b'What TypeCOLIC Is It?of ALEXANDRA BECKSTETTSHELLEY PAULSONNonstrangulating Obstructions A nonstrangulating obstruction (NSO) is a physical blockage or narrowing of some part of the gastrointestinal (GI) tract that prevents fluid and digesta from flowing through normally. These colics are by far the most commonDiana Hassel, DVM, PhD, Dipl. ACVS, ACVECC, associate professor of Equine Emergency Surgery & Critical Care at Colorado State University, in Fort Collins, estimates they make up at least 80% of colic cases in most regions of the country.Veterinarians further subcategorize these obstructions based on their location and cause, including:Feed impactions These are some of the most common NSOs and occur frequently in the large colon, particularly at the hairpin bend around the pelvic flexure and the bend into the transverse colon. Forages and fibers simply get lodged in these areas sometimes.Impactions can also occur in the ileum, which is the final part of the small intestine. Ileal impactions occur almost exclusively in adult horses in the southeastern United States, from North Carolina down to Florida over TheHorse.com|The HorseJanuary 202011Colic USE.indd 11 12/4/19 3:27 PM'