Page 876 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Gastrointestinal system: 4.2 The lower gastrointestinal tr act 851

VetBooks.ir or fenbendazole (10 mg/kg p/o q24 h for 5 days, or occur when the pelvic flexure travels in a caudal-to-
cranial direction. Once the colon is displaced, the
60 mg/kg single dose). Resistance to pyrantel has
been reported. Pasture management, including pro-
resulting in abdominal distension and pain. The vas-
vision of adequate stocking density, routine (twice normal flow of ingesta and/or gas may be restricted,
weekly) removal of faeces and pasture rotation, is cular supply to the colon is minimally affected.
important.
If intestinal infarction is present, prompt surgical Clinical presentation
intervention is required. The affected area of intes- Clinically, signs of mild to severe abdominal pain
tine must be resected. Often, resection of the entire may be evident, depending on the degree of abdomi-
affected intestine is not possible, and euthanasia is nal distension. Presentation may be acute or chronic.
required. Moderate to severe abdominal tympany may be
present. Pain can be continuous or intermittent.
Prognosis Heart rate will be elevated according to the degree
The prognosis is excellent unless intestinal infarc- of pain. Signs of toxaemia or cardiovascular com-
tion is present, in which case the prognosis is guarded promise should not be evident. Occasionally, horses
with surgical intervention and hopeless if surgery is with a nephrosplenic entrapment may appear to be
not an option. in pain, yet the heart rate may not be correspond-
ingly elevated, presumably because of vagal effects.
DISPLACEMENT OF THE LARGE COLON
Differential diagnosis
Definition/overview Any condition causing colic, particularly with
Movement of the large colon is only restricted by gaseous distension of the large colon, should be
its attachment to the caecum and transverse colon, considered.
and it is therefore relatively mobile. A variety of dis-
placements of the large colon can occur and result in Diagnosis
abdominal distension and pain. Displacement may be difficult to diagnose at times
and may be difficult to differentiate from large-colon
Aetiology/pathophysiology impaction or volvulus. Displacement should be sus-
The aetiology is unknown and likely variable. pected when there is progressive gaseous distension
Reported risk factors for displacement include with a large-colon impaction.
advancing age (>7 years), Warmblood breed, large Palpation p/r is useful for a presumptive diagno-
size, foaling and diet changes. Presumably, anything sis of right dorsal displacement. Typically, distended
that results in excessive production or accumulation colon is palpable on the right side of the abdomen
of gas within the large colon could predispose to and the caecum is not palpable. The colon may be
development of a displacement. Two common dis- palpable between the caecum and body wall. A large-
placements are nephrosplenic entrapment (left dor- colon impaction may be palpable concurrently.
sal displacement) and right dorsal displacement. Diagnosis of a nephrosplenic entrapment can be
It is presumed that gaseous distension is the incit- difficult at times. The nephrosplenic space can be
ing cause for most displacements. Often, a mild to difficult to palpate in large horses. Sometimes, a
moderate, large-colon impaction is present and is nephrosplenic entrapment can be suspected based on
presumably associated with the development of medial displacement of the spleen. It is not unusual
gaseous distension. Right dorsal displacements can to detect loops of small colon in the nephrosplenic
occur in two directions: clockwise and counter- space. These are typically incidental and must be
clockwise. Clockwise displacements are more com- differentiated from tightly entrapped large colon.
mon and occur when the pelvic flexure is displaced Transabdominal ultrasonographic examination
between the caecum and body wall in a cranial-to- can be useful to rule out a nephrosplenic entrap-
caudal direction. Counterclockwise displacements ment. If the left kidney and spleen can be visualised