Clinical Radiology (1992) 45, 288 289
Case Report: Tailgut Cyst-Assessment With Transrectal Ultrasound K_ A. R. H U T T O N and E_ A. B E N S O N
Department of Surgery, Leeds" General Infirmary, Leeds Tailgut cysts are derivatives of the embryonic post-anal gut. Usually asymptomatic, they are discovered in adult life as an incidental retrorectal mass. Complications include infection, with the formation of retrorectal abscesses and occasionally anal fistulae, and a long-term risk of malignant change, which means that once discovered surgical excision is advised. We present a case that was assessed pre-operatively with transrectal ultrasound. The findings were of a well defined cystic lesion, with no evidence of invasion. We believe that transrectal ultrasound is of value in assessing retrorectal lesions. Hutton, K.A.R. & Benson, E.A. (1992). Clinical
Radiology 45, 2 8 8 - 2 8 9 . C a s e R e p o r t : T a i l g u t C y s t - A s s e s s m e n t W i t h T r a n s r e c t a l U l t r a sound
T a i l g u t cysts are r a r e lesions o f d e v e l o p m e n t a l o r i g i n o c c u r r i n g in the r e t r o r e c t a l space. W e believe this is the first r e p o r t o f this u n u s u a l lesion b e i n g i m a g e d by t r a n s r e c t a l u l t r a s o u n d , a t e c h n i q u e g a i n i n g p o p u l a r i t y in the a s s e s s m e n t o f rectal a n d e x t r a r e c t a l disease.
CASE REPORT A 40-year-old woman presenting with anal fissure was found, incidentally at examination under anaesthesia, to have a retrorectal mass. Fine needle aspiration produced 5 ml of grey turbid fluid. Cytology was unremarkable. Before excisional surgery, a transrectal ultrasound was performed in the radiology department using a 5.5 MHz radial scanner (BrueI and Kjaer, Denmark). This revealed a 5 x 2 cm cystic extrarectal mass in the pre-coccygeal area. The lesion was well defined, producing deformity of the rectum without evidcnce of invzision. All layers of thc rectal wall were still visible and uninterrupted (Fig. 1). The mass was excised using a post-anal approach. She made an uneventful recovery, and was discharged on the fourth post-operative day. Exanfination of the resected specimen revealed a multicystic mass, circumscribed, which was not encapsulated. Histological examination showed the cysts to be lined with columnar epithelium, with areas of squamous metaplasia. Smooth muscle was found in the interstitial tissue, but no well developed muscle wall or neuraI plexus was seen, conforming with the pathological criteria of a tailgut cyst.
DISCUSSION T h e r e t r o r e c t a l space is a p o t e n t i a l a r e a w h o s e a n a t o m i c a l b o u n d a r i e s are the r e c t u m a n t e r i o r l y , the s a c r u m a n d c o c c y x p o s t e r i o r l y , the p e r i t o n e a l r e f l e c t i o n s u p e r i o r l y a n d the l e v a t o r ani and c o c c y g e u s m u s c l e s inferiorly. T h e iliac vessels a n d the ureters define its l a t e r a l m a r g i n s (Fig. 2). T h e first r e p o r t e d case o f a cystic m a s s in this r e g i o n was in a 1 - y e a r - o l d girl a n d p r o b a b l y r e p r e s e n t e d a rectal d u p l i c a t i o n ( M i d d e l d o r p f , 1885). S c a t t e r e d r e p o r t s since t h e n c o n f i r m t h e r a r i t y o f r e t r o r e c t a l cysts. In o n e series o f 20851 p r o c t o s c o p i e s , o n l y t h r e e s u c h m a s s e s w e r e disc o v e r e d ( S p e n c e r a n d J a c k m a n , 1962). M o s t r e t r o r e c t a l cysts p r e s e n t i n g d u r i n g a d u l t life are d e r i v a t i v e s o f the Correspondence to: Mr K. A. R. Hutton, Department of Paediatric Surgery, Clarendon Wing, Leeds General Infirmary, Belmont Grove, Leeds LS2 9NS.
Fig. 1 -Transrectal ultrasound showing the tailgut cyst (short arrows) posterior to and causing deformity of the rectal wall. The scan identifies five layers of the rectal wall of which the outer hypoechoic layer (long arrow) represents the muscularis propria.
i Retroreetal --
~ -
-
--~
Fig. 2-Anatomy of retrorectal space.
I space
TAILGUT CYST ASSESSMENT WITH TRANSRECTAL US
Hindgut \
Allantois- ~
l
ProctodeumTailgut. -.
Ii~_ Notochord - --Neural tube
=:
::.,: 5::::,,,: .........
