Page 849 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

824 CHAPTER 4

VetBooks.ir Aetiology/pathophysiology obstruction has developed. Abdominocentesis usually
yields normal fluid. Haematology is unremarkable.
Muscular hypertrophy may be primary or second-
ary. If secondary, it is usually associated with stenosis
of the ileum or the ileocaecal valve. Causes of the ste- Management
nosis include ileocaecal intussusception, strongyle lar- Mild cases, where surgery is not an option, may
vae migration or mucosal or mural lesions. Muscular be treated conservatively with a laxative diet. The
hypertrophy occurs as a compensatory mechanism in potential association with intestinal parasites means
these cases. If primary, idiopathic hypertrophy of the that the deworming programme should be evaluated,
ileum may also occur. The aetiology of this condition is with particular attention paid to tapeworms. The
believed to be an imbalance in the autonomic nervous severity and frequency of clinical signs are used to
system and dysfunction at the ileocaecal valve. There determine whether surgery is required. Longitudinal
may be an increased risk with a heavy tapeworm burden. myotomies of the serosal and muscular layers at regu-
Both the circular and the longitudinal muscular lar intervals may be useful. If the lesion is localised,
layers of the ileum are affected. The abnormalities a single myotomy with transverse closure can be
can extend to the distal jejunum. In some cases, sev- performed. However, the success rate with myotomy
eral segments of the small intestine may be affected. is only fair and an incomplete or complete ileocae-
The hypertrophied muscle narrows the lumen, caus- cal or jejunocaecal bypass, depending on where the
ing a partial obstruction. This obstruction can result lesion ends, is recommended. An incomplete bypass
in local impaction and distension of the small intes- may result in impaction of the remaining loop, thus
tine orad to the lesion. obstructing the newly created opening. Furthermore,
passage of food in the remaining loop can still cause
Clinical presentation local pain. A complete jejunocaecal anastomosis with
The clinical signs will depend of the degree of formation of an ileal stump alleviates this problem.
obstruction. Intermittent colic (especially after
eating), anorexia and chronic weight loss of 1–6 Prognosis
months’ duration are common. Partial obstruction If the lesion is localised and does not involve the
may result in mild to moderate intermittent signs of remainder of the small intestine, the prognosis is fair
colic, but if the obstruction is total, the horse will be to good. If anastomosis (with or without resection) is
presented with more severe signs. NG reflux may be performed, local dehiscence of the anastomosis site,
present depending on the severity and duration of stricture and adhesions can occur.
the luminal obstruction.
ILEAL IMPACTION
Differential diagnosis
A variety of other obstructive or strangulating Definition/overview
lesions of the small intestine should be considered. Obstruction of the ileum from accumulation of
Intestinal lymphosarcoma may also result in thick- ingesta in the ileum orad to the ileocaecal opening is
ened small intestine. termed an ileal impaction. It most commonly occurs
as a primary condition, but it can also be secondary
Diagnosis to ileal pathology.
Distended loops of small intestine may be palpable p/r.
Loops of small intestine with a thickened wall may be Aetiology/pathophysiology
palpable in the upper right abdominal quadrant. These The condition is seen more often in Europe and
findings may also be observed via ultrasound exami- the southeastern USA. The condition in the USA is
nation, which can provide an objective assessment possibly related to feeding coastal Bermuda hay. In
of wall thickness. In severe cases the intestinal wall Europe the condition is thought to be secondary to
can be up to 25 mm thick. If the lesion is obstructive, local infestation with tapeworms or mesenteric vas-
small-intestinal distension orad to the lesion may also cular thrombotic disease. In the USA the disease is
be visualised. NG reflux may be present if a complete more commonly seen between June and November.