Discussion

Introduction:
When presented with a horse with colic the intention should always be to achieve as accurate diagnosis as possible under the circumstances and administer appropriate treatment to maintain the welfare of the patient. Where the initial treatment is not successful the clinician usually considers referral. If referral is not an option it is vitally important that appropriate medical treatment is administered early in the course of the disease and that a tentative diagnosis is given in the light of lack of resources and/or surgical facilities not being an option. This may indicate whether the horse will respond to medical treatment or may require euthanasia if its condition does not improve or deteriorates.

Reasons why referral is not an option:
- Financial - lack of funds/uninsured
- Financial - horse passed its prime and owner doesn't think expense is justified
- Financial - owner perceives horse will not perform to same level following surgery and has no breeding potential
- Age - owner thinks horse is too old to undergo surgery
- Emotional - owner cannot cope with the emotional stress of horse undergoing surgery
- Location - remote from referral centre e.g. island

A clear discussion should take place with the owner on true and perceived risks and costs of referral. In cases where referral is not an option referral centres are usually willing to give advice on management of colic cases.

Clinical examination:
When called to examine a horse with colic it is essential to obtain a detailed history of the condition. Factors such as when the horse was last seen normal and when the patient was first noticed to be suffering from colic can provide useful information on timescale. Wherever possible, as thorough an examination should be performed on the first visit. This should include assessment of degree of pain, demeanour, degree of abdominal distension, presence and quality of borborygmi, the cardiovascular status (heart rate, mucous membranes, temperature of extremities), rectal temperature and a rectal examination. In horses with significant pain or cardiovascular impairment a naso gastric tube should be passed to check for reflux or excessive gas. Successive rectal examinations provide the clinician with information relating to changes in filling and distension of sections of the gastrointestinal tract. The early diagnosis of such conditions such as pelvic flexure impaction or nephro splenic entrapment may affect their outcome or duration and cost of treatment.
The clinician may consider performing abdominocentesis at the first examination if the colic is severe, which may provide valuable information on intestinal vascular compromise. It could also be useful to compare notes at a subsequent examination. If the colic is unresponsive to treatment administered at the first examination, abdominocentesis should be seriously considered at the second examination, unless there is evidence of distended dependant gut, which will increase the likelihood of bowel penetration. The use of diagnostic transabdominal ultrasound with 2.5-3.5 MHz probes has become standard practice for assessment of colic cases in referral centres. Many of the commercially available portable ultrasound machines with higher frequency probes used 'in the field' are capable of producing diagnostic images for imaging distended small intestine, which is often close to the ventral body wall. It may also be possible in some cases to diagnose the presence of distended loops of small intestine by transrectal ultrasound. Transabdominal ultrasound may also be of value for locating pockets of peritoneal fluid when performing abdominocentesis.
Where cases are unresponsive to the treatment administered at the first examination and no diagnosis is obtained the horse should be re-examined within 1 - 2 h depending on the severity.

Laboratory tests:
Blood samples obtained may provide useful information on hydration status, protein levels and inflammatory processes. Serum and peritoneal lactate estimations may provide a guide to cardiovascular collapse and intestinal circulation and hence aid in the assessment of prognosis. There are various portable analysers commercially available to provide reliable lactate values.

Treatment to be considered:

Analgesics:
Any analgesic administered should alleviate the signs of visceral pain without masking the symptoms of increasing more severe pain.

Nonsteroidal anti-inflammatory agents:
Flunixin (1.1 mg/kg bwt) is generally considered to be a more effective analgesic than phenylbutazone (4.4 mg/kg bwt) for visceral pain. Ketoprofen (2.2 mg/kg bwt) produces good visceral analgesia but is less potent than flunixin and more potent than phenylbutazone. Flunixine does however possess the ability to reduce the severity of pain and lessen alterations in mucous membranes and heart rate through its anti-endotoxic affects in horses with strangulating lesions. This could potentially produce a false sense of security in some colic cases. If horses still colic following the administration of flunixine there is a high chance they could be suffering from a surgical lesion. Repeated doses should only be given when the clinician has obtained a diagnosis e.g. pelvic flexure impaction. Repeated doses should not be administered where no diagnosis is achieved and cardiovascular parameters are deteriorating. In such cases euthanasia should be seriously considered where referral is not an option as there is no point in prolonging the horse's suffering unnecessarily.

Alpha2 agonists
Domosedan (30- 50 microgram/kg bwt) is considered to be a more potent
sedative and analgesic than romifidine and xylazine and the same policy as outlined above for flunixine should be adopted where referral is not an option.

Opiates
Butorphanol (0.02 - 0.1 mg/kg bwt ) is the most frequently used opiate for treating colic, which provides good visceral analgesia without masking signs of more severe pain. Pethidine is shorter acting.




Antispasmolytics:
Butylscopolamine (0.2 mg/kg bwt) is a spasmolytic and analgesic agent with particular activity on the smooth muscle of the digestive tract and is often combined with metamizole (25 mg/kg bwt), which is a nonsteroidal anti-inflammatory agent.

Catecholamines:
Phenylephrine can be infused at a dosage of 18 - 20 mg in 1 litre of normal saline over 10 - 15 min, in cases of nephrosplenic impaction, to produce splenic contraction.

Laxatives:
These are used mainly in cases of large colon impaction.
- Osmotic laxatives - draw water into the GI tract to soften ingesta e.g. magnesium sulphate (0.5 - 1.0 g/kg bwt, sodium chloride (1 - 1.5 g/kg bwt).
- Mineral oil - lubricates ingesta and safe to use for prolonged periods at a dosage of 5 - 10 ml/kg bwt. Can be combined with osmotic laxatives
- Psyllium hydrophilic muciloid (1 g/kg bwt q.i.d.) - bulk- forming laxative to move sand/soil

When laxatives do not resolve the impaction the possibility of a large bowel displacement should be considered.

Enemas:
These are primarily used in cases of colic in foals due to retained meconium and include phosphate, acetyl cysteine and soapy water.

Lungeing:
Lungeing can sometimes resolve some milder intestinal displacements and is worth considering in some cases in addition to post phenylephrine infusion for cases of nephrosplenic entrapment.

Decompression:
- Passage of a nasogastric tube to relieve gastric tympany or gastrointestinal reflux
- Caecal trocharisation to relieve caecal tympany

Fluid therapy:
With the exception of anterior enteritis replacement fluid therapy has little place in cases where referral is not an option. Cases suffering from severe pain and cardiovascular imbalance should be subjected to euthanasia and cases with mild fluid imbalance rapidly correct themselves.

Salvage procedures:
Where a mare at term is suffering from colic with deteriorating cardiovascular parameters it may be worth considering trying to save the foal.