Tailgut duplication cysts, also known as retrorectal cystic hamartomas, are rare congenital lesions that are thought to arise from vestiges of the embryonic hindgut.
There is a recognized strong female predilection. While it can present at any age, presentation is usually at around 30-60 years of age 4.
Many lesions are discovered incidentally 5. Approximately 50% of patients may have perirectal symptoms, likely pelvic pain and constipation 9,10.
On gross pathological examination, a tailgut cyst is usually comprises a multiloculated, cystic mass with a thin wall and glistening lining and is filled with a mucoid material. The cysts can be lined by a variety epithelial cells, including ciliated columnar, mucin-secreting columnar, transitional, and squamous epithelium 10.
The lesions usually measure several centimeters in diameter. Occasionally, a sacral bone defect and/or associated calcifications may be present 3.
It is almost exclusively found in the retrorectal or presacral space and very rarely in other sites such as the perirenal area or the subcutaneous tissues 7.
Transrectal ultrasound may show a multilocular, retrorectal cystic mass. Internal echoes may be found within the cyst due to the multi-cystic nature of the mass and the presence of gelatinous material or inflammatory debris within the cyst.
Often seen as a discrete, well-marginated, presacral mass with water or soft-tissue density, depending on the contents of the cyst. Calcifications may be seen in the cyst wall. When the mass is large, the rectum is displaced by the mass. If concurrent infection or malignant transformation occurs, CT may reveal loss of discrete margins and involvement of contiguous structures.
MRI signal characteristics depend on whether the cyst is complicated or not. Complications include:
- infection or inflammation
- malignant change: rare and concerning potential complication 1
- T1: low signal
T2: high signal
- some reports suggest that a multilocular appearance with internal septa on T2 images to a cyst in the retrorectal region is a feature unique to tailgut duplication cysts 6
- T1: high signal components may occur due to the presence of mucinous material, high protein content, or associated intracystic hemorrhage
- T2: low signal components may occur due to the presence of hemorrhage or associated keratin 4
Treatment and prognosis
While uncomplicated cysts are benign, surgical excision is the recommended treatment of choice even in asymptomatic cases, especially because of potential complications 3-5.
General imaging differential considerations for a cystic lesion in the retrorectal region are rather broad and include 3,8:
- other developmental cysts in the retrorectal region
- cystic sacrococcygeal teratoma
- anterior sacral meningocele
- anal duct cyst: anal gland cyst
- necrotic rectal leiomyosarcoma
- extraperitoneal adenomucinosis
- cystic lymphangioma in the retrorectal region
- retrorectal pyogenic abscess
- necrotic sacral chordoma
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