Causes of colic and types requiring surgical intervention.

The migration of strongyle larvae is the most common or basic underlying cause of colic in the horse. Disease conditions producing symptoms of colic occur in all sections of the intestinal tract and consist of impactions, torsions, herniations and foreign bodies. Colic also occurs as a result of pre- and post-partum diseases such as torsion of the uterus, haemorrhage, rupture and inversion of the uterus. In general, lesions resulting in circulatory obstruction are the types requiring surgical intervention. There are six general types of small intestine obstruction that lend themselves to surgical treatment; namely, volvulus, herniations, intussusceptions, stenosis of the lumen of the bowel by external bands or by foreign bodies and chronic inflammatory lesions. The large intestine is not subject to the variety of obstructive lesions found in the small intestine. Impactions count for a large percentage of the obstructions seen. A standing laparotomy for diagnostic purposes may be indicated. Small colon impactions are readily treated by standing laparotomy. Enteroliths are of very common occurrence in some areas of the country; they often result in rupture of the colon. Torsions of the colon produce septic shock very rapidly. The left dorsal colon moving medially or laterally and ventrally initiates the torsion. Clockwise rotation is most common. Massive intravenous therapy is needed to maintain hydration. Ventral midline laparotomy gives best access. Surgery must be performed very early to avoid massive tissue necrosis. Survival rate is 30 percent or less. The small colon is also capable of rotation and volvulus, and of strangulation in the umbilical or inguinal ring.