The caecocolonic junction in humans has a sphincteric anatomy and function.

Sphincteric anatomy and function are present at the caecocolonic junction in several mammals. In humans, radiologists and endoscopists have respectively reported a circumferential contraction and a prominent ileocaecal fold at the border area between the caecum and the ascending colon. Anatomical findings on necropsy material failed to confirm its presence. Microscopic studies on surgical specimens showed the existence of muscular and innervational patterns different from those of adjacent areas. The aim of this work was to confirm the existence of a specialised fold at the caecocolonic junction in humans and to ascertain its role by carrying out a study of functional anatomy. Pancolonoscopies were performed on 100 patients and ileocaecal fold behaviour was observed before and after mechanical stimulation. Isolated ileocaecocolonic regions, surgically obtained, were filled with a fixative solution to study their macro and microscopic morphology after stimulation. Endoscopically, the ileocaecal fold was semilunar or circular in shape and spontaneous or evoked spasms occurred in 52 patients. A prominent circular fold could be seen in surgical specimens after stimulation. The entire muscle coat deeply penetrated this fold, showing the features characteristic of the ileocaecal junction. In particular, the inner portion of the circular muscle showed a peculiar arrangement and was thicker than elsewhere. These results show that in humans the caecocolonic junction is provided with a sphincter morphology and function. Little is known about its physiological relevance in ileal flow accommodation and caecal filling and emptying but it should not be underestimated with regard to some colonic motility disorders.