PERITONEAL ADHESIONS: They Appear to be Cellular, Innervated, and Vascularized Entities

Peritoneal adhesions are bands of fibrous tissue that join abdominal organs to each other or the abdominal wall. Adhesions develop rapidly after damage to the peritoneum during surgery, infection, trauma, or irradiation. Postoperative adhesion formation occurs in 93% to 100% of patients undergoing laparotomy, leading to complications such as intestinal obstruction and infertility in women. Adhesions have also been implicated as a cause of chronic abdominopelvic pain, and many patients have been relieved of their symptoms after adhesiolysis. Chronic pelvic pain accounts for up to 25% of all gynecologic visits, 30% to 50% of all diagnostic laparoscopic procedures, and approximately 5% of hysterectomies. In financial terms, the annual cost of resources for the diagnosis and treatment of women with chronic pelvic pain in the United Kingdom is approximately £600 million, and therefore the role of adhesions in pain etiology should be addressed. It has been proposed that peritoneal adhesions indirectly cause pain by restricting organ mobility or expansibility and thus stimulating stretch receptors in the smooth muscle of adjacent organs or the abdominal wall. However, mapping studies of reported pain using microlaparoscopic techniques showed that 80% of patients with significant pelvic adhesions reported tenderness when these structures were probed, suggesting that these structures can generate pain stimuli. The presence of nerve fibers in human pelvic and abdominal adhesions supports this theory. The aim of the present study was to characterize the type of nerve fibers found in human peritoneal adhesions using histologic, ultrastructural, and immunohistochemical techniques and to relate the findings to the location, size, and estimated age of the adhesions and clinical parameters such as reports of chronic pelvic pain. Nerve fibers were identified using antibodies directed against synaptophysin, a protein of synaptic vesicles, and the neuropeptides calcitonin gene-related peptide (CGRP), expressed by sensory nerves, and substance P, present in pain-conducting fibers. Fibers expressing vasoactive intestinal peptide (VIP), a marker for cholinergic sympathetic nerve fibers, and tyrosine hydroxylase (TH), an intermediary enzyme in catecholamine synthesis of adrenergic nerve fibers, were also identified.