Catamenial appendicitis.

BACKGROUND: Reproductive-aged women undergoing appendectomy for suspected appendicitis have twice the rate of negative histology as age-matched men. The reason for this discrepancy is unknown.

CASES: Three patients with peritoneal endometriosis and recurrent symptoms of acute appendicitis coincident with menses underwent resection of a noninflamed appendix with long-term symptom resolution. Standard pathological evaluation failed to demonstrate evidence of appendiceal endometriosis or appendicitis. Additional evaluation demonstrated a marked increase in number of mast cells in the appendiceal muscularis compared with normal appendices.

CONCLUSION: The term "catamenial appendicitis" has been coined to describe these cases, and a mechanism of pathogenesis of right lower quadrant pain and nausea in patients with histologically confirmed endometriosis is proposed.