Page 881 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

856 CHAPTER 4

VetBooks.ir INTRAMURAL LESIONS OF lesion of the colonic wall result regardless of whether
THE LARGE COLON
the aetiology of the lesions is neoplastic, bacterial or
Definition/overview inflammatory, with potential partial or complete
obstruction of the colonic lumen.
Intramural lesions (lesions within the wall) of the
large colon include lymphosarcoma, adenocarci- Clinical presentation
noma, segmental eosiniphilic colitis and intestinal The clinical signs are non-specific. The most com-
wall abscess (Fig. 4.172). They are uncommon and mon clinical signs are mild to moderate recurrent
usually lead to mild to moderate intermittent colic. colic episodes associated with abdominal distension
Treatment is surgical and the prognosis varies with and pelvic flexure impaction. Lethargy, weight loss,
the aetiology of the lesions. pyrexia and diarrhoea may be observed in horses
with intramural lesions of the large colon.
Aetiology/pathophysiology
Multicentric and intestinal lymphosarcoma and Differential diagnosis
adenocarcinoma have been reported as the cause Causes of simple colon obstruction (food and foreign
of intramural lesions of the large colon in a limited body impaction) and primary large-colon tympany
number of horses. Segmental eosinophilic colitis is are the major differential diagnoses for intramural
an uncommon disease that results in a local thick- lesions of the large colon.
ening and obstructive lesion of the colon in horses.
The precise aetiology is not known, but parasite Diagnosis
involvement is suspected. In rare cases abdominal An abdominal mass attached to the large colon and/or
abscessation limited to the wall of the large colon large-colon distension may be palpable p/r in horses with
can be the cause. Local thickening and obstructive intramural lesions of the large colon. Ultrasonographic
examination of the large colon may show an increased
wall thickness or confirm the presence of an abdomi-
4.172 nal mass. Peritoneal fluid total nucleated cell count and
protein concentration are usually increased, but exfoli-
ated tumour cells are only rarely observed. A definitive
diagnosis is usually made on exploratory laparotomy,
during which biopsies are taken.

Management
Horses with intramural colonic lesions are usu-
ally initially treated in a supportive manner using
a restricted diet, analgesics, intravenous and/or
enteral fluids and laxatives. Clinical signs are often
temporarily responsive to this medical treatment,
but they recur as food is reintroduced or the action
of the analgesics abates.
Affected horses are eventually managed using an
exploratory laparotomy. Identification of the lesion
and differentiation between intestinal neoplasia and
an abscess may be possible grossly or after histopathol-
Fig. 4.172 A large intramural abscess found in ogy of biopsy material. If discrete areas of neoplasia
the large colon of a horse presented for exploratory or eosinophilic colitis are identified, the affected areas
laparotomy for investigation of chronic abdominal can be resected. Intestinal abscesses are treated using
pain. (Photo courtesy Graham Munroe) drainage with or without marsupialisation, intestinal