_________ colic is when a firm mass of feed or foreign material blocks the intestine.
b. Impaction
Impaction colic – the large intestine folds upon itself and has several changes of direction (flexures) and diameter changes. These flexures and diameter shifts can be sights for impactions, where a firm mass of feed or foreign material blocks the intestine (including the cecum). Impactions can be induced by coarse feed stuff, dehydration or accumulation of foreign material like sand.
To learn more about colic read the January 2010 e-Tips article Equine Colic: Causes, Symptoms, Treatments and Prevention and watch the archived webcast Colic: Diagnosis, Treatment and Prevention by Dr. Elizabeth Carr.