Parts
- Duodenum: cranial part from the pylorus, cranial flexure, descending duodenum along the right side of the abdomen, caudal flexure and ascending duodenum to the duodenojejunal flexure. The bile duct, already joined by the main pancreatic duct, opens at the major duodenal papilla.
- Jejunum: the longest part; its mobile loops, suspended from the mesentery, fill the middle and ventral abdomen. The jejunal lymph nodes lie at the root of the mesentery.
- Ileum: short final segment with a thicker muscular layer, opening into the colon at the ileocolic orifice next to the small caecum.
Clinical relevance
- Alimentary lymphoma: small cell (low-grade) lymphoma is the most common form of lymphoma in older cats. Telling it apart from inflammatory chronic enteropathy requires biopsy, often with immunohistochemistry and clonality testing.
- Ultrasound: the normal wall measures about 2–2.5 mm, slightly more in the ileum, whose prominent muscular layer gives a wagon-wheel appearance in transverse section. A thickened muscular layer suggests enteropathy or lymphoma.
- Linear foreign bodies: threads and ribbons pleat the loops ("plication") and can perforate the mesenteric border.
- Radiography: a loop diameter above about 12 mm in the cat suggests obstruction.
- Feline infectious peritonitis: can form focal granulomatous masses, especially in the ileocaecocolic region.
- Triaditis: concurrent inflammation of the small intestine, pancreas and biliary tract.
3D model
Intestinal loops segmented from the CT of a cat (pixelbeaker model), with the descending duodenum, simplified and registered to the atlas skeleton. The segments are not separated.