Infracolic Compartment

compartimentum infracolicum

The infracolic compartment is the portion of the peritoneal cavity below the transverse mesocolon, containing the small bowel loops, the ascending and descending colonic segments (below the transverse colon), and the sigmoid colon. It is divided by the root of the mesentery into right and left infracolic spaces.

Anatomical Data

Boundaries & Contents

Location	Lower abdomen, the part of the peritoneal cavity below the transverse mesocolon
Boundaries	Transverse colon and mesocolon (above) Root of the small bowel mesentery (divides it into right and left spaces) Ascending and descending colon (sides) Pelvic inlet (below; the left space opens freely into the pelvis)
Contents	Small intestine Peritoneal fluid

Biomechanics

Function & Actions

Holds the coils of small intestine. The slope of the mesentery root steers fluid in the right space toward the right iliac fossa and in the left space toward the pelvis.

Clinical Relevance

Clinical Notes

The infracolic compartment is the primary site of small bowel perforation, mesenteric ischaemia, and peritonitis. In laparoscopy, the infracolic space is entered after dividing the gastrocolic omentum. Free fluid in the infracolic compartment on FAST ultrasound indicates bowel injury or mesenteric vessel haemorrhage. The right infracolic space communicates with the right paracolic gutter and pelvis, making it the route of abscess spread from appendicitis.

Pathology

Common Injuries & Conditions

Infracolic Peritonitis

Infection spreading through the infracolic compartment from small bowel perforation or mesenteric ischaemia, producing generalised abdominal rigidity and requiring emergency laparotomy.

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