Fig. 3 Caudal end of embryo, 4 mm stage.
embryonic tailgut (Hjermstad and Helwig, 1988). This structure is a portion of gut, distal to the future anus, present during the 3.5-8 m m stage of development when the embryo possesses a true tail (Fig. 3). Incomplete regression is said to give rise to cysts in the retrorectal space (Gius and Stout, 1938). These so-called tailgut cysts have an intestinal type of epithelial lining and no definite muscular or serosal coat (Caropreso et al., 1975). Squamous epithelium, present in 75% of cysts, may in some represent metaplasia secondary to inflammation (Hjermstad and Helwig, 1988). Tailgut cysts are discovered incidentally on routine physical examination in about 50% of cases and interestingly, some 77% occur in women (Hjermstad and Helwig, 1988). Symptoms secondary to infection are not uncomm o n and fistulous tracts to the rectum and perianal skin can develop, often following inappropriate surgery (Campbell and Wolff, 1973). Patients who present with repeated retrorectal abscesses or recurring anal fistulae, despite surgical intervention, may be harbouring a tailgut cyst. While tailgut cysts are usually benign, malignant degeneration has been reported (Marco et al_, 1982). Plain radiographs may show a soft tissue mass in the retrorectal space. Tailgut cysts are not associated with bony defects'or destruction, and soft tissue calcification is rare. Barium enema examination merely confirms the presence of an extrinsic retrorectal mass (Campbell and Wolff, 1973). Computed tomography (CT) shows a discrete well marginated retrorectal mass with CT numbers varying from water to soft tissue density. There is no sacral destruction or defect, with no evidence of invasion of continuous structures (Johnson et al., 1986). A number of cysttc lesions may arise in the retrorectal space and these investigations may provide important clues in the differential diagnosis. C h o r d o m a may be associated with bony destruction. Teratoma, chordoma, neuroblastoma, or mucinous adenocarcinoma may show calcification on plain films or CT. An anterior sacral
289
meningocoele will have an associated sacral defect. The finding of a cystic lesion without calcification or bony abnormality is not specific for a tailgut cyst, and subsequent histology m a y reveal a dermoid cyst or rectal duplication. Transrectal ultrasound has been used to assess rectal and extrarectal disease (Rifkin and Marks, 1985; Zainea et al., 1989). It is inexpensive, simple, accurate, and well tolerated by the patient. In this case report we have shown that transrectal ultrasound can provide important information on the nature of a retrorectal mass. In this case the mass was cystic, with well defined margins and no evidence of invasion, suggesting a benign lesion. Tailgut cysts should be excised completely to prevent future infection or malignant change. Simple incision and drainage is not recommended because of the risk of recurrence, infection and fistula formation.
Acknowledgements. The authors thank Dr P. M. Chennells, Consultant Radiologist, Leeds General Infirmary, for performing the transrectal ultrasound.
REFERENCES Campbell, WL & Wolff, M (1973). Retrorectal cysts of developmental origin. American Journal of Roentgenology, 117, 307 313. Caropreso, PR, Wengert, PA Jr & Milford, HE (1975). Tailgut cysts - a rare retrorectal tumor. Report of a case and review. Diseases of the Colon and Rectum, 18, 597 600. Gius, JA & Stout, AP (1938). Perianal cysts of vestigial origin. Archives of Surgery, 37, 268 287. Hjermstad, BM & Helwig, EB (1988). Tailgut cysts. Report of 53 cases. American Journal of Clinical Pathology, 89, 139 147. Johnson, AR, Ros, PR & Hjermstad, BM (1986). Tailgut cyst: diagnosis with CT and sonography. American Journal of Roentgenology, 147, 1309 1311. Marco, V, Fernandez-Layos, M, Autonell, J, Doncel, F & Farre, J (1982). Retrorectal cyst-haemartomas. Report of two cases with adenocarcinoma developing in one. American Journal of Surgical Pathology, 6, 707-714. Middeldorpf, K (1885). Zur Kenntniss der angebornen Sacralgeschwulste. Virchows Arehiv fiir Pathologische Anatomic, 101, 37 44. Rifkin, M D & Marks, G (1985). Transrectal ultrasound as an adjunct in the diagnosis of rectal and extrarectal tumors. Radiology, 157, 499 5O2. Spencer, RJ & Jackman, R (1962). Surgical management of precoccygeal cysts. Surgery, Gynecology and Obstetrics, 115, 449 452. Zainea, GG, Lee, F, McLeary, RD, Siders, DB & Thurston Thieme, E (1989). Transrectal ultrasonography in the evaluation of rectal and extrarectal disease. Surgery, Gynecology and Obstetrics, 169, 153 156.
