(Radiographics. 2001;21:575-584.)
© RSNA, 2001
Retrorectal Developmental Cysts in Adults: Clinical and Radiologic-Histopathologic Review, Differential Diagnosis, and Treatment1
Hervé Dahan, MD,
Lionel Arrivé, MD,
Dominique Wendum, MD,
Hubert Ducou le Pointe, MD,
Hocine Djouhri, MD and
Jean-Michel Tubiana, MD
1 From the Departments of Radiology (H. Dahan, L.A., H. Djouhri, J.M.T.) and Pathology (D.W.), Hôpital Saint-Antoine, 184 Rue du Faubourg Saint-Antoine, 75571 Paris Cedex 12, France; and the Department of Pediatric Radiology, Hôpital d’Enfants Armand Trousseau, Paris, France (H.D.l.P.). Presented as a scientific exhibit at the 1999 RSNA scientific assembly. Received April 13, 2000; revision requested June 1 and received July 28; accepted August 3. Address correspondence to H. Dahan (e-mail: herve.dahan@sat.ap-hop-paris.fr).
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Abstract
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Developmental cysts are the most common retrorectal cystic lesions in adults, occurring mostly in middle-aged women. They are classified as epidermoid cysts, dermoid cysts, enteric cysts (tailgut cysts and cystic rectal duplication), and neurenteric cysts according to their origin and histopathologic features. Although developmental cysts are often asymptomatic, patients may present with symptoms resulting from local mass effect (eg, constipation, rectal fullness, lower abdominal pain, dysuria), with a palpable retrorectal mass at digital rectal examination, or with a complication. Infection with fistulization, bleeding, and malignant degeneration are the major complications of developmental cysts. A well-defined, unilocular or multilocular, thin-walled cystic lesion is the main imaging feature. Uncommonly, a sacral bone defect and calcifications are associated with developmental cysts. The differential diagnosis includes cystic sacrococcygeal teratoma, anterior sacral meningocele, anal duct or gland cyst, necrotic rectal leiomyosarcoma, extraperitoneal adenomucinosis, cystic lymphangioma, pyogenic abscess, neurogenic cyst, and necrotic sacral chordoma. Complete surgical excision is indicated to establish the diagnosis and avoid complications.
Index Terms: Dermoid, 875.313 • Epidermoid, 875.369 • Pelvic organs, cysts, 875.31 • Pelvis, neoplasms, 875.31, 875.313, 875.369
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Introduction
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Retrorectal cystic lesions in adults are rare, and most cases are congenital (1). Developmental cysts are the most common congenital entity encountered in the retrorectal space (2,3) and include epidermoid cysts, dermoid cysts, and enteric cysts. There are two types of enteric cysts: tailgut cysts (so-called retrorectal cyst-hamartomas or mucin-secreting cysts) and cystic rectal duplication (4). Neurenteric cysts have also been reported (5–7).
Developmental cysts are defined by their histologic components and retrorectal location, lying anterior to the sacrum and posterior to the rectum. They occur mostly in middle-aged women and in a 3:1 female-to-male ratio. The most important complications of these cysts are infection with a secondary fistula and malignant degeneration of enteric cysts (8,9).
The differential diagnosis includes a wide variety of conditions that occur in the retrorectal space: cystic sacrococcygeal teratoma, anterior sacral meningocele, anal duct or gland cyst, necrotic rectal leiomyosarcoma, extraperitoneal adenomucinosis, cystic lymphangioma, pyogenic abscess, neurogenic cyst, and necrotic sacral chordoma.
In this article, the histopathologic appearances, clinical presentation, complications, and imaging features of developmental cysts are presented, including the findings at plain radiography, computed tomography (CT), and magnetic resonance (MR) imaging. In addition, the differential diagnosis and treatment of developmental cysts in the retrorectal space are discussed.
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Histopathologic Appearances
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Developmental cysts are epithelial cysts that appear as well-defined, thin-walled, unilocular lesions and are classified according to their origin and histopathologic features. They are thought to arise from caudal embryonic vestiges (1).
