SUMMARY
When the development of the mullerian duct is normal on one side, but imperfect on the other side , a lateral fusion defect often with obstruction ,described as rudimentary horn,is produced. Most rudimentary horn are non functional and some are attached to the functioning contralateral horn by means of fibrous bands. If the endometrium lining the cavity of the non communicating rudimentary horn is is functional ,retention of menstrual blood causes cyclic abdominal pain and spillage of blood into the abdominal cavity via the tubal ostium may lead to endometriosis.Sometimes a narrow communicating channel exists between the rudimentary horn and the opposite uterine cavity.Under these circumstances pregnancy is possible,most of the patients present with symptoms suggestive of an ectopic pregnancy including of uterine rupture causing catastrophic bleeding and circulatory collapse.We present a similar case where laparotomy was done thinking of ruptured ectopic pregnancy.