Case Report: Tailgut Cyst-Assessment With Transrectal Ultrasound K_ A. R. H U T T O N and E_ A. B E N S O N
Department of Surgery, Leeds" General Infirmary, Leeds Tailgut cysts are derivatives of the embryonic post-anal gut. Usually asymptomatic, they are discovered in adult life as an incidental retrorectal mass. Complications include infection, with the formation of retrorectal abscesses and occasionally anal fistulae, and a long-term risk of malignant change, which means that once discovered surgical excision is advised. We present a case that was assessed pre-operatively with transrectal ultrasound. The findings were of a well defined cystic lesion, with no evidence of invasion. We believe that transrectal ultrasound is of value in assessing retrorectal lesions. Hutton, K.A.R. & Benson, E.A. (1992). Clinical
Radiology 45, 2 8 8 - 2 8 9 . C a s e R e p o r t : T a i l g u t C y s t - A s s e s s m e n t W i t h T r a n s r e c t a l U l t r a sound
T a i l g u t cysts are r a r e lesions o f d e v e l o p m e n t a l o r i g i n o c c u r r i n g in the r e t r o r e c t a l space. W e believe this is the first r e p o r t o f this u n u s u a l lesion b e i n g i m a g e d by t r a n s r e c t a l u l t r a s o u n d , a t e c h n i q u e g a i n i n g p o p u l a r i t y in the a s s e s s m e n t o f rectal a n d e x t r a r e c t a l disease.
CASE REPORT A 40-year-old woman presenting with anal fissure was found, incidentally at examination under anaesthesia, to have a retrorectal mass. Fine needle aspiration produced 5 ml of grey turbid fluid. Cytology was unremarkable. Before excisional surgery, a transrectal ultrasound was performed in the radiology department using a 5.5 MHz radial scanner (BrueI and Kjaer, Denmark). This revealed a 5 x 2 cm cystic extrarectal mass in the pre-coccygeal area. The lesion was well defined, producing deformity of the rectum without evidcnce of invzision. All layers of thc rectal wall were still visible and uninterrupted (Fig. 1). The mass was excised using a post-anal approach. She made an uneventful recovery, and was discharged on the fourth post-operative day. Exanfination of the resected specimen revealed a multicystic mass, circumscribed, which was not encapsulated. Histological examination showed the cysts to be lined with columnar epithelium, with areas of squamous metaplasia. Smooth muscle was found in the interstitial tissue, but no well developed muscle wall or neuraI plexus was seen, conforming with the pathological criteria of a tailgut cyst.
DISCUSSION T h e r e t r o r e c t a l space is a p o t e n t i a l a r e a w h o s e a n a t o m i c a l b o u n d a r i e s are the r e c t u m a n t e r i o r l y , the s a c r u m a n d c o c c y x p o s t e r i o r l y , the p e r i t o n e a l r e f l e c t i o n s u p e r i o r l y a n d the l e v a t o r ani and c o c c y g e u s m u s c l e s inferiorly. T h e iliac vessels a n d the ureters define its l a t e r a l m a r g i n s (Fig. 2). T h e first r e p o r t e d case o f a cystic m a s s in this r e g i o n was in a 1 - y e a r - o l d girl a n d p r o b a b l y r e p r e s e n t e d a rectal d u p l i c a t i o n ( M i d d e l d o r p f , 1885). S c a t t e r e d r e p o r t s since t h e n c o n f i r m t h e r a r i t y o f r e t r o r e c t a l cysts. In o n e series o f 20851 p r o c t o s c o p i e s , o n l y t h r e e s u c h m a s s e s w e r e disc o v e r e d ( S p e n c e r a n d J a c k m a n , 1962). M o s t r e t r o r e c t a l cysts p r e s e n t i n g d u r i n g a d u l t life are d e r i v a t i v e s o f the Correspondence to: Mr K. A. R. Hutton, Department of Paediatric Surgery, Clarendon Wing, Leeds General Infirmary, Belmont Grove, Leeds LS2 9NS.
Fig. 1 -Transrectal ultrasound showing the tailgut cyst (short arrows) posterior to and causing deformity of the rectal wall. The scan identifies five layers of the rectal wall of which the outer hypoechoic layer (long arrow) represents the muscularis propria.
i Retroreetal --
~ -
-
--~
Fig. 2-Anatomy of retrorectal space.
I space
TAILGUT CYST ASSESSMENT WITH TRANSRECTAL US
Hindgut \
Allantois- ~
l
ProctodeumTailgut. -.
Ii~_ Notochord - --Neural tube
=:
::.,: 5::::,,,: .........
