Epiploic Foramen Entrapment - Horse

Description

Epiploic foramen entrapment in the horse refers to the displacement of a segment of small intestine through a small hole or foramen that separates the omental bursa from the peritoneal cavity. This form of obstruction accounts for between 2% and 8% of horses undergoing exploratory laparotomy for colic and is one of the most common forms of internal hernia in the horse.

Pathogenesis

The epiploic foramen is located in the right dorsal abdomen and is bordered by the vena cava, hepatic portal vein, liver and pancreas. Most incarcerations are caused by small intestine passing from the left side of the abdomen through the epiploic foramen to the right side of the abdomen. The ileum and the jejunum are the most commonly incarcerated portions of small intestine and the length of bowel affected may vary from a few centimetres up to 17m. Strangulation of the affected portion occurs as a result of entrapment in the majority of cases and approximately 80% of affected horses have irreversible vascular compromise of the herniated small intestine.

Signalment

Horses of all breeds may be affected but an increased prevalence has been reported in Thoroughbreds. Older horses are thought to be more prone to developing epiploic foramen entrapment and it has been hypothesised that this may be due enlargement of the epiploic foramen following age-related atrophy of the right liver lobe. However, the disease has also been reported in foals. Crib-biting behaviour is also thought to increase the risk of entrapment.

Clinical signs

The presentation of this condition is similar to that of other strangulating lesions such as small intestinal volvulus. Horses with epiploic foramen entrapment frequently exhibit acute onset and severe abdominal pain that is usually non-responsive to analgesia. This is often characterised by clinical signs including rolling, pawing at the ground, flank watching and kicking at the abdomen. Other clinical signs may include tachycardia, tachypnoea and reduced borborygmi. If endotoxaemia has occurred other clinical features may include a prolonged capillary refill time and congested mucous membranes. A rare feature of the condition is sudden death due to rupture of the portal vein and subsequent haemorrhage.

Diagnosis

Definitive diagnosis of epiploic foramen entrapment may not be straightforward and is usually made at surgery. Rectal palpation is often unrewarding due to the anterior position of the lesion but a marked pain response to traction of the caudal caecal band may aid in distinguishing epiploic entrapment from other conditions. Distended coils of small intestine may also be identified. Nasogastric reflux of large volumes of alkaline gastric fluid is frequently present but may not lead to pain relief. Transabdominal ultrasonography may reveal distended, hypomotile small intestine and small intestine identified in the right dorsal quadrant of the abdomen is highly suggestive of the disease. Abdominocentesis is often useful to determine the degree of strangulation and peritoneal fluid may be serosanguineous with an increased lactate, total protein and leukocyte count. If the herniation occurs from right to left however, the tranudation enters the omental bursa and may not be collected by abdominocentesis.

See also Colic Diagnosis in Horses

Treatment

Initial treatment consists of gastric decompression, fluid therapy and analgesia. If epiploic foramen entrapment is suspected, surgical intervention is required. Surgical treatment of the condition is not straightforward due to the inaccessibility of the foramen and the delicate surrounding structures. A ventral midline exploratory coeliotomy is performed and palpation of small intestine (other than the duodenum) in the right dorsal quadrant of the abdomen will confirm diagnosis. The encarcerated portion of intestine is reduced by gentle traction; decompression may be required prior to reduction if the segment is oedematous or filled with ingesta. Manual dilation of the foramen in order to aid reduction has been reported but this may lead to rupture of the portal vein and great care must be taken when doing so. The viability of the affected intestine is assessed and a resection and anastamosis may be performed if necessary.

Prognosis

The prognosis following surgical treatment is considered to be poor, especially if the length of bowel affected is long. The prognosis may be altered by the extent of strangulation observed at surgery and the presence of endotoxaemia. Recurrence of epiploic foramen entrapment several months or years later has been reported in a small number of cases.

References

• Bentz, B. (2004) Understanding Equine Colic Eclipse Press
• Bertone, J. (2006) Equine Geriatric Medicine Elsevier Health Sciences
• Livesey, M. A., Little, C. B., Boyd, C. (1991) Fatal hemorrhage associated with incarceration of small intestine by the epiploic foramen in three horses Canadian Veterinary Journal 32:434-436
• Mair, T. S., Love, S., Schumacher, J., Watson, E. (1998) Equine Medicine, Surgery and Reproduction WB Saunders
• Mair, T. S. (2003) Incarceration and impaction of a short segment of ileum into the epiploic foramen in a horse Equine Veterinary Education 15 (4) 189-191
• Orsini, J. A., Divers, T. (2007) Equine Emergencies: Treatment and Procedures Elsevier Health Sciences
• Radostits, O. M., Arundel, J. H., Gay, C. C. (2000) Veterinary Medicine: a textbook of the diseases of cattle, sheep, pigs, goats and horses Elsevier Health Sciences

Medical Treatment of Colic in Horses