Epidermoid cysts are benign unilocular lesions filled with clear fluid. These cysts are lined with stratified squamous epithelium (Fig 1) (1,4,9). Dermoid cysts can be differentiated from epidermoid cysts with both gross and microscopic analysis because they contain skin appendages (eg, hair follicles, sweat glands, tooth buds) (Fig 2). These cysts are sometimes multiple. They are lined with stratified squamous epithelium and filled with dense muddy or fatty material (1,4,9). Enteric cysts are partially or completely lined with intestinal mucosa. They are grouped into tailgut cysts and cystic rectal duplication.
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Figure 2. Dermoid cyst. Photomicrograph (original magnification, x50; hematoxylin-eosin stain) shows mature stratified squamous epithelium lining the cyst. Note the sebaceous gland (arrowhead) and the hair follicles (arrows).
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Tailgut cysts may be multicystic. They are filled with mucoid contents and lined with a variety of epithelia, which may contain mucin-secreting or ciliated columnar cells, squamous cells, and transitional cells, often in combination (Figs 3, 4). Cystic rectal duplication is rare, representing 5% of all developmental cysts. It is defined by three histologic criteria: continuity or contiguity with the rectum, a smooth-muscle coat in two layers, and a mucosal lining, which is usually similar to rectal mucosa and sometimes contains islands of ectopic tissue (eg, gastric mucosa, pancreatic tissue, urothelial mucosa) (10–12). Neurenteric cysts differ from tailgut cysts at histopathologic analysis in that they contain a well-defined lamina propria and a more mature mucosa of endodermal origin (eg, intestinal, bladder) (5,6,13).
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Figure 3. Tailgut cyst. Photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows ciliated columnar cells lining the cyst (arrowhead). Note the normal bone tissue and bone marrow, which originate from the sacrum.
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Figure 4. Tailgut cyst with carcinomatous degeneration. Photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows the wall of the cyst, which is lined with transitional (arrow) and columnar (arrowhead) epithelium. Focal severe dysplasia with lymphatic extension is not shown.
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Clinical Presentation
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The clinical presentation is variable, depending on the size and therefore mass effect of the developmental cyst and the presence of infection in the cyst (8,10). It has been estimated that 50% of developmental cysts are asymptomatic (5), being discovered during routine physical examination or ultrasonography (US). Physical examination can demonstrate a funnel-shaped dimple in the postanal midline or a chronic fistula that may communicate with the cyst, involving the perianal skin posterior to the anus or the anal canal in the midline. Digital rectal examination may reveal a smooth, firm mass in the retrorectal space, bulging into the rectal lumen (4,8,10).
Symptoms are often related to local compression on the rectum, which causes constipation, rectal fullness, painful defecation, and lower abdominal pain, and to local compression on the lower urinary tract, which causes dysuria and urinary frequency (1,8,10,12). Dystocia and sciatic pain have been reported (14). Developmental cysts are commonly revealed by complications such as local infection with a chronic perianal fistula or rectal bleeding (1,10).
Uncommonly, the hereditary Currarino syndrome—the association of an anorectal malformation (anorectal stenosis or low-type [IA] imperforate anus), a sacral bone defect, and a presacral mass—may indicate a developmental cyst. Constipation is usually the major presenting symptom. The presacral mass may be an anterior sacral meningocele, a teratoma, an enteric cyst, a dermoid cyst, or a combination of these. Associated anomalies are frequently found in the genitourinary system (15,16).
Neurenteric cysts may be associated with neurologic symptoms (6,13).
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Complications
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The three major complications of developmental cysts that are appropriate indications for intervention are infection, bleeding, and malignant degeneration (1).
Infection
Chronic infection is the most frequent complication, occurring in 30%–50% of developmental cysts, especially in association with epidermoid and enteric cysts. The infection may manifest as pelvic pain, a local abscess, and a secondary perianal or anorectal fistula with discharge of pus. A communication or primary fistula may exist between the cyst and the anorectal lumen without infection (1,8,10,12).
