Colic, defined as any abdominal pain, is one of the most common causes of presentation for veterinary treatment, as well as death in horses.
Colic is a broad term for a variety of conditions that cause the horse to exhibit clinical signs of abdominal pain. Consequently, it is used to refer to conditions of widely varying etiologies and severity. To understand these etiologies, make a diagnosis, and initiate appropriate treatments, veterinarians must first appreciate the clinically relevant aspects of equine GI anatomy, the physiologic processes involved in movement of ingesta and fluid along the GI tract, and the extreme sensitivity of the horse to the deleterious effects of bacterial endotoxin that normally exists within the lumen of the intestine.
- Verminous arteritis - Strongylus spp and Anoplocephala spp
- Sand - sandy pastures
- Pelvic flexure impaction - caused by impacted fibre
- Spasmodic colic - wind-sucking, and certain bloat-producing grasses (e.g. lucerne)
- Intussusception, intestinal volvulus
- Right dorsal colitis
- Idiopathic focal eosinophilic enteritis
- Gastric impaction, gastric ulceration.
- Viral diseases
- Drug reactions
- - Diaphragmatic hernia with secondary small intestinal strangulation
- - retained meconium, atresia coli, meconium retention, uroperitoneum, gastroduodenal ulcers, small-intestinal intussusception, nonstrangulating infarction, foreign body obstruction
- Aged horses
- - pedunculated lipoma, mesocolic rupture
Clinically affected horses often present with a variety of symptoms which may include repeated pawing with a front foot, looking back at the flank region, repeatedly raising a rear leg or kicking at the abdomen, lying down, sweating, stretching out as if to urinate, straining to defecate, distention of the abdomen, loss of appetite, depression, and decreased number of bowel movements.
Passing of a nasogastric tube may alleviate gastric bloat or obstructions involving the small intestine. If fluid reflux occurs, the volume and color of the fluid should be noted.
Intestinal sounds associated with episodes of pain may indicate an intraluminal obstruction (eg, impaction, enterolith). Gas sounds may indicate ileus or distention of a viscus. Fluid sounds may indicate impending diarrhea associated with colitis. A complete lack of sounds is usually associated with adynamic ileus or ischemia. Percussion will assist in identifying a grossly distended segment of intestine (cecum on right, colon on left) that may need to be trocarized. The respiratory rate may be increased due to fever, pain, acidosis, or an underlying respiratory problem. Diaphragmatic hernia is also a possible cause of colic.
A rectal examination may allow palpation of the abdominal contents and possibly reveal abnormalities in various structures such as the cranial mesenteric artery, cecal base and ventral cecal band, duodenum, bladder, peritoneal surface, inguinal rings in stallions and geldings or the ovaries and uterus in mares, pelvic flexure, spleen, and left kidney. The intestine should be palpated for size, consistency of contents (gas, fluid, or impacted ingesta), distention, edematous walls, and pain on palpation.
A sample of peritoneal fluid (obtained via paracentesis performed aseptically on midline) often reflects the degree of intestinal damage. The color, cell count and differential, and total protein concentration are often elevated. Normal peritoneal fluid is clear to yellow, contains <5,000 WBC/µL, most of which are mononuclear cells, and <2.5 g of protein/dL.
Blood tests may reveal dehydration, as evidence by an hematocrit > 0.5 l/l. Additionally, elevated levels of blood lactate concentration > 4 mmol/l indicates a guarded prognosis (caution in interpretation with ponies and miniature horses, where elevated levels may be normal). Other values such as serum amyloid A are often elevated in colic horses.
Transrectal or transcutaneous ultrasonography may assist in the differentiation of causes. In ponies and foals, radiography may be an additional diagnostic imaging modality to consider.
A differential diagnoses include other causes of stiff-gaited stance such as laminitis.
Passage of a nasogastric tube and drenching with mineral oil (up to 4 L once or twice daily) may alleviate bloat, impactions or sand.
In cases of suspected larval colic, larvicidal deworming is indicated. Drugs such as ivermectin, moxidectin and fenbendazole are commonly employed.
Fluid therapy given per os or intravenous is indicated in severe cases.
Intravenous fluids are given in cases of dehydration at volumes of 8 - 10 L, given over 1 - 2 hours. In severe cases, hypertonic saline (7% NaCl) may be given to rapidly increase plasma volume. Depending on the cause of colic, IV fluids may be needed for several days until intestinal function has returned, electrolyte concentrations are balanced, and the horse can maintain its fluid needs by drinking. Under such circumstances, the daily IV fluid requirements may range from 30 to 100 L.
Surgery usually is indicated in cases where severe abdominal pain is nonresponsive to analgesic therapy. This requires specialist intervention and may be costly, and have a relatively high risk of failure if large sections of intestine are compromised.
- University of Edinburgh
- Merck Veterinary Manual
- Sasani F et al (2013) A report of left dorsal displacement of the large colon in a tropical horse. Asian Pac J Trop Biomed 3(4):325-329
- Bird AR et al (2012) The clinical and pathological features of gastric impaction in twelve horses. Equine Vet J Suppl 44(43):105-110
- White NA. (1990) Epidemiology and etiology of colic. In: White NA, ed. The equine acute abdomen. Philadelphia: Lea and Febiger
- Donnellan CM et al (2012) Comparison of glycopyrrolate and atropine in ameliorating the adverse effects of imidocarb dipropionate in horses. Equine Vet J Dec 19
- Röcken M et al (2013) Thoracoscopic Diaphragmatic Hernia Repair in a Warmblood Mare. Vet Surg Apr 25
- Donawick WJ, Ramberg CF Jr., Topkis GA. (1982) Absorption and secretion of water and electrolytes by normal and obstructed ileum of ponies, in Proceedings. Equine Colic Research Symposium
- Sullins KE, Stashak TS, Mero KN. (1985) Pathologic changes associated with induced small intestinal strangulation obstruction and nonstrangulating infarction in horses. Am J Vet Res 46:913–916
- Dabareiner RM, White NA, Donaldson LL. (2001) Effects of intraluminal distention and decompression on microvascular permeability and hemodynamics of the equine jejunum. Am J Vet Res 62:225–236
- Cavalleri JM et al (2013) Examination of horses with acute colic - clinical pathology and diagnostic imaging. Tierarztl Prax Ausg G Grosstiere Nutztiere 41(2):124-134
- Dunkel B et al (2013) Blood lactate concentrations in ponies and miniature horses with gastrointestinal disease. Equine Vet J Jan 10
- Pihl TH et al (2013) Serum amyloid A and haptoglobin concentrations in serum and peritoneal fluid of healthy horses and horses with acute abdominal pain. Vet Clin Pathol Apr 11
- Boesch JM (2013) Anesthesia for the horse with colic. Vet Clin North Am Equine Pract 29(1):193-214