Increased C-Reactive Protein Concentrations During Menstruation Are Important for the Pathophysiology of Endometriosis and Possibly Adhesion Formation. A Systematic Review

Objectives: Retrograde menstruation occurs in most women and could cause some peri-toneal irritation. The peritoneal cavity is a cavity outside the bloodstream, with a specific hormonal, immunological and microbiological micro-environment distinct from plasma. The mesothelial cells lining the peritoneal cavity react within seconds to minor trauma, such as blood, with retraction, causing acute inflammation and later inflammation. This mesothelial cell retraction exposes the basal membrane and facilitates implantation of tu-mour cells. The acute inflammation enhances adhesion formation after surgery, and causes pain. Design: A systematic review of menstrual C-reactive protein (CRP) concentrations, a non-specific marker of peritoneal inflammation (PROSPERO ID 536306). Results: All articles (n=8) showed a variable increase in CRP concentrations during the men-strual and early follicular phase of 80±36%. Conclusions: CRP concentrations are slightly increased during menstruation and the early follicular phase. This increase is likely due to retrograde menstruation, causing mesothelial cell retraction and acute pelvic inflamma-tion. It seems logical that the mesothelial cell retraction facilitates endometrial cell im-plantation and explains the anatomical distribution of endometriosis lesions. Acute pelvic inflammation may enhance postoperative adhesion formation.