Ileal Impaction - Horse

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Also known as: Colic — Impaction — Simple Obstruction — Small Intestinal Simple Obstruction — Small Intestinal Obstruction — Small Intestinal Impaction

Introduction

The most common condition causing simple obstruction of the small intestinal lumen.[1]

Signalment

Adult horses

Prevalence

Ileal impaction occurs most frequently in the southeastern USA, Germany and The Netherlands.[1] 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.[2]

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.[3] It is proposed that when this forage has a high fibre content, there is an increased proportion of thin fibres which are prematurely swallowed.[4] Sudden feed changes may also contribute.[5] 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.[6] 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.[7]Impaction may also develop secondary to spastic contractions of the ileal musculature against ingesta.[1]

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.[1] The most likely differential diagnosis is proximal jejunitis, which can be challenging to rule out.

Treatment

Medical treatment may be feasible if the pain is manageable, if repeated abdominocentesis demonstrates no evidence of intestinal degeneration, if there is no nasogastric reflux and if multiple tightly distended loops of small intestine are not present on rectal examination. In this situation, balanced electrolyte solutions (administered IV) and analgesia may suffice. Substances via nasogastric tube are contraindicated, even if reflux is absent, because the small intestinal distension and reduced motility proximally will prevent these reaching the impaction. The response to medical intervention will be evidenced by a reduction in colic signs and an improvement in cardiovascular status.[8] Although medical treatment may resolve the impaction early on, surgery is typically required.

Surgical treatment comprises celiotomy followed by reduction of the impaction via extraluminal massage aided by admixing of the intestinal fluid oral to the impaction or injection of fluids intraluminally. The ingesta can then be moved into the caecum. Infusions into the impaction may include saline, carboxymethylcellulose or dioctyl sodium sulfosuccinate (DSS). An enterotomy in the distal jejunum may be instigated to evacuate impacted contents and minimise intestinal manipulation. Recurrent ileal impaction may demand a jejunocecostomy.[2]

Complications

Small intestinal distension and manipulation of the ileum at surgery may lead to post-operative ileus[9] but the risk is reduced if the duration between disease onset and surgical intervention is decreased.[2] 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.[1] Most of the problems related to adhesions are thought to occur within 2 months.[10]

Prognosis

The prognosis for survival is generally good.[2][8] The shorter the duration of colic before surgical intervention, the better the prognosis.[11] The requirement for enterotomy, enterectomy, jejunocecostomy during surgery[12] and the development of postoperative adhesions have all been associated with a poorer prognosis for survival.[10]

Prevention

  • Adequate and appropriate feeding of good quality forage
  • Avoidance of sudden dietary changes
  • An adequate tapeworm control programme
  • Avoid practices that encourage the development of anthelmintic resistance

Feacal worm egg counts do not reliably detect horses infected with A.perfoliata. An ELISA to test for the host antibody response to tapeworms has been developed with a reported sensitivity of 70% and a specificity of 95%.[13] Although this test is useful for detecting horses with a high intensity of infection, it measures past and current infection so must be interpreted in light of the anthelmintic history. More recently, a coproantigen capture ELISA has demonstrated some promise in a small sample of horses.[7] Such tests may be used as part of a targeted strategic dosing programme for anthelmintic administration.


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References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition), Merial.
  2. ↑ 2.0 2.1 2.2 2.3 Hanson, R.R, Wright, J.C, Schumacher, J, Baird, A.N, Humburg, J, Pugh, D.G (1998) Surgical reduction of ileal impactions in the horse: 28 cases. Vet Surg, 27(6):555-60. Cite error: Invalid <ref> tag; name "Hanson" defined multiple times with different content Cite error: Invalid <ref> tag; name "Hanson" defined multiple times with different content Cite error: Invalid <ref> tag; name "Hanson" defined multiple times with different content
  3. ↑ Little, D, Blikslager, A.T (2002) Factors associated with development of ileal impaction in horses with surgical colic:78 cases (1986-2000). Equine Vet J 34(5):464-8.
  4. ↑ Blikslager, A.T (2010) Obstructive Disorders of the Gastrointestinal Tract in Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) Equine Internal Medicine (Third Edition), Chapter 15, Saunders.
  5. ↑ Parks, A.H.A, Allen, D (1998) The purported role of coastal Bermuda hay in the etiology of ileal impactions: results of a questionnaire (abstract), 6th Equine Colic Research Symposium, University of Georgia, p37. In: Blikslager, A.T (2010) Obstructive Disrodersof the Gastrointestinal Tract in Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) Equine Internal Medicine (Third Edition), Chapter 15, Saunders.
  6. ↑ Proudman, C.J, French, N.P, Trees, A.J (1998) Tapeworm infection is a significant risk factor for spasmodic colic and ileal impaction colic in the horse. Equine Vet J, 30:194-199.
  7. ↑ 7.0 7.1 Kania, S.A, Reinemeyer, C.R (2005) Anoplocephala perfoliata coproantigen detection: a preliminary study. Vet Parasitol, 127(2):115-9. Cite error: Invalid <ref> tag; name "Kania" defined multiple times with different content
  8. ↑ 8.0 8.1 Hanson, R.R, Schumacher, J, Humburg, J, Dunkerley, S.C (1996) Medical treatment of horses with ileal impactions: 10 cases (1990-1994). J Am Vet Med Assoc, 208(6):898-900. Cite error: Invalid <ref> tag; name "Hanson 2" defined multiple times with different content
  9. ↑ Blikslager, A.T, Bowman, K.F, Levine, J.F, et al. (1994) Evaluation of factors associated with postoperative ileus in horses: 31 cases (1990-1992). J Am Vet Med Assoc, 205:1748-1752.
  10. ↑ 10.0 10.1 Baxter, G.M, Broome, T.E, Moore, J.N (1989) Abdominal adhesions after small intestinal surgery in the horse. Vet Surg, 18(6):409-14.
  11. ↑ Embertson, R.M, Colahan, P.T, Brown, M.P, Peyton, L.C, Schneider, R.K, Granstedt, M.E (1985) Ileal impaction in the horse. J Am Vet Med Assoc, 186(6):570-2.
  12. ↑ Parks, A.H, Doran, A.E, White, N.A, Allen, D, Baxter, G.M (1989) Ileal impaction in the horse: 75 cases. Cornell Vet, 79(1):83-91.
  13. ↑ Proudman, C.J, Trees, A.J (1996) Use of excretory/secretory antigens for the serodiagnosis of Anoplocephala perfoliata cestodosis. Vet Parasitol, 61:239-247.


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