Diarrhea is a common symptom in the horse that can be caused by a number of different factors. Many diarrheas are caused by noninfectious or noninflammatory reasons and these horses have a change in their stools but continue to eat, drink, act normal and have no fever, ...more. The list of differentials in foals with colitis is a bit different as is the treatment so it is covered in a separate topic, ...more

This article concerns itself with adult horses that have an acute onset of severe diarrhea and act sick. Note this can be an emergency situration as shock may be developing and you should call your veterinarian now. Systemic illness and diarrhea and most often caused by inflammation of the large bowel and called colitis. Colitis can be caused by infections or toxins, usually acting as a chemical irritant. The result is diarrhea which may be accompanied by fever, depression, colic, and if severe shock and death.

Usually it is recommended to diagnose a disease before you begin treatement but severe colitis does not give you the time for an exact diagnosis. Shock and/or founder may be rapidly developing. This article discusses the initial evaluation to determine severity and emergency treatment to ward off the possible life threatening complications. Also discussed are the causes of the serious complications and then goes over the various differential diagnosis and important diagnostic steps. Links to articles on the specific complications and diseases are provided as are summaries of the most current research and veterinary papers published.

Clinical signs of colitis are those caused by an inflammed bowel: diarrhea, fever, depression, colic, and if severe shock and death. Very early in the disease the horse may be depressed or suffering from colic without diarrhea. Colitis cases will often have a heart rate that will be a little higher, mid 50's to lower 60's, than the pain alone would account for. You should take the temperature of every horse with colic: with colitis the horse often will have a low to moderate grade fever, not a typical sign of a medical colic. The gums will usually not be normal but may range from very pale to a muddy grey. A cow patty diarrhea will be present which later will develop into a watery stool. I have seen some peracute colitis cases that were down before diarrhea developed.

The severity of the disease can be gauged using the following factors with the more to the left you go the more severe the disease:
EVALUATION Exam Findings	MILD DISEASE	MODERATE DISEASE	SEVERE DISEASE	GRAVE
Gum color:	normal light pink	slightly pale or slightly red	very pale or very reddened	purple to grey
Cappilary refill time (gums):	under 1 second	1-2 sec	2-3 sec	over 3 sec
Heart Rate:	40	40 to 50	50 to 60	over 60
Attitude:	normal	a little quiet	depressed but still responsive	nonresponsive or unable to rise
Skin Pinch (tenting):	immediatley returns to normal	remains tented for a second	remains tented for 2 or 3 seconds	does not return to normal
Diarrhea:	soft cow patty	liquid infrequent	liquid, large volume and frequent	explosive, almost continuous large volume or bloody

It is important to understand that just because a horse is displaying mild signs does not mean this is a mild disease: you could be looking at the early stages of a life threatening condition. It does mean you have more time to prevent dehydration, sepsis, shock, founder, or even death. Any signs of inflammatory bowel disease is an emergency and the veterinarian called.