ISSN 2398-2977      

Colon: small - obstruction



  • Obstruction of the small colon may be due to intraluminal blockage such as impaction, or may be associated with strangulation.
  • Signs: include symptoms of abdominal pain.
  • Diagnosis: rectal examination, however exploratory laparotomy may be required.
  • Treatment: in cases of simple obstruction medical treatment is usually successful, however some cases require surgery.
  • Prognosis: is good in those cases which do not require surgery.



  • Causes of small colon impaction include:
    • Poor teeth and thus poor mastication of food.
    • Inadequate or inappropriate food, or a change in food and regime.
    • Hunger due to inadequate food or worms.
    • Eating of bedding, or other inappropriate material that is poorly digested (may occur after the institution of box rest in horses that are normally use to exercise and more food).
    • Lack of sufficient water.
  • The small colon is a predeliction site for impactions, due to it's narrowness, and anything that compounds this by further compressing the luminal size can predispose to the devlopment of small colon obstruction. Such factors include:
    • Extraluminal abnormalities such as lipomata, strictures and fibrous bands, adhesions and mesenteric abcesses can cause luminal compression, as can torsion, intussusception or strangulation of the bowel.
    • Intramural disorders such as inflammatory or neoplastic disease. Lymphosarcoma is the commonest form of neoplasia in this area. Inflammation due to submucosal edema, or rectal discomfort (such as following repair of a recto-vaginal tear) can also be involved, as can intramural hematomas.
    • Intraluminal masses such as foreign bodies/fecoliths/phytobezoars can also be involved.
  • Motility disorders may also be involved. Interestingly, one survey showed 25% of those horses that went to surgery for correction of a small colon impaction wereSalmonellapositive. Correlation of with presence ofSalmonellamay be associated with that organism's effects on gut motility.
  • Also see:

Predisposing factors

  • Poor dental care.
  • Poor quality food/eating of bedding.
  • Worm burden.
  • Altered motility from enteric infection.
  • Water deprivation.



  • The two most common causes of small colon obstruction are fecoliths   Gastrointestinal: fecalith / bezoar  and enteroliths   Gastrointestinal: enterolith  .
  • There may or may not be associated narrowing of the bowel lumen that predisposes to this.
  • In most cases there is gradual development of an impaction. Mild abdominal pain is caused by stretching of bowel wall and mesenteric traction. In cases where there is predisposing bowel disease, or where bowel compromise develops due to the presence of the impaction, pain due to ischemia, infarction and toxemia also occurs.
  • In uncomplicated cases, fluid absorption from the gut can continue and progression of disease is slow. Symptoms such as dehydration may take days to develop.
  • In more severe cases, where intestinal compromise is involved, circulatory abnormalities and more severe pain are seen.
  • Obstruction of the small colon occurs either due to impaction with ingesta or strangulation or compression.
  • Food matter accumulates in colon.
  • The impacted ingesta becomes progressively harder and drier with time, and thus more and more solid.
  • Peristaltic waves become weaker due to the presence of a blockage.
  • Dehydration may occur due to decreased eating and drinking, although this generally comes late in the course of disease since fluid absorption continues to occur proximal to the lesion.
  • In cases of simple obstruction, vascular compromise occurs late in the course of the disease (if at all) due to damage to the gut wall due to pressure and stretching.
  • Stasis of intestinal fluid proximal to the obstruction results in the multiplication of intestinal bacteria and the release of gas. Increased pressure within the bowel due to fluid and gas build up causes distension, which results in an increase in pain, as well as a decrease in peristalsis. The result is progressive filling and swelling of the gut, and atonia of the gut wall.
  • Without treatment, progressive damage to the intestinal wall occurs, with degeneration, cell sloughing, and vascular compromise. Endotoxemia   Endotoxemia: overview  may result, and this can cause further sensitization of the pain receptors. Electrolyte and fluid sequestration contribute to the development of circulatory collapse. Metabolic acidosis is not uncommon.
  • In those cases where there is damage to the bowel wall in the earlier stages of the disease, these circulatory changes occur earlier.


  • In cases of simple obstruction, symptoms may take several days to develop, and treatment may need to be continued for several days.

These cases are more difficult to treat than large colon impactions and take more time for resolution.

  • In cases where ishemia, infarction, or strangulation of the bowel is present, symptoms of circulatory compromise develop simultaneously with signs of severe abdominal pain.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Pilati N, Masciarelli A E, Werner L A & Spreayberry K A (2013) Small colon obstruction by an ovarian pedicle as an acquired condition in a foal. Equine Vet Educ 25 (4), 290-292 VetMedResource.
  • Prange T (2013) Small colon obstruction in foals. Equine Vet Educ 25 (6), 293-296 VetMedResource.
  • Southwood L L (2006) Potential causes and alternate methods for diagnosis and treatment of small colon submucosal hematoma: can we extrapolate from human medicine? Equine Vet Educ 18 (2), 71-74 Wiley Online Library.
  • Stahel S, Riley C B, Wichtel M & Daoust P Y (2006) Nonstrangulating small colon obstruction caused by a submucosal hematoma. Equine Vet Educ 18 (2), 67-67 VetMedResource.
  • Smith L J & Mair T S (2004) Recurrent small colon obstructions in a foal age 7 weeks affected by a mandibular fracture. Equine Vet Educ 16 (6), 284-288 VetMedResource.
  • Dart A J et al (1992) Abnormal conditions of equine descending colon. JAVMA 200, 971-978 PubMed.
  • Ruggles A J et al (1991) Medical and surgical management of small colon impaction on horses (1984-1989). JAVMA 199, 1762-1766 PubMed.

Other sources of information

  • Rose R J & Hodgson D R (1993) Manual of Equine Practice. Saunders. ISBN: 0 7216 3739 6.

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