Bleeding
Rectal bleeding is often observed in rectal duplications that contain ectopic gastric mucosa (1,12,17). However, rectal bleeding may be related to irritation and infection in the cyst without gastric mucosa (10).
Malignant Degeneration
Malignant degeneration has been reported in enteric cysts (9,18–20) and results in adenocarcinoma or squamous carcinoma. It has been estimated that malignant degeneration occurs in 7% of enteric cysts (21). All of the patients were older than 30 years at diagnosis (10).
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Imaging Features
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There are only limited reports of the imaging features of developmental cysts (2,5,9,18,22,23). The radiologic findings from plain radiography and barium enema examination have been described (1,18). Plain radiography uncommonly shows sacrococcygeal abnormalities such as a bone defect in association with dermoid, tailgut, and neurenteric cysts (6,8,9,15,16). A communication between the cyst and the anorectal lumen and widening of the retrorectal space on a lateral view of the pelvis may be demonstrated during a barium enema examination (Figs 5, 6). Sinography may show the sinus tract draining the cyst (Fig 6). At US, a developmental cyst appears as a unilocular or multilocular retrorectal cystic lesion, sometimes with internal echoes due to mucoid material or inflammatory debris (9,18,23).
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Figure 5a. Epidermoid cyst in a 17-year-old girl with a history of lower abdominal pain and recurrent perianal abscess and fistula. (a) Left posterior oblique image from a barium enema examination shows a smooth-walled cyst (arrows) and a communication between the cyst and the anorectal lumen (arrowheads). (b) Contrast material-enhanced axial CT scan shows the well-marginated, unilocular, hypoattenuating, air-containing cyst (arrowheads) contiguous to the rectum and vagina. Note the thick wall of the cyst, which is related to recurrent intracystic infection. (c) Coronal T1-weighted MR image shows the neck of the cyst, which communicates with the anorectal lumen (arrows). Note the low signal intensity of the cyst, which is due to its air content (rectal insufflation).
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Figure 5b. Epidermoid cyst in a 17-year-old girl with a history of lower abdominal pain and recurrent perianal abscess and fistula. (a) Left posterior oblique image from a barium enema examination shows a smooth-walled cyst (arrows) and a communication between the cyst and the anorectal lumen (arrowheads). (b) Contrast material-enhanced axial CT scan shows the well-marginated, unilocular, hypoattenuating, air-containing cyst (arrowheads) contiguous to the rectum and vagina. Note the thick wall of the cyst, which is related to recurrent intracystic infection. (c) Coronal T1-weighted MR image shows the neck of the cyst, which communicates with the anorectal lumen (arrows). Note the low signal intensity of the cyst, which is due to its air content (rectal insufflation).
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Figure 5c. Epidermoid cyst in a 17-year-old girl with a history of lower abdominal pain and recurrent perianal abscess and fistula. (a) Left posterior oblique image from a barium enema examination shows a smooth-walled cyst (arrows) and a communication between the cyst and the anorectal lumen (arrowheads). (b) Contrast material-enhanced axial CT scan shows the well-marginated, unilocular, hypoattenuating, air-containing cyst (arrowheads) contiguous to the rectum and vagina. Note the thick wall of the cyst, which is related to recurrent intracystic infection. (c) Coronal T1-weighted MR image shows the neck of the cyst, which communicates with the anorectal lumen (arrows). Note the low signal intensity of the cyst, which is due to its air content (rectal insufflation).
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Figure 6a. Cystic rectal duplication in a 15-year-old girl with a history of recurrent perianal abscess and fistula. (a) Lateral radiograph of the pelvis obtained with injection of contrast material into a perianal fistula shows a well-defined cystic lesion in the retrorectal space (arrows). Note the communication (arrowhead) with the rectum, which is anteriorly displaced. (b) Contrast-enhanced axial CT scan shows the well-defined, unilocular, thin-walled, hypoattenuating lesion in the retrorectal space (arrows) contiguous to the rectum. No sacrococcygeal abnormalities are demonstrated.
