Presence and distribution of sensory nerve fibers in human peritoneal adhesions

Objective To assess the distribution and type of nerve fibers present in human perito neal adhesions and to relate data on location and size of nerves with estim ated age and with clinical parameters such as reports of chronic pelvic pai n. Summary Background Data Peritoneal adhesions are implicated in the cause of chronic abdominopelvic pain, and many patients are relieved of their symptoms after adhesiolysis. Adhesions are thought to cause pain indirectly by restricting organ motion, thus stretching and pulling smooth muscle of adjacent viscera or the abdom inal wall. However, in mapping studies using microlaparoscopic techniques, 80% of patients with pelvic adhesions reported tenderness when these struct ures were probed, an observation suggesting that adhesions themselves are c apable of generating pain stimuli. Methods Human peritoneal adhesions were collected from 25 patients undergoing lapar otomy, 20 of whom reported chronic pelvic pain. Tissue samples were prepare d for histologic, immunohistochemical, and ultrastructural analysis. Nerve fibers were characterized using antibodies against several neuronal markers , including those expressed by sensory nerve fibers. In addition, the distr ibution of nerve fibers, their orientation, and their association with bloo d vessels Were Investigated by acetylcholinesterase histochemistry and dual immunolocalization. Results Nerve fibers, identified histologically, ultrastructurally, and immunohisto chemically, were present in all the peritoneal adhesions examined. The loca tion of the adhesion, its size, and its estimated age did not influence the type of nerve fibers found. Further, fibers expressing the sensory neurona l markers calcitonin gene-related protein and substance P were present in a ll adhesions irrespective of reports of chronic abdominopelvic pain. The ne rves comprised both myelinated and nonmyelinated axons and were often, but not invariably, associated with blood vessels. Conclusions This study provides the first direct evidence for the presence of sensory n erve fibers in human peritoneal adhesions, suggesting that these structures may be capable of conducting pain after appropriate stimulation.