Study objective: To investigate the extent and types of innervation of endometriotic lesions in various regions of the bowel.
Design: Retrospective nonrandomized immunohistochemical study (Canadian Task Force classification II-3.
Setting: University-based laboratory.
Patients: Thirty-six women undergoing laparoscopy or laparotomy because of deep infiltrating endometriosis in various regions of the bowel, including the sigmoid colon, appendix, and rectum.
Interventions: Immunohistochemical staining of endometriotic specimens with antibodies against protein gene product 9.5, neurofilament, nerve growth factor, nerve growth factor receptors tyrosine kinase receptor A and p75, growth-associated protein 43, substance P, neuropeptide Y, and vasoactive intestinal peptide to demonstrate myelinated, unmyelinated, sensory, and autonomic nerve fibers.
Measurements and main results: There were significantly more nerve fibers in intestinal deep infiltrating endometriosis (mean [SD] 172.6 [94.2]/mm(2)) than in other deep infiltrating endometriotic lesions (e.g., cul-de-sac and uterosacral ligament) (67.6 [65.1]/mm(2); p<.01). Intestinal deep infiltrating endometriosis was innervated abundantly by sensory Adelta,sensory C, cholinergic, and adrenergic nerve fibers. Nerve growth factor, tyrosine kinase receptor A, and p75 were strongly expressed in endometriotic lesions, and growth-associated protein-43 was also strongly expressed in the endometriosis-associated nerve fibers.
Conclusion: The hyperinnervation in intestinal deep infiltrating endometriosis may help to explain why patients with this type of lesion have more severe pain.