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Figure 6b. Cystic rectal duplication in a 15-year-old girl with a history of recurrent perianal abscess and fistula. (a) Lateral radiograph of the pelvis obtained with injection of contrast material into a perianal fistula shows a well-defined cystic lesion in the retrorectal space (arrows). Note the communication (arrowhead) with the rectum, which is anteriorly displaced. (b) Contrast-enhanced axial CT scan shows the well-defined, unilocular, thin-walled, hypoattenuating lesion in the retrorectal space (arrows) contiguous to the rectum. No sacrococcygeal abnormalities are demonstrated.
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CT shows a well-marginated, thin-walled, uni- or multilocular, hypoattenuating, nonenhanced lesion in the retrorectal space (Figs 6, 7). Rare cases of associated thin calcifications (Fig 7) have been reported in dermoid and tailgut cysts (21,23,24). If secondarily infected, the cyst may be thick walled with surrounding inflammatory changes (Figs 5, 8) (25). Uncommonly, the cyst may contain air due to an anorectal fistula (Figs 5, 8).
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Figure 7a. Tailgut cyst in a 65-year-old man with no symptoms. (a) Contrast-enhanced axial CT scan shows a well-defined, lobulated, homogeneous, hypoattenuating lesion (arrows) in the retrorectal space. Note the anterior displacement of the rectum (arrowheads). (b) Nonenhanced axial CT scan shows a peripheral thin calcification (arrowheads). (c) Sagittal T1-weighted MR image shows the well-defined, thin-walled cyst with intermediate signal intensity (solid arrows). It contains a small cystic component with high signal intensity (open arrow) because of a mucoid content. Note the calcification with low signal intensity (arrowheads) and absence of sacrococcygeal abnormalities. (d) Coronal T2-weighted MR image shows the well-defined cyst with homogeneous high signal intensity (arrows). Note the thin septum with low signal intensity (arrowheads).
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Figure 7b. Tailgut cyst in a 65-year-old man with no symptoms. (a) Contrast-enhanced axial CT scan shows a well-defined, lobulated, homogeneous, hypoattenuating lesion (arrows) in the retrorectal space. Note the anterior displacement of the rectum (arrowheads). (b) Nonenhanced axial CT scan shows a peripheral thin calcification (arrowheads). (c) Sagittal T1-weighted MR image shows the well-defined, thin-walled cyst with intermediate signal intensity (solid arrows). It contains a small cystic component with high signal intensity (open arrow) because of a mucoid content. Note the calcification with low signal intensity (arrowheads) and absence of sacrococcygeal abnormalities. (d) Coronal T2-weighted MR image shows the well-defined cyst with homogeneous high signal intensity (arrows). Note the thin septum with low signal intensity (arrowheads).
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Figure 7c. Tailgut cyst in a 65-year-old man with no symptoms. (a) Contrast-enhanced axial CT scan shows a well-defined, lobulated, homogeneous, hypoattenuating lesion (arrows) in the retrorectal space. Note the anterior displacement of the rectum (arrowheads). (b) Nonenhanced axial CT scan shows a peripheral thin calcification (arrowheads). (c) Sagittal T1-weighted MR image shows the well-defined, thin-walled cyst with intermediate signal intensity (solid arrows). It contains a small cystic component with high signal intensity (open arrow) because of a mucoid content. Note the calcification with low signal intensity (arrowheads) and absence of sacrococcygeal abnormalities. (d) Coronal T2-weighted MR image shows the well-defined cyst with homogeneous high signal intensity (arrows). Note the thin septum with low signal intensity (arrowheads).
