pelvic pain results from many causes such as primary dysmenorrhea , uterine anomalies , menstrual outflow obstruction , endometriosis , myoma and adenomyosis . a 15-year - old nulligravida young woman with a history of severe intermittent pelvic pain presented a 4 - 5 centimeter mass . laparotomy revealed left rudimentary horn , non - communication was confirmed by postoperative hysterosalpingogram ( hsg ) and magnetic resonance imaging ( mri ) . rudimentary horn should be considered in differentiation of pelvic pain and mass in young females . dysmenorrhea is categorized as primary when no pelvic pathology is revealed and secondary when there is a known pathological source . characteristics of secondary dysmenorrhea include beginning of pain 7 - 14 days before menstruation , continuation of pain after menstruation , resistance to non - steroidal anti - inflammatory drugs and contraceptive pills . in case of secondary dysmenorrhea , uterine and vaginal anomalies , menstrual outflow obstruction , endometriosis , adenomyosis and uterine myoma are considered in the differential diagnosis ( 1 ) . some of the congenital abnormalities in the mullerian duct present with dysmenorrhea including imperforated hymen , cervical atresia , transverse septum of the vagina and rudimentary horn besides unicorn unite uterus . in imperforated hymen , complete absence of the cervix might result in pain and obstruction for which hysterectomy is necessary ( 3 ) . the incidence of mullerian duct malformation in the general population is estimated to be 43% while that of unicornuate uterus is about 0.4% ( 4 ) . in another study ultrasonography performed two months ago , revealed a mass of 4.5 centimeters in her left adnexa . another sonography described the mass as a 5 cm solid tumor in favor of uterine myoma on the left side . expert sonography of this center and color doppler velocimetry reported a 5.3 centimeters myoma on the left side with high vascular flow suggesting leiomyosarcoma or degenerated myoma . surgical findings revealed bilateral normal appearing ovaries . on the left side there was a solid mass with the fallopian tube connected superior to this mass and in a lower position in comparison to the right side . a rudimentary horn was considered . thus , a small incision was made on the mass extracting about 2 cm of chocolate fluid compatible with old blood . exploration of the cavity by a narrow metal applicator , showed a small cavity without an outflow pathway . at this stage , blue dye transit from fallopian tubes occurred without entry to the peritoneal cavity . due to no bilateral entrance of dye , while passing from tubes , technical problems was not ruled - out . in the operative field non - communication of the rudimentary horn biopsy of rudimentary mass and cavity was done for pathological review and surgical intervention was not taken . the treatment plan was the use of contraception while hysterosalpingography and mri were performed to achieve definite diagnosis before the next surgery . unfortunately the patient rejected surgery due to post - surgical pain relief resulting from evacuation of chocolate fluid . pathological report of mass biopsy suggested a " vascular myoma " and cavity biopsy reported " inactive endometrium " . hysterosalpingography ( hsg ) report indicated a right unicornuate uterus with normal right fallopian tube and normal peritoneal spillage . the other side of the rudimentary horn and fallopian tube was not shown by the hsg examination . the mri report about 1.5 month after the operation revealed a 4 cm mass on the left side of the uterus with a small central cystic blood - containing locus of about 1.1 cm . the patient accepted a third operation after menarche and resection of rudimentary horn and left fallopian tube was done about 10 months after the second surgery , due to recurrence of severe pain . uterine anomalies are rare and they are seldom considered in differential diagnosis of patients with clinical presentation of pelvic pain ( 6 ) . in the present case , uterine myoma was considered as the first diagnosis and uterine anomalies were not mentioned in differential diagnosis . most rudimentary horns are asymptomatic due to their non - functional and non - communicating pattern ( 3 ) . in the case of endometric development in rudimentary horn , menstrual fluid is produced and implantation of conception product might occur . thus , rudimentary horn pregnancy and pelvic pain occur . rudimentary horn pregnancy mimics the clinical presentation of ectopic pregnancy resulting in surgical emergency ( 7 ) . ultrasound revealed an empty uterus and free fluid in the abdominal cavity . in the laparotomy procedure , rudimentary another case report of ruptured rudimentary horn pregnancy at 19 weeks was by hassan et al . rudimentary horn pregnancy is visually miss - diagnosed until the occurrence of rupture and emergency . there is a case report on an asymptomatic 33-year - old pregnant woman who was diagnosed by laparoscopy - hysteroscopy following the diagnosis of ectopic pregnancy . in the laparoscopy , this case cooperated due to hysteroscopic and pre - rupture diagnosis . in our case , intraoperating dye injection was done , as well , although definite diagnosis was not done . as mentioned earlier , diagnosis of rudimentary horn is not made until the reproductive age when ruptured rudimentary horn pregnancy or pelvic pain occur . pain is due to endometrial response to hormonal activities after menarche . in the present case , her history included several surgical interventions and miss diagnosis with appendicitis and other entities . in the rare case of unicornete non - communicating horn , surgical resection is necessary to relief pain and prevent rudimentary horn pregnancy and resulting emergency situations ( 10 ) . surgery was done more than two years after menarche as the third surgical intervention . in the first surgery diagnosis was appendicitis due to pain . after the second surgical intervention definite diagnosis was made . due to transient pain relief after the second surgery , the patient and her family rejected definite surgery until she experienced severe pain again within 10 months . intraoperative limitation of case management ( in the second surgery ) was inability to show open tube on the right side , thus definite diagnosis and surgery at that stage was not possible . hysteroscopy was acceptable , although it was not done due to the inability to diagnose this case . rudimentary horn should be considered in cyclic pelvic pain starting after menarche besides a mass like lesion , sometimes mistaken by myoma . early diagnosis is needed to relief pain and prevent surgical emergency by rudimentary horn resection .
introduction : pelvic pain results from many causes such as primary dysmenorrhea , uterine anomalies , menstrual outflow obstruction , endometriosis , myoma and adenomyosis . 
 this study reports on a rare case of non - communicating functional rudimentary horn.case presentations : a 15-year - old nulligravida young woman with a history of severe intermittent pelvic pain presented a 4 - 5 centimeter mass . 
 a surgical procedure for appendicitis was previously performed on this patient . per - operative 
 diagnosis was myoma and suspicion of leismus sarcoma . 
 laparotomy revealed left rudimentary horn , non - communication was confirmed by postoperative hysterosalpingogram ( hsg ) and magnetic resonance imaging ( mri ) . 
 resection of mass and left fallopian tube was done during the second surgery.conclusions:rudimentary horn should be considered in differentiation of pelvic pain and mass in young females . early diagnosis and horn resection prevents emergency surgery and reliefs pain .