tailgut cysts , also known as retrotrectal cystic hamartomas , are rare congenital developmental lesions arising from postnatal primitive gut remnants , that generally occur in the retrorectal space , but have also been described in prerectal and perirenal locations . the retrorectal space is a potential space bound anteriorly by the mesorectum and posteriorly by the sacrum . the superior border is formed by the peritoneal reflection while the inferior border is formed by the rectosacral fascia . the lateral borders of the retrorectal space are formed by the ureters , the iliac vessels , the sacral nerve roots , and the lateral stalks of the rectum . the retrorectal space contains loose connective tissue , the middle sacral , iliolumbar and middle hemorrhoidal vessels , branches of the sympathetic and parasympathetic nervous systems , and lymphatics . the anatomical position and rarity of the lesion lead to difficulty first in diagnosis ( the lesion is often misdiagnosed ) and second in surgical management ( the condition is often suboptimally managed ) . these tailgut cysts predominantly occur in women , with average age of presentation at 35 years . rertrorectal tumors are frequently asymptomatic and are found incidentally during evaluation for unrelated physical complaints . half of the patients present with symptoms such as low back or rectal pain , pain during defecation , rectal bleeding , urinary frequency , etc . furthermore , retrorectal lesions in women can mimic gynecological pathology , and the risk of malignant transformation of a tailgut cyst always exists . despite that , the role of preoperative biopsy for retrorectal tumors is very controversial , but most authors agree that it can be a more harmful than a useful option . this is why preoperative high - resolution modern imaging techniques ( pelvic computed tomography [ ct ] or magnetic resonance imaging [ mri ] ) play such a crucial role in differential diagnostics between retrorectal tumors and planning the surgical management of retrorectal lesions , including tailgut cysts . complete surgical resection with negative margins still remains the cornerstone of surgical treatment , as this eliminates the potential of recurrence , hemorrhage , infection , compression , and malignant changes . a 40-year - old female was referred to our institution with the history of lower back swelling since 2 years . she consulted a surgeon , at some regional hospital , about 1 year back , who misdiagnosed it to be an abscess . the swelling was subjected to incision and drainage , at that regional hospital , but without any success . later on , the patient was referred to us , ultrasonography for pelvic organs demonstrated ill - defined large cystic lesion 8 cm  7 cm , posterior to the uterus . the margins could not be well defined due to distal acoustic shadowing of adjacent gut loops . a lumbosacral contrast - enhanced ct ( cect ) [ figures 1 and 2 ] , demonstrated a well - defined fluid density mass / collection with enhancing walls in the retrorectal , presacral , precoccygeal area , measuring ( 7.9 cm  11.2 cm  11.5 cm ) , with anterolateral displacement of rectum to left side , extending posterior to sacrum and coccyx through the infracoccygeal region forming a fluid collection with enhancing walls ( 4.5 cm  4.8 cm  13.5 cm ) . cect report suggested the lesion most likely to represent tailgut duplication cyst / retrorectal cystic hamartoma . bilobed retrorectal cyst axial view of retro - rectal / tailgut cyst following discussion , it was decided that surgical excision of this lesion was the most appropriate course of action given its symptomatology and uncertain malignant potential . a vertical incision was given over the swelling on the sacrococcygeal area , facilitated en bloc removal of the sacrococcygeal cystic mass [ figures 3 and 4 ] . the peritoneum overlying the pelvic brim was incised posterolaterally , and the mesorectal plane was entered . the rectum was fully mobilized , allowing the cyst , which was adherent to it , to also be mobilized and removed intact . previous scar of incision and drainage , and mucoid color fluid on aspiration of cyst surgical excision of cyst from the posterior approach histopathology revealed a multiloculated tailgut cyst containing abundant mucoid material lined by glandular mucinous epithelium with fibrous tissue and showing intestinal glands [ figure 5 ] , with no evidence of malignancy . she remains well at 1-year follow - up with no evidence of recurrence on serial pelvic imaging . histopathology showing intestinal glands within cyst wall confirming tailgut cyst ( h and e , 100 ) embryologically , tailgut cysts are believed to arise from vestigial remnants of the embryonic hindgut . the largest reported case series of 53 tailgut cysts over a 35-year period from 1950 to 1985 was described by hjermstad and helwig . they found that these cysts predominantly occurred in women ( female to male ratio , 3:1 ) . the ages ranged from 4 days to 73 years with an average age of presentation at 35 years . symptoms only occur due to the local mass effect on surrounding organs ( rectal fullness , constipation , painful defecation , lower abdominal and/or back pain or genitourinary obstruction ( dysuria ) ) , infection ( cysts with secondary infection have typical symptoms of anorectal or pelvic abscess and fistula , or perianal sinus ) , bleeding or malignant transformation / degeneration ( pain in the anorectal region ) . retrorectal cystic hamartomas in the presacral space are usually well - defined , thin - walled and multicystic or unilocular . despite the fact that the majority of tailgut cysts are benign , and can very rarely undergo malignant transformation and then most common histopathologic diagnoses are adenocarcinoma or carcinoid . they were lined by a variety of epithelia which varied not only among multiple cysts of multicystic lesions but also within the same cyst . the contents varied from clear fluid to dense mucous . due to the location of tailgut cysts , almost all of them are palpable on rectal examination as extrinsic , contained ; fluctuant masses . the differential diagnoses can be classified as congenital , neurogenic , osseous , miscellaneous , and inflammatory . excluding inflammatory processes , congenital lesions account for approximately two - thirds of retrorectal lesions . these include developmental cysts , chordomas ( remnants of notochord ) , and anterior sacral meningoceles . developmental cysts can be further divided according to their origin and histopathological features into tailgut cysts , enteric duplication cysts , dermoid cysts , epidermoid cysts , and teratomas . plain films , for investigation of presacral masses , are of limited use but may show evidence of bony destruction suggesting malignancy or an osseous lesion . rarely , they may identify a sacrococcygeal anomaly associated with tailgut cysts . transrectal ultrasound may be useful in demonstrating the integrity of the layers of the rectum as well as revealing a cystic lesion and clarifying whether it is unilocular or multilocular . the appearance of a tailgut cyst on ct imaging is usually of a well - defined , thin - walled , uni- or multi - locular , nonenhancing lesion in the retrorectal space . calcification does not tend to be a feature of tailgut cysts but has been reported and if present may suggest the possibility of malignancy . in our case , we did not get mri scan done as it was quite obvious on ct scan . mri has become the modality of choice to image tailgut cysts because of its multiplanar imaging capability ( allowing imaging of surgically relevant planes ) as well as its good soft tissue contrast . mri typically demonstrates a retrorectal lesion with low signal intensity on t1-weighted images and high signal intensity on - t2 weighted images although this may vary depending on cyst content . malignancy is suspected if there is focal irregular wall thickening and intermediate signal intensity before contrast on both t1- and t2-weighted images with enhancement after contrast . historically , the classical treatment in this area consists of different approaches : the anterior ( transabdominal ) , the posterior approaches ( inter - sphincteric , trans - sphincteric parasacrococcygeal , trans - sacral , trans - sacrococcygeal , trans - anorectal , and transvaginal ) . in the current case , combined approach ( posterior and then trans - abdominal ) was undertaken as the lesion could not be removed solely from posterior approach due to large retrorectal component and adhesions with the rectum . on follow - up , the patient was relieved of discomfort , constipation , and swelling . patient has been advised to visit hospital 36 monthly for the 1 year and yearly after that or if any fresh complaints appear . there is no standard recommendation for the follow - up of tailgut cysts in the literature . follow - up of this rare condition should , therefore , be clinical and case specific . if the patient develops symptomatology , targeted cross - sectional imaging should be instituted . in the presence of abnormal histology , serial perineal examination , and cross - sectional imaging are advised . the anatomical position and rarity of the tailgut cyst lead to difficulty firstly in diagnosis ( the lesion is often misdiagnosed ) and secondly in surgical management ( the condition is often suboptimally managed ) . surgical excision is the treatment of choice for tailgut cysts as this provides a definitive diagnosis , relieves symptoms , and prevents possible complications such as infection , fistula formation , and malignant degeneration . preoperative imaging with ct or mri is essential to plan the most appropriate surgical approach . one should be very alert while separating cyst from the rectal wall so as to prevent inadvertent injury to the rectum .