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Figure 7d. Tailgut cyst in a 65-year-old man with no symptoms. (a) Contrast-enhanced axial CT scan shows a well-defined, lobulated, homogeneous, hypoattenuating lesion (arrows) in the retrorectal space. Note the anterior displacement of the rectum (arrowheads). (b) Nonenhanced axial CT scan shows a peripheral thin calcification (arrowheads). (c) Sagittal T1-weighted MR image shows the well-defined, thin-walled cyst with intermediate signal intensity (solid arrows). It contains a small cystic component with high signal intensity (open arrow) because of a mucoid content. Note the calcification with low signal intensity (arrowheads) and absence of sacrococcygeal abnormalities. (d) Coronal T2-weighted MR image shows the well-defined cyst with homogeneous high signal intensity (arrows). Note the thin septum with low signal intensity (arrowheads).
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Figure 8. Dermoid cyst in a 44-year-old woman with a history of chronic rectal fistula. Contrast-enhanced axial CT scan shows a thick-walled, unilocular cystic lesion in the retrorectal space (arrows); the cyst contains air due to a rectal fistula. Note the slightly hyperattenuating content, which may be due to skin appendages.
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MR imaging shows a well-circumscribed, thin-walled, hypointense lesion on T1-weighted images and a homogeneous, hyperintense lesion on T2-weighted images (Figs 7, 9). High signal intensity on T1-weighted images is likely secondary to mucoid (tailgut cysts) or fatty (dermoid cysts) content. Septa are more conspicuous on T2-weighted images with low signal intensity (Figs 7, 9). Focal irregular wall thickening with intermediate signal intensity on both T1- and T2-weighted images and with enhancement after contrast material injection is suggestive of malignant degeneration (9). Sacral or rectal invasion has not been described, to our knowledge. A communication between a neurenteric cyst and the subarachnoid space may be demonstrated (5,7).
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Figure 9a. Tailgut cyst with carcinomatous degeneration discovered during routine US in a 56-year-old woman. Axial T2-weighted MR images (a obtained superior to b) show a well-marginated, multilocular, hyperintense cystic lesion (arrow). Note the multiple septa with low signal intensity. The rectum is compressed and anteriorly displaced (arrowhead) without evidence of invasion.
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Figure 9b. Tailgut cyst with carcinomatous degeneration discovered during routine US in a 56-year-old woman. Axial T2-weighted MR images (a obtained superior to b) show a well-marginated, multilocular, hyperintense cystic lesion (arrow). Note the multiple septa with low signal intensity. The rectum is compressed and anteriorly displaced (arrowhead) without evidence of invasion.
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Differential Diagnosis
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Sacrococcygeal Teratoma
Sacrococcygeal teratomas are germ cell tumors containing elements derived from all three germ layers. Sacrococcygeal teratoma is the most frequently encountered presacral lesion in the pediatric age group, and most (90%) are diagnosed in the newborn period and are benign. The prevalence of malignancy increases with age; however, they are rarely discovered in adult life. They are found more frequently in females (4,26,27). Most patients (80%) have no evidence of sacrococcygeal bone abnormalities at plain radiography. At CT or MR imaging, sacrococcygeal teratomas appear as heterogeneous, well-defined lesions with mixed cystic and solid components. Uncommonly, sacrococcygeal teratomas are entirely cystic, and these are more likely to be benign. Sacrococcygeal teratomas contain fat or calcifications in 50% of cases.
Anterior Sacral Meningocele
Anterior sacral meningocele is a rare congenital disorder that usually occurs sporadically, but familial cases have been reported as part of the Currarino syndrome (15,28). It may be uncommonly associated with epidermoid cysts (2). Anterior sacral meningocele is defined as a meningeal cyst that occurs in the presacral space secondary to agenesis of a portion of the anterior sacrum. In approximately 50% of cases, associated malformations are found, such as spina bifida, spinal dysraphism, bicornuate uterus, and imperforate anus. Plain radiography shows a typical scimitar-shaped sacral bone defect in 50% of cases (Fig 10) (15,28). CT and MR imaging demonstrate the sacral defect in association with a well-defined, unilocular, fluid-filled lesion in the retrorectal space. MR imaging may demonstrate the stalk of the meningocele, which communicates with the thecal sac (Fig 10).
