Changes

=====Cardiovascular Parameters=====

=====Cardiovascular Parameters=====

Heart rate rises with progression of colic, in part due to pain, but mainly due to decreased circulating volume, decreased [[preload]], and [[endotoxemia]].  The rate should be measured over time, and its response to analgesic therapy ascertained.  A pulse that continues to rise in the face of adequate analgesia is considered a surgical indication.

Tachypnoea and tachychardia can be seen in the horse with colic. This is due to pain, but mainly due to decreased circulating volume, decreased preload, and endotoxemia.  The rate should be measured over time, and its response to analgesic therapy ascertained.  A pulse that continues to rise in rate to 60 to 70 beats per minute and weaken in quality over 6 to 8 hours in the face of adequate analgesia is considered a surgical indication. Infarctive disease is characterised by an increaseing, non-fluctuating heart rate.  

[[Mucous membrane]] colour can be assessed to appreciate the severity of haemodynamic compromise.  Reddening of membranes reflects worse prognosis, and [[cyanotic]] membranes indicate a very poor chance of a positive outcome.

Laboratory tests can be performed to assess the cardiovascular status of the patient. [[Packed Cell Volume]] (PCV) is a measure of hydration status, with a value 45% being considered significant.  Increasing values over repeated examination are also considered significant.  The total protein (TP) of blood may also be measured, as an aid in estimating the amount of protein loss into the intestine.  Its value must be interpreted along with the PCV, to take into account the hydration status.  Blood lactate levels are useful in determining severity of disease, and as a prognostic indicator; levels between 1-2mmol/L are considered normal, while levels above 5.7mmol/L are considered significant.  "Colic scores" that combine several parameters can be relatively accurate prognostic indicators, although most laboratory tests have limited use in terms of specific diagnosis.

Mucous membrane colour and moisture and capillary refil time (CRT) can be assessed to appreciate the severity of haemodynamic compromise.A reduced skin tent indicates dehydration. The mucous membranes change from pink and moist to red and dry as the circulating blood volume decreases. Reddening of the mucous membranes indicates haemoconcentration and worsens as the patient goes into shock. Reddening reflects worse prognosis, and cyanotic membranes indicate a very poor chance of a positive outcome as it it indicates that the horse is in endotoxic shock. A reduced skin tent indicates dehydration.

 

Auscultation of the abdomen, usually performed in a four quadrant approach, can be a useful tool.  Auscultation of the ventral abdomen can also be useful in regions where sand impaction is common.  Increased gut sounds are not usually found with major changes, and may be indicative of spasmodic colic, or impending diarrhea.  A decreased amount of sound, or no sound, may be suggestive of serious changes.  Trapped gas, particularly in the caecum, can often be heard by "pinging", where a flick of the finger against the skin over the affected area causes a sharp sound audible through the stethoscope.  This sound is sometimes compared to the ringing sound made by a rubber ball hitting a solid surface.

===Rectal Examination===

===Rectal Examination===

===Naso-gastric Intubation===

===Naso-gastric Intubation===

Passing a Naso-Gastric Tube (NGT) is useful both diagnostically and therapeutically.  Fluid is refluxed from the stomach, and any more than 2 litres of fluid is considered to be significant.  Increased fluid is generally a result of backing up of fluid through the intestinal tract, due to a downstream obstruction.  This finding is important as it represents a relatively advanced stage of colic, and is often a surgical indication.  Therapeutically, gastric decompression is important, since horses are unable to vomit. If fluid build up occurs, gastric rupture may occur, which is inevitably fatal.

Passing a Naso-Gastric Tube (NGT) is useful both diagnostically and therapeutically.  Fluid is refluxed from the stomach, and any more than 2 litres of fluid is considered to be significant.  Increased fluid is generally a result of backing up of fluid through the intestinal tract, due to a downstream obstruction.  This finding is important as it represents a relatively advanced stage of colic, and is often a surgical indication.  Therapeutically, gastric decompression is important, since horses are unable to vomit. If fluid build up occurs, gastric rupture may occur, which is inevitably fatal.

===Abdominocentesis===

===Abdominocentesis===

The extraction of fluid from the peritoneum can be useful in assessing the state of the intestines.  A [[sanguinous]] fluid can be caused by an [[infarction]], which indicates surgery is necessary.  However, sanguinous fluid can also be caused by external trauma (e.g. rib fractures), middle uterine artery rupture in post-foaling mares, or by inadvertent bleeding caused by the procedure itself.  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.  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 extraction of fluid from the peritoneum can be useful in assessing the state of the intestines.  A [[sanguinous]] fluid can be caused by an [[infarction]], which indicates surgery is necessary.  However, sanguinous fluid can also be caused by external trauma (e.g. rib fractures), middle uterine artery rupture in post-foaling mares, or by inadvertent bleeding caused by the procedure itself.  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.  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.

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.

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===

===Faecal Examination===

===Abdominal Ultrasound===

===Abdominal Ultrasound===

Ultrasonographic evaluation of the abdomen is extremely useful in characterizing certain components of the disease process. 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 small intestine, including distension, wall thickness and motility (or lack thereof, often seen as sedimentatioon of digesta) 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 distension and abnormalities of the wall.  Abdominal ultrasound is useful in detecting diaphragmatic or inguinal herniation.  Abnormalities of the liver or kidneys, both potential causes of false colic, are often detectable with ultrasound.

Ultrasonographic evaluation of the abdomen is extremely useful in characterizing certain components of the disease process. 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 small intestine, including distension, wall thickness and motility (or lack thereof, often seen as sedimentatioon of digesta) 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 distension and abnormalities of the wall.  Abdominal ultrasound is useful in detecting diaphragmatic or inguinal herniation.  Abnormalities of the liver or kidneys, both potential causes of false colic, are often detectable with ultrasound.