Page 884 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Gastrointestinal system: 4.2 The lower gastrointestinal tr act 859

VetBooks.ir This includes strangulating lipomas, inguinal and mechanical abrasion due to the passage of faeces of
lower water content, a higher collagenase activity
other hernias, volvulus, epiploic foramen entrap-
ment and entrapment of other segments of bowel
sues. However, recent reports suggest that the prog-
in mesenteric or ligamentous rents. Small-intestinal and supposedly poorer vascularity to the healing tis-
strangulations tend to occur more acutely and with nosis may be better than previously thought.
a more rapid deterioration in clinical signs and hae- The most proximal and distal aspects of the small
matological parameters. colon may not be able to be completely exteriorised
at the time of surgery, which may hinder surgical
Diagnosis repair or increase the risk of faecal contamination.
The variable location of the strangulating obstruction Taken together, a prognosis of approximately 50%
can lead to inconclusive rectal findings, but a common for these cases is reasonable.
finding is impaction within the cranial small colon and,
in chronic cases, colonic distension. Transrectal ultra- SMALL-COLON OBSTRUCTION
sound is useful for diagnosing small-colon impac-
tions. Peritoneal fluid is often serosanguineous with Definition/overview
an elevated protein concentration and nucleated cell Small-colon obstruction can be intraluminal or
count. An elevated blood lactate level may be useful extraluminal in origin. Causes for intraluminal
for demonstrating tissue ischaemia. Ultrasonographic obstructions include impaction, foreign bodies,
findings include a distended, non-motile small colon enteroliths, faecaliths and bezoars (Fig. 4.174) (see
with a thickened wall (>3–4 mm). Normal wall thick- Small-colon impaction, p. 857). Causes for extralu-
ness of the colon and small intestine may help localise minal obstruction include intramural haematoma
the lesion to the small colon. and, rarely, neoplasms such as leiomyomas.

Management Aetiology/pathophysiology
As with all intestinal strangulations, surgical man- Foreign bodies involved in small-colon obstruc-
agement consisting of relieving the strangulation tions are usually nylon, plastic or rubber material
and assessing the viability of the lesion is critical. from halters, hay nets, bale twines, synthetic fencing
Intestine considered to be non-viable should be
resected.
Several techniques for anastomosis of the small 4.174
colon are acceptable, but a common technique is a
sutured, two-layered, end-to-end anastomosis. The
first layer consists of a non-mucosa-penetrating,
simple interrupted apposing pattern. The second
layer consists of an inverting pattern (e.g. continuous
Cushing suture pattern interrupted at 180°). Pelvic
flexure enterotomy should be considered to decrease
the load of ingesta passing by the surgical site in the
immediate postoperative period.

Prognosis
It is well recognised that strangulating intestinal
obstructions have a poorer prognosis than non- Fig. 4.174 A large trichobezoar is being removed
strangulating lesions. Furthermore, resection and from the small colon at exploratory laparotomy via a
anastomosis of the small colon is considered to have flank incision. Note the careful draping around the
a higher complication rate than more proximal sites, colon to minimise contamination of the abdomen.
due to increased bacterial loads of the ingesta, greater (Photo courtesy Graham Munroe)