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Figure 10a. Anterior sacral meningocele in a 43-year-old man with a history of headache, meningitis, and chronic constipation. (a) Frontal image from a barium enema examination shows an anorectal stenosis due to extrinsic compression (arrows) with a distended proximal colon. Note the sacral bone defect (the scimitar sign) (arrowheads). (b) Frontal intravenous urogram shows bilateral hydronephrosis due to extrinsic compression of the ureters (arrows). (c) Contrast-enhanced axial CT scan shows a large, homogeneous, thin-walled, hypoattenuating mass (arrowheads) behind the rectum (solid arrow) and the bladder (open arrow), which are anteriorly displaced. Note the continuity between the mass and the sacral defect. (d) Sagittal T2-weighted MR image shows the large neck of the meningocele communicating with the thecal sac (arrow).
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Figure 10b. Anterior sacral meningocele in a 43-year-old man with a history of headache, meningitis, and chronic constipation. (a) Frontal image from a barium enema examination shows an anorectal stenosis due to extrinsic compression (arrows) with a distended proximal colon. Note the sacral bone defect (the scimitar sign) (arrowheads). (b) Frontal intravenous urogram shows bilateral hydronephrosis due to extrinsic compression of the ureters (arrows). (c) Contrast-enhanced axial CT scan shows a large, homogeneous, thin-walled, hypoattenuating mass (arrowheads) behind the rectum (solid arrow) and the bladder (open arrow), which are anteriorly displaced. Note the continuity between the mass and the sacral defect. (d) Sagittal T2-weighted MR image shows the large neck of the meningocele communicating with the thecal sac (arrow).
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Figure 10c. Anterior sacral meningocele in a 43-year-old man with a history of headache, meningitis, and chronic constipation. (a) Frontal image from a barium enema examination shows an anorectal stenosis due to extrinsic compression (arrows) with a distended proximal colon. Note the sacral bone defect (the scimitar sign) (arrowheads). (b) Frontal intravenous urogram shows bilateral hydronephrosis due to extrinsic compression of the ureters (arrows). (c) Contrast-enhanced axial CT scan shows a large, homogeneous, thin-walled, hypoattenuating mass (arrowheads) behind the rectum (solid arrow) and the bladder (open arrow), which are anteriorly displaced. Note the continuity between the mass and the sacral defect. (d) Sagittal T2-weighted MR image shows the large neck of the meningocele communicating with the thecal sac (arrow).
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Figure 10d. Anterior sacral meningocele in a 43-year-old man with a history of headache, meningitis, and chronic constipation. (a) Frontal image from a barium enema examination shows an anorectal stenosis due to extrinsic compression (arrows) with a distended proximal colon. Note the sacral bone defect (the scimitar sign) (arrowheads). (b) Frontal intravenous urogram shows bilateral hydronephrosis due to extrinsic compression of the ureters (arrows). (c) Contrast-enhanced axial CT scan shows a large, homogeneous, thin-walled, hypoattenuating mass (arrowheads) behind the rectum (solid arrow) and the bladder (open arrow), which are anteriorly displaced. Note the continuity between the mass and the sacral defect. (d) Sagittal T2-weighted MR image shows the large neck of the meningocele communicating with the thecal sac (arrow).
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Anal Duct or Gland Cyst
At histopathologic analysis, anal duct or gland cysts are mucus-secreting cysts lined with a combination of stratified squamous epithelium, columnar epithelium, and transitional epithelium. They often communicate with an anal duct or crypt. CT and MR imaging demonstrate a uni- or multilocular cystic lesion near the anal sphincter in the retrorectal space. Anal duct or gland cysts may involve the coccyx and the ischioanal space (29).
Rectal Leiomyosarcoma
Rectal leiomyosarcomas (malignant rectal stromal tumors) are rare, accounting for less than 0.1% of all malignant tumors of the rectum. Rectal leiomyosarcomas are malignant tumors of smooth muscle. Most rectal leiomyosarcomas occur in the lower third of the rectum, and they are more common in men.
