EP20.01: Tail gut cyst masquerading as endometriosis: case report

Tail gut cysts (TGC) are a rare developmental anomaly, due to the remnant embryonic hindgut. Symptomatic TGC can be challenging to diagnose and manage. There are only scant reports in published literature. We report two cases of TGC diagnosed in our practice. We identified two cases of TGC diagnosed by ultrasound examination at Perth Obstetrics and Gynecology Ultrasound. The diagnosis was confirmed with additional imaging and or at surgery. We identified two cases of TGC over a 12 month period. Both were referred for pelvic pain symptoms with a suspicion of endometriosis in a 35 and 29 year old nulliparous females. Initial modality of investigation was trans-vaginal sonography that was successful in identifying the TGC as cystic lesions with low-level internal echoes mimicking endometriomas, related to posterior wall of the rectum. Sonovaginography done in both the patients confirmed the suspicion of TGC and also ruled out any identifiable foci of deep infiltrating endometriosis. Tumours around the sacrum are unusual and those occurring ventral to the sacrum are uncommon, particularly in adults. Two major embryologic structures, the tail gut and the neurenteric canal, have been proposed as the source of these cysts. TGC manifest with a variety of symptoms including constipation, pelvic pain, dysuria and dyspareunia in middle-aged women. Most cysts can be palpated clinically. In our small series of two cases, the use of specialised focused trans-vaginal ultrasonography was successful in detecting this rare entity. We wish to highlight the fact that in our series, the presentation, clinically mimicked endometriosis. TGC can mimic endometriosis in females. TV sonography is a valuable tool in correctly identifying TGC.