Blood may enter the peritoneal cavity in the perimenstrual period through patent fallopian tubes. It may be fairly common. The presence of menstrual blood in the peritoneal cavity can cause diagnostic problems during peritoneal dialysis or following trauma, resulting in unnecessary testing.


Features of retrograde menstruation:

(1) presence of blood in the peritoneal cavity during the perimenstrual period

(2) absence of blood at other times

(3) findings not explained by another cause


It is seen more often in women with patent fallopian tubes. In completely ligated tubes the proximal stumps may become filled with blood, which can cause dysmenorrheal (Morrissey et al).


Cervical stenosis may be a risk factor (Barbieri et al).


Differential diagnosis:

(1) bleeding from foci of endometriosis


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