Page 883 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

858 CHAPTER 4

VetBooks.ir 4.173 SMALL-COLON STRANGULATION

Definition/overview
Small-colon strangulation consists of obstruction
to the vasculature of the small colon and ischaemic
damage to the intestinal tissue. This may occur due
to a strangulating lipoma, volvulus or entrapment
of the small colon through a congenital or acquired
defect. Strangulating lipomas (see p. 821) and small-
colon volvulus are covered elsewhere.

Aetiology/pathophysiology
The aetiology considered here is small-colon stran-
gulation secondary to herniation or incarceration in
Fig. 4.173 Intraoperative photograph of an impacted a congenital or acquired mesenteric or ligamentous
small colon in a miniature pony showing a large rent. The small colon has a short mesentery com-
amount of the small colon distended with firm faecal pared with the distal small intestine, which accounts
material. (Photo courtesy Graham Munroe) for the lower incidence of strangulation. However,
the small colon can become entrapped in the gas-
trosplenic ligament, broad ligament, caecocolic fold
tolerates them well. This procedure can be associ- and mesocolon and through a vaginal tear. Inguinal
ated with traumatic rupture of the small colon. and umbilical herniation of the small colon have
Surgical treatment is recommended in horses also been reported. Anatomical differences in the
with severe impactions or when the impaction fails size and shape of intra-abdominal ligaments have
to respond to medical treatment (Fig. 4.173). A coe- been identified, and there may be a predisposition
liotomy is performed, the impacted portion of the for horses to acquire defects. Congenital defects
small colon is identified, and a combination of man- including vitelloumbilical anomalies contribute to
ual massage and intraluminal irrigation is used to abnormal spaces through which the small colon can
break the impaction down and evacuate the ingesta become incarcerated.
through the anus. Intraluminal irrigation is per- Once entrapped, the vascular supply to the small
formed by inserting a long rubber hose through the colon becomes obstructed and the tissues become
anus and infusing warm water into the small-colon oedematous and turgid. Further swelling of the
lumen. entrapped intestine obstructs arterial supply to the
Anecdotally, horses with small-colon impaction intestine, resulting in ischaemic damage to the intes-
seem to have a high incidence of developing salmo- tine. Orad distension of the small colon, transverse
nellosis in some areas. The reason for this is unclear, colon and ascending colon is a consequence of intra-
but this possibility should be considered during the luminal obstruction.
management of affected horses, particularly if diar-
rhoea develops. Clinical presentation
Horses with strangulating obstruction can present
Prognosis with signs ranging from mild to moderate abdomi-
Horses that respond to medical conservative treat- nal discomfort to acute severe abdominal pain. NG
ment have a good prognosis for survival, whereas reflux is an inconsistent finding.
horses undergoing surgery commonly develop post-
operative complications such as fever, diarrhoea, Differential diagnosis
salmonellosis and laminitis. The prognosis for these Differential diagnoses for this condition include any
horses is guarded. strangulating obstruction of the intestine in horses.