Intestinum tenue (Ileum et Jejunum)
The jejunum and ileum form the majority of the small intestine's length. The jejunum (~20 m) is the principal site of enzymatic digestion and nutrient absorption, with an enormous mucosal surface area created by plicae circulares and intestinal villi. The ileum (~30 cm) terminates at the ileocecal valve, marking the transition to the hindgut fermentation chamber. These segments are suspended by the extensive mesentery, supplied by the cranial mesenteric artery; the vessel most commonly affected by Strongylus vulgaris larval migration.
This segment represents the mid-to-distal small intestine (jejunum and ileum). The ileocecal junction is a critical anatomical landmark palpable per rectum. Anoplocephala perfoliata tapeworms cluster at this junction and are implicated in ileal impaction, intussusception, and spasmodic colic.
Small intestine herniates through the epiploic foramen and becomes strangulated.
Pedunculated fatty tumor wraps around small intestine, cutting off blood supply. Common in older horses.
Obstruction of the ileum, often from coastal Bermuda grass hay.
Inflammation of the proximal small intestine causing massive fluid sequestration.
Rotation of the small intestine causing strangulation.
Telescoping of one segment of jejunum into an adjacent segment, causing obstruction and ischemia. More common in young horses and may be associated with tapeworm (Anoplocephala perfoliata) infection.
Abscess formation in the mesenteric root, often secondary to Streptococcus equi (strangles) or migrating Strongylus vulgaris larvae. May cause intestinal adhesion or strangulation.
Bacterial infection causing thickening of the small intestinal wall in weanlings (4-8 months). Increasingly recognized as a cause of hypoproteinemia in young horses.
Small intestine herniates through the epiploic foramen and becomes strangulated. Signs include: Acute severe colic; nasogastric reflux; rapid deterioration; surgical emergency
Pedunculated fatty tumor wraps around small intestine, cutting off blood supply. Common in older horses. Signs include: Acute severe colic; nasogastric reflux; rapid heart rate; typically horses >15 years old
Obstruction of the ileum, often from coastal Bermuda grass hay. Signs include: Moderate to severe colic; small intestinal distension on ultrasound; decreased fecal output
Inflammation of the proximal small intestine causing massive fluid sequestration. Signs include: Depression; large volumes of nasogastric reflux; dehydration; laminitis risk; fever
Rotation of the small intestine causing strangulation. Signs include: Severe acute colic; rapid deterioration; nasogastric reflux; surgical emergency
Telescoping of one segment of jejunum into an adjacent segment, causing obstruction and ischemia. More common in young horses and may be associated with tapeworm (Anoplocephala perfoliata) infection. Signs include: Acute colic; nasogastric reflux; distended loops of small intestine on ultrasound; target-like lesion on ultrasound cross-section
Abscess formation in the mesenteric root, often secondary to Streptococcus equi (strangles) or migrating Strongylus vulgaris larvae. May cause intestinal adhesion or strangulation. Signs include: Recurrent colic; weight loss; intermittent fever; palpable abdominal mass per rectum in some cases
Bacterial infection causing thickening of the small intestinal wall in weanlings (4-8 months). Increasingly recognized as a cause of hypoproteinemia in young horses. Signs include: Rapid weight loss; ventral edema; diarrhea (variable); pot-bellied appearance; low serum albumin and total protein
This segment represents the mid-to-distal small intestine (jejunum and ileum). The ileocecal junction is a critical anatomical landmark palpable per rectum. Anoplocephala perfoliata tapeworms cluster at this junction and are implicated in ileal impaction, intussusception, and spasmodic colic.
See the Small Intestine (Ileum/Jejunum) on our interactive 3D horse model. Open 3D Model