The spread of these tumors is principally local and hematogenous. They may involve the rectal mucosa, leading to surface ulceration and bleeding (30). CT shows a well-circumscribed, heterogeneously enhanced, multilobulated tumor with cystic necrotic components (Fig 11).
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Figure 11a. Rectal leiomyosarcoma in a 28-year-old man with a history of rectal pain. (a) Contrast-enhanced axial CT scan shows a well-circumscribed, necrotic, hypoattenuating tumor (arrows) with enhanced solid components in the retroanal space. Note the anterior displacement of the rectal lumen (arrowheads). (b) Contrast-enhanced axial CT scan shows extension of the tumor into the retrorectal space and the pouch of Douglas.
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Figure 11b. Rectal leiomyosarcoma in a 28-year-old man with a history of rectal pain. (a) Contrast-enhanced axial CT scan shows a well-circumscribed, necrotic, hypoattenuating tumor (arrows) with enhanced solid components in the retroanal space. Note the anterior displacement of the rectal lumen (arrowheads). (b) Contrast-enhanced axial CT scan shows extension of the tumor into the retrorectal space and the pouch of Douglas.
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Miscellaneous Lesions
Subperitoneal Pelvic Adenomucinosis
Subperitoneal pelvic adenomucinosis (pseudomyxoma retroperitonei) is rare (31–33). The cysts are lined with glandular epithelium and filled with thick, gelatinous material. CT and MR imaging show well-marginated, homogeneous, septated cystic lesions (Fig 12). Uncommonly, mural nodules and calcifications are seen (32).
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Figure 12a. Subperitoneal pelvic adenomucinosis in the retrorectal space in a 50-year-old man. The lesion originated from an abandoned rectal stump above an imperforate anus and developed behind the descending colon and the colonic-anal anastomosis. (a) Sagittal T2-weighted MR image shows a large, well-circumscribed, multicystic mass (solid arrows) in the retrorectal space. Note the sites of the neo-anus (arrowheads) and the descending colon (open arrow). (b) Contrast-enhanced sagittal T1-weighted MR image shows enhanced thick septa (arrows). (c) Axial T1-weighted MR image shows the mass invading the ischiorectal fossas and the left obturator internus muscle. (d) Photomicrograph (original magnification, x100; hematoxylin-eosin stain) shows strips of simple columnar epithelium (arrowheads) with moderate cytologic atypia. Note the pools of mucin (arrow).
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Figure 12b. Subperitoneal pelvic adenomucinosis in the retrorectal space in a 50-year-old man. The lesion originated from an abandoned rectal stump above an imperforate anus and developed behind the descending colon and the colonic-anal anastomosis. (a) Sagittal T2-weighted MR image shows a large, well-circumscribed, multicystic mass (solid arrows) in the retrorectal space. Note the sites of the neo-anus (arrowheads) and the descending colon (open arrow). (b) Contrast-enhanced sagittal T1-weighted MR image shows enhanced thick septa (arrows). (c) Axial T1-weighted MR image shows the mass invading the ischiorectal fossas and the left obturator internus muscle. (d) Photomicrograph (original magnification, x100; hematoxylin-eosin stain) shows strips of simple columnar epithelium (arrowheads) with moderate cytologic atypia. Note the pools of mucin (arrow).
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Figure 12c. Subperitoneal pelvic adenomucinosis in the retrorectal space in a 50-year-old man. The lesion originated from an abandoned rectal stump above an imperforate anus and developed behind the descending colon and the colonic-anal anastomosis. (a) Sagittal T2-weighted MR image shows a large, well-circumscribed, multicystic mass (solid arrows) in the retrorectal space. Note the sites of the neo-anus (arrowheads) and the descending colon (open arrow). (b) Contrast-enhanced sagittal T1-weighted MR image shows enhanced thick septa (arrows). (c) Axial T1-weighted MR image shows the mass invading the ischiorectal fossas and the left obturator internus muscle. (d) Photomicrograph (original magnification, x100; hematoxylin-eosin stain) shows strips of simple columnar epithelium (arrowheads) with moderate cytologic atypia. Note the pools of mucin (arrow).
