THE CAECOCOLONIC JUNCTION IN HUMANS HAS A SPHINCTERIC ANATOMY AND FUNCTION

Sphincteric anatomy and function are present at the caecocolonic junct ion in several mammals. In humans, radiologists and endoscopists have respectively reported a circumferential contraction and a prominent il eocaecal 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 existen ce of muscular and innervational patterns different from those of adja cent areas. The aim of this work was to confirm the existence of a spe cialised fold at the caecocolonic junction in humans and to ascertain its role by carrying out a study of functional anatomy. Pancolonoscopi es were performed on 100 patients and ileocaecal fold behaviour was ob served before and after mechanical stimulation. Isolated ileocaecocolo nic regions, surgically obtained, were filled with a fixative solution to study their macro and microscopic morphology after stimulation. En doscopically, the ileocaecal fold was semilunar or circular in shape a nd spontaneous or evoked spasms occurred in 52 patients. A prominent c ircular fold could be seen in surgical specimens after stimulation. Th e entire muscle coat deeply penetrated this fold, showing the features characteristic of the ileocaecal junction. In particular, the inner p ortion of the circular muscle showed a peculiar arrangement and was th icker than elsewhere. These results show that in humans the caecocolon ic junction is provided with a sphincter morphology and function. Litt le is known about its physiological relevance in ileal accommodation a nd caecal filling emptying but it should not be underestimated with re gard to some colonic motility disorders.