Category:Colic Diagnosis in the Horse

Colic Diagnosis - Clinicopathologic Evaluation

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Abdominocentesis

The extraction and analysis of fluid from the peritoneum can be useful in assessing the state of the intestines. Abdominocentesis can be a useful diagnostic tool in determining whether the colic patient should go to surgery. It should be performed in every case of recurrent, moderate to severe or persistent colic. It should not be performed in the field due to the risks to the veterinarian and horse if the physical examination findings are suggestive of the need for surgery and referral. For normal peritoneal fluid analysis in the horse click here.

In the early stages of simple obstruction of the small and large intestine, the peritoneal fluid will look normal. A cloudy fluid is suggestive of an increased number of white blood cells, which indicates the disease is relatively advanced. The protein level of abdominal fluid can be analysed, and may also give information as to the integrity of intestinal blood vessels. Elevated lactate levels in the sample can also give an indication of the degree of compromise to bowel, particularly as a peritoneal:peripheral lactate ratio. A sanguinous fluid can be caused by an infarction, which indicates surgery is necessary. The peritoneal fluid of a case of infarction will also have an increased total protein concentration and nucleated cell count. However, sanguinous fluid can also be caused by external trauma (e.g. rib fractures), middle uterine artery rupture in post-foaling mares, intra-abdominal hemorrhage, intestinal necrosis, splenic puncture or by inadvertent bleeding caused by the veterinarian. If the spleen has accidentally be punctured then the fluid will have a greater PCV than the blood and will contain lots of small lymphocytes. Intra-abdominal hemorrhage will have a fluid with a PCV lower than the blood, few if any platelets and evidence of erythrocytophagia. Peritoneal fluid that contains food material can indicate rupture of the gastro-intestinal tract, although care should be taken that intestine has not been punctured inadvertently. The peritoneal fluid of a case with bowel rupture will be dark, turbid and smell of ingesta. It will have an increased total protein concentration due to intestinal necrosis and an increased nucleated cell count with intracellular bacteria and plant material evident grossly and microscopically.

A normal peritoneal fluid sample does not rule out a strangulating lesion. For example, in the case of a diaphragmatic hernia, the strangulating gut is contained within the thoracic cavity, so will not affect fluid within the abdominal cavity. A similar situation is true of intussuception, where the strangulating gut is contained with another piece of non-strangulating gut.

Faecal Examination

The amount of faeces produced, and its character can be helpful. The texture of the faeces can indicate digestive or dental disorders affecting prehension, mastication and absorption of the diet, as well as hydration. Parasitic disease can be diagnosed by the detection of parasite ova using fecal floatation techniques. The faeces can also be examined for the presence of bacteria, parasites, viruses and blood. Rotaviruses are a common cause of diarrhoea in foals and can be diagnosed by detection of the virus in ELISAs or by electron microscopy. Bacteria such as Escherichia coli, Campylobacter , Salmonella and Clostridium species. In areas where sand colic is known to be common, or if the history suggests it may be a possibility, faeces can be examined for the presence of sand, often by immersion in water, or simply by its texture. Diarrhea is usually indicative of a non-surgical condition, although it can be associated with life threatening conditions such as salmonellosis.

Abdominal Ultrasound

Ultrasonographic evaluation of the abdomen is extremely useful in characterizing certain components of the disease process in the foal or horse with colic. The findings of the abdominal ultrasound can distinguish surgical and medical colic patients. It is a very useful non-invasive diagnostic tool and can be used to guide other techniques such as abdominocentesis. It can be carried out trans-abdominally or trans-rectally. The latter scenario is useful for confirming andormalities palpated on prior rectal examinations.

It is important that the veterinarian is confident with the normal abdominal ultrasound of the horse in order to detect significant abnormalities. The amount and character of free abdominal fluid can be determined, as well as the determination of a specific place for safe, high-yield abdominocentesis. The appearance of intestine including distension of the lumen, increased wall thickness and motility (or lack thereof, often seen as sedimentatioon of digesta)indicate a degree of intestinal comprimise and can be extremely important in the decision for surgical or medical therapy. The large colon and cecum can be evaluated for wall thickness (particularly useful in cases of right dorsal colitis), fluidy contents (colitis/diarrhea), and sometimes displacement. The presence of mesenteric vessels associated with the large colon is generally associated with displacement. The normal anti-mesenteric vessels of the cecum can be used to trace its course. Ventral displacement of the spleen with obscuring of the left kidney is associated with nephro-splenic displacement. Visualization of sacculated large bowel immediately ventral to the liver or spleen, or non-sacculated large bowel in the ventral abdomen suggests displacement. The stomach can be evaluated for fluid distension and abnormalities of the wall. Significant fluid distention of the stomach should indicate that nasogastic decompression is needed. Abdominal ultrasound is useful in detecting diaphragmatic or inguinal herniation. Masses of the spleen, kidneys and liver can be demonstrated and may be incidental findings or causes of false colic.

Liver Biopsy and Liver Function Tests

Small Intestinal Absorption Tests

References