Ileal Impaction - Horse

Also known as:

Colic Impaction Simple Obstruction Small Intestinal Simple Obstruction Small Intestinal Obstruction Small Intestinal Impaction

Description

The most common condition causing simple obstruction of the small intestinal lumen.

Signalment

Adult horses

Prevalence

Ileal impaction occurs most frequently in the southeastern USA, Germany and The Netherlands. In the southeastern USA, there appears to be an increased prevalence in the autumn which may relate to changing weather and feedng regimes at that time of year.

Aetiology

In the southeastern United States, feeding of poor quality coastal Bermuda hay and lack of administration of the anthelmintic pyrantel pamoate have been implicated as risk factors. It is proposed that when this forage has a high fibre content, there is an increased proportion of thin fibres which are prematurely swallowed.(Bliks) Sudden feed changes may also contribute. In the UK, infection with the tapeworm Anoplocephala perfoliata is an important risk factor. Proudman and colleagues (1998) found that more than 80% of ileal impactions were associated with serological or faecal evidence of tapeworm infection. Anoplocephala perfoliata infects up to 60% of horses in some geographical areas and has also been implicated as a risk factor for bowel irritation and spasmodic colic.Impaction may also develop secondary to spastic contractions of the ileal musculature against ingesta.

Clinical Signs

Typical signs associated with small intestinal obstruction:

• Moderate to severe colic
• Reduced borborygmi
• Tachycardia
• Nasogastric reflux may take a considerable time to develop because the ileum is the distal-most part of the small intestine.

Diagnosis

Early rectal examination may reveal the impaction low in the right caudal abdominal quadrant. Subsequent distention of the jejunum will be palpable per rectum but may preclude palpation of the impaction, thus the definitive diagnosis is often made at surgery. Many horses with ileal impaction are delayed in their referral because initially their colic is mild and their condition deceptively stable. Abdominocentesis may show an elevated protein concentration if the impaction has persisted for more than about 18 hours. The most likely differential diagnosis is proximal jejunitis, which can be challenging to rule out.

Treatment

Medical treatment with fluids and liquid paraffin may resolve the impaction early on(36) but surgery is typically required. At surgery, fluids such as saline or carboxymethylcellulose can be directly infused into the mass so that the impaction can be manually broken down and massaged into the caecum. Dioctyl sodium sulfosuccinate (DSS) may be included in the infusion to help disrupt the mass. An enterotomy in the distal jejunum should be considered to evacuate impacted contents and reduce intestinal manipulation.Theileal impaction was reduced by extraluminal massage aided by admixing of intestinal fluid oral to the impaction or injection of fluids intraluminally and then movement of the ingesta into the cecum. One horse initially treated by manual reduction required jejunocecostomy twice for management of recurrent ileal impaction.Ileal impactions can be successfully reduced by celiotomy and extraluminal massage and injection techniques to soften the ingesta for passage into the cecum without enterotomy or bypass techniques in most horses. (Hanson)

Treatment consisted of intravenous administration of a balanced electrolyte solution, nasogastric intubation and siphonage, and administration of analgesics. Mineral oil was administered after gastric reflux had ceased. Mean time for resolution of ileal impaction was 11.7 hours. Medical treatment may be a viable alternative for horses that cannot have surgery,provided persistent signs of severe pain or progressive gaseous distention ofthe small intestine are not features of the condition. Improvement ofcardiovascular status, reduction in signs of abdominal pain, decrease in distentionof loops of small intestine during repeated transrectal examination, softeningof the impaction, and decreases in amounts of gastric reflux were indicative ofa response to medical treatment.(Hanson Schumacher)

Reflux is found in 50% of horses requiring surgical conrrection for ileal impaction(35,41)

Complications

Small intestinal distension and manipulation of the ileum at surgery may lead to post-operative ileus but the risk is reduced if the duration between disease onset and surgical intervention is decreased. Depending on the degree of damage to the serosal surface of the small intestine at surgery, complications may develop several weeks after surgery due to intra-abdominal adhesions. Most of the problems related to adhesions are thought to occur within 2 months.

Prognosis

The prognosis for survival is generally good.<ref name="Hanson 2">Hanson, R.R, Schumacher, J, Humburg, J, Dunkerkley, S.C (1996) Medical treatment of horses with ileal impactions: 10 cases (1990-1994). J Am Vet Med Assoc, 208(6):898-900.<ref>Enterotomy,enterectomy, and/or jejunocecostomy performed during surgery had a deleteriouseffect on survival.(Parks)Itwas concluded that the shorter the duration of colic before surgicalintervention, the better the prognosis.(Embertson)Furthermore, the earlier development of postoperativeadhesions was associated with a poorer prognosis for survival.(Baxter)

Prevention

Faecal tapeworm ELISA test: senstivity 70%, specificity 95%(40). Identification of infected animals based upon detection of eggs in feces is labor intensive and unreliable. This study involved the development of a test for A.perfoliata coproantigen using an antigen capture enzyme linked immunosorbent assay (ELISA) and correctly distinguished between infected and uninfected animals in a trial with a small sample size.(Kania)