caecocolonic junction and sphincter in man: morphological, radiological and endoscopic study

ABSTRACT

Histomorphological and morphometric studies were carried out in 15 cadavers, radiological study was performed in 20 and endoscopic study in 16 healthy volunteers. Longitudinal histological sections along the caecum, the caecocolonic junction and the ascending colon were stained with hematoxylin and eosin as well as Masson's trichrome. The morphometric study determined the thickness of the muscle layers of the caecum, the caecocolonic junction and the asending colon using image analyser computer equipment. The caecocolonic junction was also examined radiologically by the method of small bowel barium meal follow through as well as endoscopically by pancolonoscopy. A caecocolonic fold was identified at 22-31 mm distal to the ileocaecal valve. It extended along the gut circumference and was shelf-like and marked by a shallow groove on the external aspect of the colon. Microscopically, the caecocolonic fold consisted of mucosa, submucosa, muscularis externa and serosa, all of which were a continuation of those of the caecal wall. The circular muscle layer of this fold was thicker than that of each of the caecum and the ascending colon. Branching cells with ovoid nuclei representing probably interstitial cells of Cajal were identified in the muscularis externa. The morphometric study also showed that the circular muscle layer was very highly significantly thicker than that of the caecum or the ascending colon [p < 0.001 and p < 0.001, respectively] while the longitudinal muscle layer exhibited no significant difference [p > 0.05 and p > 0.05, respectively]. Radiological study demonstrated narrowing at the caecocolonic junction which decreased on caecal contraction and increased or closed on ascending colonic contraction. Endoscopically, the caecocolonic junction was narrow due to the presence of the caecocolonic fold and sphincter which exhibited spontaneous contractions. In conclusion, the present study suggests the presence of an anatomical sphincter at the caecocolonic junction as evidenced histomorphometrically, radiologically and endoscopically. The muscularis externa was significantly thicker than that of each of the caecum and the ascending colon. Spasmodic contractions of the caecocolonic fold were observed on endoscopic examination. Radiological study showed dilatation and narrowing of the caecocolonic junction on caecal and ascending colon contraction, respectively. Absence of colocaecal reflux on colonic contraction is probably due to contraction of the caecocolonic sphincter. The detection of cells similar to the interstitial cells of Cajal, in the caecocolonic fold, postulates the possible existence of a pacemaker in the caecocolonic fold; a point that needs further investigation