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(Merck)

Signalment

Adult horses

Prevalence

Most common in the southeastern USA, Germany, and The Netherlands.(Merck) Anoplocephala perfoliata has a prevalence as high as 60% in some geographical areas and has been associated with increased risk for serious conditions in the horse including bowel irritation, ileal impaction, and spasmodic colic. (Kania)

Aetiology

In the southeastern United States, feeding of sub-optimal Coastal Bermuda hay and lack of administration of the anthelmintic pyrantel pamoate have been implicated as a risk factors. It is thought this forage contains a high amount of thin fibres which are prematurely swallowed. Sudden feed changes may also be a risk (38). In the UK, infection with the tapeworm Anoplocephala perfoliata is an important risk factor. Data suggests that more than 80% of ileal impactions were associated with serological or faecal evidence of tapeworm infection(39). Impaction may also develop secondary to spastic contractions of the ileal musculature against ingesta.(Merck)

Clinical Signs

Typical signs associated with small intestinal obstruction:

• Moderate to severe colic
• Reduced boriborygmi
• Tachycardia
• Nasogastric reflux may take a considerable time to develop because the ileum is the distal-most part of the small intestine. Reflux is found in 50% of horses requiring surgical conrrection for ileal impaction(35,41)

Diagnosis

Usually made at surgery. Although early rectal examination may permit identification of the impaction low in the right caudal abdominal quadrant, subsequent distention of the jejunum may make this identification difficult or impossible. The most common differential diagnosis is proximal jejunitis, and distinguishing the 2 conditions can often be difficult. Because the horse’s condition initially may remain stable and the degree of abdominal pain may be mild, many horses with this condition are not referred for intensive care or surgery for >18 hr. The protein concentration of the peritoneal fluid may increase if the impaction has persisted for this long. Rectal palpation may identify loops of distended small intestine as the condition progresses.

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.

Complications

Extensive small intestinal distension and intraoperative manipulation of the ileum may lead to postoperative ileus(42) but the risk is reduced if the duration between disease onset and surgical intervention is decreased.(35)Depending on the degree of damage to the serosal surface of the small intestine at the time of surgery, complications may develop several weeks after surgery due to intra-abdominal adhesions.(Merck)

Prognosis

The prognosis for survival is good(35,36).

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)