How I Evaluate the Chronic Colic

Take Home Message  

Evaluation of the horse that presents for chronic colic is a diagnostic and client management  challenge to the clinician and potential source of frustration to the horse owner. A stepwise  approach to clinical investigation and the setting of realistic expectations is paramount to  reaching the best possible outcome for all involved parties.  

Introduction  

The horse that exhibits chronic, intermittent, colic creates a situation fraught with difficulties for  both the owner and veterinarian. The owner may have sought many opinions, both lay and professional, prior to presentation. Considerable financial resources may have already been  expended in attempting to secure a diagnosis, or in the absence of a diagnosis, a cure. Seemingly contradictory advice may have been given and followed resulting in further frustration for the owner. Diagnostic techniques in the horse vary greatly in their utility, cost and degree of  invasiveness. Many factors have been incriminated experimentally and clinically in the  precipitation of a colic episode, with great variation occurring between studies.¹ 

Evaluation  

History  

Frequency and duration of colic episodes will vary. Horses may have repeated colic episodes of  varying magnitude on a seemingly repeatable or random schedule. Careful examination of the history may uncover seemingly unrelated events that may act as ‘triggers’ that initiate the colic  episode. These may include a feed change (quantity, quality or frequency), administration of  medications, exercise changes, environmental changes, transport, social stress (in contact horse,  owner), or estrous activity.  

Physical Examination  

The overall physical condition of the horse gives insight into management and underlying medical conditions that may be contributing to the signs of colic.  

Loss of weight or inability to gain weight when presented with a high quality diet that is readily consumed in adequate amounts suggests malabsorption, maldigestion or catabolism.

Malabsorption and maldigestion result from inflammatory or infiltrative disease processes  affecting the intestinal wall. Catabolism results from the energy demands of an underlying disease process that may be infectious, inflammatory, or neoplastic. Chronic pain can raise stress  hormone levels leading to catabolism. Underlying metabolic derangements may be suggested by body conformation (e.g. Cushing’s disease, insulin resistance).  

Diarrhea  

The presence of diarrhea may indicate an infectious, infiltrative or inflammatory disease  processes causing the colic signs. Chronic Salmonellosis with persistent inflammation, even if regional, may lead to intermittent abdominal pain. Medication usage (antimicrobials, NSAIDs)  may cause colonic inflammation and secondary abdominal pain. Inflammatory bowel disease (IBD) may lead to chronic or intermittent diarrhea with or without concurrent abdominal pain.  

Rectal Examination  

The disposition and content of the abdominal viscera, intestinal wall characteristics, presence of extraneous masses, or alterations in the shape, location and consistency of the parenchymous organs may be detected on rectal examination. Chronic displacement or entrapment of the  intestines may be palpable, and fecal impactions at the pelvic flexure, small colon and cecal base  may be detected. Intestinal wall thickness may suggest infiltrative disease, or in the case of the  ileum muscular hypertrophy. Serosal surfaces can be assessed for roughening which is suggestive of a septic peritonitis.  

Ultrasonography  

Disposition and size of the intestinal tract and organs within the abdominal cavity as well as their  consistency, location and ultrasonographic architecture can be determined. Intestinal wall  thickness can be objectively measured. The size of the stomach can be estimated. The location,  amount, and consistency of peritoneal fluid may be determined aiding performance of  abdominocentesis. Intestinal contents can be judged for propulsive activity and consistency.  

Gastroscopy  

Gastric ulceration when present can be a source of discomfort and chronic colic in affected  horses. Gastric impactions, gastric masses and the majority of the stomach from cardia to outflow tract down to the pyloric sphincter can be evaluated with a 3 meter scope. It should be  noted that the absence of gastric ulceration does not preclude ulceration in more distal areas of the intestinal tract e.g. right dorsal colon, cecum.  

Laboratory Evaluation  

Complete Blood Count and Serum Chemistry  

The presence of an inflammatory leukogram may suggest abdominal abscessation, peritonitis or adhesion formation. Disturbances in specific serum chemistry values may reflect inflammation, dysfunction or obstructive lesions of the liver (SDH, AST, GGT, bile acids, hypoalbuminemia)  or kidney (creatinine, BUN, hypoalbuminemia).  [...]