Page 877 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

852 CHAPTER 4

VetBooks.ir in direct apposition, then an entrapment is very specific measures can be taken. Administration of
phenylephrine (3–5 µg/kg/min for 15 min), fol-
unlikely. Conversely, identification of a gas-filled vis-
cus obliterating visualisation of the dorsal border of
the spleen suggests the presence of a nephrosplenic lowed by 15–20 minutes of lunging or jogging is
sometimes effective at correcting the displace-
entrapment. An inability to visualise the left kidney ment. Phenylephrine causes splenic contraction,
is not, in itself, diagnostic. If the displaced colon is making it easier for the entrapped colon to return
not gas filled, a displacement may not be identified to its normal position. The effects of phenylephrine
ultrasonographically. are short term and administration can be repeated.
NG reflux is not typically present with displace- Rolling under general anaesthesia is another treat-
ment of the large colon. Abdominocentesis can be ment option. The affected horse should be anaes-
a useful technique when deciding whether surgical thetised, placed in right lateral recumbency, rolled
intervention is required. Peritoneal fluid analysis is into dorsal recumbency and the hindquarters
usually normal in an uncomplicated displacement. elevated. The horse should then be rocked from
side-to-side for 5 minutes, dropped into left lat-
Management eral recumbency and then sternal recumbency, at
Often, medical therapy will be successful. Feed which point palpation should be repeated. Rolling
should be withheld. Fluid therapy is useful for can be repeated numerous times. Phenylephrine
softening an impaction, if present, and to stimu- can be administered following induction of anaes-
late intestinal motility. Intravenous fluid therapy thesia as described above. Rolling can be success-
is preferred, but oral therapy (up to 8–10 litres ful in >90% of cases; however, the success rate is
q30 min) can be useful in milder cases. It is not likely to be lower in horses with marked gaseous
unusual for horses to experience more pain after distension. Surgery may be required in severely
fluid therapy has been initiated as a result of painful cases, those that do not respond to medi-
increased colonic distension. Analgesics should be cal treatment or cases in which rolling has been
provided as required. attempted but has been unsuccessful. Midline coe-
The horse should be re-examined frequently to liotomy is most commonly performed; however, a
ensure that a more severe intestinal accident such as standing left flank approach has been used suc-
a large-colon volvulus has not developed. In some cessfully. While less expensive and associated with
cases, horses will have severe, progressive abdominal a shorter recovery period, the standing approach
distension and intractable pain. Surgical interven- is limited by the fact that the surgeon is not able
tion is indicated in these cases. It is unlikely that a fully to explore the abdomen or correct any other
displacement will correct spontaneously if marked abnormality that may be present, such as a large-
tympany is present. If surgery is not an option in colon impaction.
such cases, trocharisation of the abdomen may tem-
porarily relieve intestinal tympany. Prognosis
Feed should be withheld until the displacement Overall, the prognosis is very good, with the vast
resolves. Occasionally, horses will improve clinically, majority of cases responding to medical treatment.
gaseous distension will abate, an impaction (if pres- While uncommon, some horses will develop repeated
ent) will resolve yet the colon will remain displaced displacements. As with any large-colon disease an
after a few days of medical therapy. Very conservative underlying cause should be sought and addressed
feeding might be beneficial to stimulate intestinal where possible to reduce the risk of reoccurrence.
motility and resolve the displacement. Sometimes, Techniques such as ablation of the nephrosplenic
however, surgical correction will be required. space, colopexy or large-colon resection should be
Left dorsal displacement of the colon lateral to considered in horses that develop recurrent displace-
the spleen but without entrapment in the nephro- ments requiring surgical correction. Dietary and
splenic space will often correct with conservative management changes should be attempted prior to
therapy. If nephrosplenic entrapment is present, colopexy or large-colon resection.