The terminal ileum is the most distal segment of small bowel. It immediately precedes the small bowel's connection with the colon through the ileocaecal valve. It is of particular interest since a number of infectious and inflammatory processes preferentially involve the segment.
- location: the most distal ileum, ~30 cm proximal to the ileocaecal valve
- blood supply: branches of the ileocolic artery, including the ileal branch of ileocolic artery and the recurrent ileal artery
Relations and/or Boundaries
Although the terminal ileum is more or less considered the 30 cm of ileum that precedes the ileocaecal valve and caecum, it can also be thought of as a functional definition; the portion of distal ileum that is more lymphatic-rich than the rest of the ileum.
- ileal branch of ileocolic artery
- recurrent ileal artery
- accompany the respective arteries and drain into the superior mesenteric vein
- lymphatic aggregates are more dense in this segment than elsewhere in the ileum
Except in cases of intestinal malrotation, the terminal ileum is located in the right lower quadrant on imaging.
Small bowel follow through (SBFT)
- circular folds are sparse in the terminal ileum and the mucosa can sometimes appear essentially featureless
- normal ultrasound gut signature
- the terminal ileum can occasionally be mistaken for the appendix, but the terminal ileum is not blind-ending and usually is peristalsing
CT and MR enterography
- located in the right lower quadrant
- appears similar to other ileal loops unless inflamed
- circular folds are more sparse in this segment than in other segments of the ileum
In addition to more general disorders involving the small bowel, the lymphatic-rich terminal ileum is a common target of some infectious organism and some generalised inflammatory processes
In addition, because of its location immediately preceding the colon, it can be involved with colonic processes as well
False-positive evaluation for inflammatory bowel disease in the terminal ileum on fluoroscopy may be due to underdistention or lymphoid nodular hyperplasia.
- 1. Gray's Anatomy. Churchill Livingstone. (2011) ISBN:0443066841. Read it at Google Books - Find it at Amazon
- 2. Skandalakis LJ. Surgical Anatomy. P.M.P. ISBN:9603990744. Read it at Google Books - Find it at Amazon
- 3. Plumb AA, Pendsé DA, McCartney S et-al. Lymphoid nodular hyperplasia of the terminal ileum can mimic active crohn disease on MR enterography. AJR Am J Roentgenol. 2014;203 (4): W400-7. doi:10.2214/AJR.13.12055 - Pubmed citation