Abstract A case of non-communicating rudimentary uterine horn is presented and is a characteristic example of the way that surgical treatment can exacerbate dysmenorrhea by blocking retrograde menstruation. There is always some risk of missing the true diagnosis in cases of uterine abnormalities, even by direct inspection, but intraoperative laparoscopic ultrasonography can be an invaluable tool in defining anatomy. As laparoscopic resection has become the standard procedure for the treatment of unicornuate uterus, laparoscopic ultrasonography can be a useful tool for providing anatomical information to the operating surgeon about the patient.