What are haustra?
The longitudinal muscle layer of the colon is divided into three thick bands, termed the taeniae coli . There is a paucity of longitudinal muscle between the three tenial bands. Haustra are sacculations of colon protruding between the three rows of taeniae coli. At the edges of the haustral sacculations, folds, termed interhaustral folds , radiate toward the taeniae coli. The colon is identified by its haustral sacculations and interhaustral folds on any radiologic study—whether plain abdominal radiograph, computed tomography (CT), magnetic resonance imaging (MRI), or barium enema. Rounded, air-filled pockets are seen in a nondependent (anterior) position. Fluid-filled or contrast-filled rounded sacculations are seen on the dependent (inferior) surface.
Haustra are relatively fixed structures in the right and transverse colon. Haustra are intermittently seen structures in the descending and proximal sigmoid colon, depending on the stage of colonic contraction. The left colon may intermittently appear “ahaustral,” depending on the degree of colonic contraction. Although the edge of the colon has a sacculated appearance, the edge of the small bowel is relatively straight, altered only by its thin valvulae conniventes. Valvulae conniventes are thinner than interhaustral folds and cross the entire lumen of the bowel, whereas interhaustral folds cross about one third of the colonic diameter when seen in profile. Seen en face, the interhaustral folds may falsely appear to cross the entire lumen of the colon.