A study of an anatomic-physiological cecocolonic sphincter in humans.

We hypothesized an anatomical/physiological sphincter and investigated this hypothesis in current communication. The histomorphologic and morphometric studies were carried out in 14 cadavers and radiologic studies in 20; endoscopy studies were done in 16 healthy volunteers. Longitudinal sections along cecum, cecocolonic junction, and ascending colon were stained with H & E and Masson's trichrome stain. Morphometry study of musclethickness of cecum, cecocolonic junction, and ascending colon, radiological examination by method of small bowel barium meal administration, and endoscopic study by pancolonoscopy were studied. A cecocolonic fold was identified 2-2.5 cm distal to ileocecal nipple. It extended along gut circumference, shelf-like, and was marked by a shallow groove on outer aspect of colon. Microscopically, cecocolonic fold consisted of mucosa, submucosa, and muscularis externa. The circular muscle layer was thicker than that of cecum or ascending colon. Branching cells with ovoid nuclei representing probably intestinal cells of Cajal were identified in muscularis externa. Also morphometric study showed that circular muscle layer was significantly thicker than that of cecum or ascending colon, whereas longitudinal muscle exhibited no significant difference. Radiologic studies demonstrated narrowing at cecocolonic junction, which became wider on cecal contraction and narrower or closed on colonic contraction. Endoscopically, cecocolonic junction was narrow due to presence of cecocolonic fold, which exhibited spontaneous contractions. Our findings suggest an "anatomic" sphincter at cecocolonic junction as evidenced histomorphometrically, radiologically and endoscopically. Detection of interstitial cells of Cajal in cecocolonic fold postulates possible existence a pacemaker in cecocolonic fold, a point that needs further study.