Iliac fossa

Recommended video: Bony pelvis [27:56]

Overview of the bony pelvis.

The Iliac fossa is a large depression on the anteromedial aspect of the flat, fan-shaped upper part (ala or wing) of the iliac bone (ilium). It forms the posterolateral wall of the greater (false) pelvis.

The iliac fossa is limited superiorly by the iliac crest and anteriorly by the anterior border of the ilium. A medial border, located posteriorly, separates the iliac fossa from the sacropelvic surface of the ilium, which bears an articular surface for the sacrum. The iliac fossa terminates inferiorly at a ridge on the medial surface of the ilium called the arcuate line.

The smooth and concave iliac fossa serves as the proximal surface of attachment for the iliacus muscle, which occupies the entire fossa.

The term iliac fossa can also be used to describe the two lower lateral regions of the abdomen (right and left iliac fossae), which overlie the iliac fossae of the iliac bones, when the abdomen is divided into nine regions. This division of the anterior abdominal wall using the subcostal, transtubercular and two paramedian planes enables clinicians to describe the locations of abdominal pain or tenderness, masses, lesions, or the position of abdominal organs. The right iliac fossa region typically contains the cecum, vermiform appendix and the terminal ileum while the left iliac fossa region holds the distal part of the descending colon and the proximal sigmoid colon.