Fig. 3 Caudal end of embryo, 4 mm stage.
embryonic tailgut (Hjermstad and Helwig, 1988). This structure is a portion of gut, distal to the future anus, present during the 3.5-8 m m stage of development when the embryo possesses a true tail (Fig. 3). Incomplete regression is said to give rise to cysts in the retrorectal space (Gius and Stout, 1938). These so-called tailgut cysts have an intestinal type of epithelial lining and no definite muscular or serosal coat (Caropreso et al., 1975). Squamous epithelium, present in 75% of cysts, may in some represent metaplasia secondary to inflammation (Hjermstad and Helwig, 1988). Tailgut cysts are discovered incidentally on routine physical examination in about 50% of cases and interestingly, some 77% occur in women (Hjermstad and Helwig, 1988). Symptoms secondary to infection are not uncomm o n and fistulous tracts to the rectum and perianal skin can develop, often following inappropriate surgery (Campbell and Wolff, 1973). Patients who present with repeated retrorectal abscesses or recurring anal fistulae, despite surgical intervention, may be harbouring a tailgut cyst. While tailgut cysts are usually benign, malignant degeneration has been reported (Marco et al_, 1982). Plain radiographs may show a soft tissue mass in the retrorectal space. Tailgut cysts are not associated with bony defects'or destruction, and soft tissue calcification is rare. Barium enema examination merely confirms the presence of an extrinsic retrorectal mass (Campbell and Wolff, 1973). Computed tomography (CT) shows a discrete well marginated retrorectal mass with CT numbers varying from water to soft tissue density. There is no sacral destruction or defect, with no evidence of invasion of continuous structures (Johnson et al., 1986). A number of cysttc lesions may arise in the retrorectal space and these investigations may provide important clues in the differential diagnosis. C h o r d o m a may be associated with bony destruction. Teratoma, chordoma, neuroblastoma, or mucinous adenocarcinoma may show calcification on plain films or CT. An anterior sacral
289
meningocoele will have an associated sacral defect. The finding of a cystic lesion without calcification or bony abnormality is not specific for a tailgut cyst, and subsequent histology m a y reveal a dermoid cyst or rectal duplication. Transrectal ultrasound has been used to assess rectal and extrarectal disease (Rifkin and Marks, 1985; Zainea et al., 1989). It is inexpensive, simple, accurate, and well tolerated by the patient. In this case report we have shown that transrectal ultrasound can provide important information on the nature of a retrorectal mass. In this case the mass was cystic, with well defined margins and no evidence of invasion, suggesting a benign lesion. Tailgut cysts should be excised completely to prevent future infection or malignant change. Simple incision and drainage is not recommended because of the risk of recurrence, infection and fistula formation.
Acknowledgements. The authors thank Dr P. M. Chennells, Consultant Radiologist, Leeds General Infirmary, for performing the transrectal ultrasound.
REFERENCES Campbell, WL & Wolff, M (1973). Retrorectal cysts of developmental origin. American Journal of Roentgenology, 117, 307 313. Caropreso, PR, Wengert, PA Jr & Milford, HE (1975). Tailgut cysts - a rare retrorectal tumor. Report of a case and review. Diseases of the Colon and Rectum, 18, 597 600. Gius, JA & Stout, AP (1938). Perianal cysts of vestigial origin. Archives of Surgery, 37, 268 287. Hjermstad, BM & Helwig, EB (1988). Tailgut cysts. Report of 53 cases. American Journal of Clinical Pathology, 89, 139 147. Johnson, AR, Ros, PR & Hjermstad, BM (1986). Tailgut cyst: diagnosis with CT and sonography. American Journal of Roentgenology, 147, 1309 1311. Marco, V, Fernandez-Layos, M, Autonell, J, Doncel, F & Farre, J (1982). Retrorectal cyst-haemartomas. Report of two cases with adenocarcinoma developing in one. American Journal of Surgical Pathology, 6, 707-714. Middeldorpf, K (1885). Zur Kenntniss der angebornen Sacralgeschwulste. Virchows Arehiv fiir Pathologische Anatomic, 101, 37 44. Rifkin, M D & Marks, G (1985). Transrectal ultrasound as an adjunct in the diagnosis of rectal and extrarectal tumors. Radiology, 157, 499 5O2. Spencer, RJ & Jackman, R (1962). Surgical management of precoccygeal cysts. Surgery, Gynecology and Obstetrics, 115, 449 452. Zainea, GG, Lee, F, McLeary, RD, Siders, DB & Thurston Thieme, E (1989). Transrectal ultrasonography in the evaluation of rectal and extrarectal disease. Surgery, Gynecology and Obstetrics, 169, 153 156.
