the mucosa, and development of endotoxemia. Among the more common causes of this condition are strangulating lipomas and entrapment within a natural internal opening or a mesenteric defect.
Generally, horse owners are astute at detecting signs of colic. These may include subtle not being enthusiastic about coming up from the field in the morning, not showing interest in other horses and people, or not finishing their feed. These signs should be taken seriously because in a number of occasions, these are the first signs of colic.