Preferential infiltration of large bowel endometriosis along the nerves of the colon

BACKGROUND: Little is known about the mode and the extent of infiltration of endometriotic lesions in the large bowel. METHODS: In 31 patients undergoing large bowel resection for severe deep-infiltrating endometriosis of the sigmoid and rectum with severe digestive symptoms, we performed a prospective morphological, histological and immunohistological study (using the monoclonal antibodies S100 for the detection of the nerves and CD10 for the detection of the endometriotic stromal cells) on the large bowel resection specimen. The evaluation of invasion of the large bowel by endometriosis was performed by studying the presence, localization and mean number of lesions in the different layers of the colon, the relationship between endometriosis and the nerves of the colon, the nerve density in the respective layers of the large bowel and the presence of endometriosis on the resection margins. RESULTS: The most richly innervated layers of the large bowel are the most intensely involved by endometriosis. We found that 53 +/- 15% of endometriotic lesions were in direct contact the nerves of the colon by means of perineurial or endoneurial invasion. The mean largest diameter of the lesion does not seem to be correlated with the depth of infiltration. The margins were positive in 9.7% of cases. In cases of positive margins, the endometriotic lesions were in close histological relationship with the nerves. CONCLUSIONS: There is a close histological relationship between endometriotic lesions of the large bowel and the nerves of the large bowel wall. Endometriotic lesions seem to infiltrate the large bowel wall preferentially along the nerves, even at distance from the palpated lesion, while the mucosa is rarely and only focally involved.