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Figure 12d. Subperitoneal pelvic adenomucinosis in the retrorectal space in a 50-year-old man. The lesion originated from an abandoned rectal stump above an imperforate anus and developed behind the descending colon and the colonic-anal anastomosis. (a) Sagittal T2-weighted MR image shows a large, well-circumscribed, multicystic mass (solid arrows) in the retrorectal space. Note the sites of the neo-anus (arrowheads) and the descending colon (open arrow). (b) Contrast-enhanced sagittal T1-weighted MR image shows enhanced thick septa (arrows). (c) Axial T1-weighted MR image shows the mass invading the ischiorectal fossas and the left obturator internus muscle. (d) Photomicrograph (original magnification, x100; hematoxylin-eosin stain) shows strips of simple columnar epithelium (arrowheads) with moderate cytologic atypia. Note the pools of mucin (arrow).
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Subperitoneal Pelvic Cystic Lymphangioma
Cystic lymphangioma is a rare congenital benign tumor and is more frequently encountered in the pediatric age group and in a cervical location. Occurrence in a subperitoneal pelvic location is rare. The cysts are lined with endothelium and filled with a clear fluid (chylous or serous content). Cystic lymphangioma appears as a well-defined, multicystic lesion with thin septa. Intracystic infection and bleeding are the most frequent complications (34).
Retrorectal Pyogenic Abscess
Retrorectal pyogenic abscesses often result from postoperative conditions (Fig 13). However, a chronic abscess cavity may reveal a developmental cyst (1).
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Figure 13a. Postoperative retrorectal abscess due to a colorectal anastomotic fistula in a 66-year-old man after anterior resection of the rectum for adenocarcinoma. (a) Axial T1-weighted MR image shows an irregular, thick-walled, gas-filled cavity (arrow) in the retrorectal space. Note the absence of fluid content because of complete resolution of the fistula. (b) Sagittal T1-weighted MR image shows the cavity (arrow) behind the colorectal anastomosis, which appears as a signal-void artifact due to a surgical clip (arrowheads). Note the presacral infiltration with intermediate signal intensity.
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Figure 13b. Postoperative retrorectal abscess due to a colorectal anastomotic fistula in a 66-year-old man after anterior resection of the rectum for adenocarcinoma. (a) Axial T1-weighted MR image shows an irregular, thick-walled, gas-filled cavity (arrow) in the retrorectal space. Note the absence of fluid content because of complete resolution of the fistula. (b) Sagittal T1-weighted MR image shows the cavity (arrow) behind the colorectal anastomosis, which appears as a signal-void artifact due to a surgical clip (arrowheads). Note the presacral infiltration with intermediate signal intensity.
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Sacral Cystic Lesions with Retrorectal Extension
Sacral neurilemomas are benign neurogenic lesions arising from the sheaths of the peripheral sacral nerves. CT and MR imaging show well-defined, round, heterogeneously enhanced lesions with cystic necrotic areas (27,35).
Chordoma is the most common primary sacral lesion. It is a low-grade malignant tumor that arises from notochordal remnants. Imaging shows evidence of sacral bone destruction with a heterogeneous mass that extends into soft tissue (27).
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Treatment
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The recommended treatment for developmental cysts is complete surgical excision of the epithelial lining of the cyst because of the risks of recurrence, malignant degeneration, and chronic infection (8,11,12). If malignant degeneration is suspected, total excision including the normal rectum may be necessary.
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Summary
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A wide variety of cystic lesions occur in the retrorectal space, and most are congenital. Developmental cysts are the most common lesions that represent a real radiologic-histopathologic entity, resulting in a diagnostic dilemma. Imaging may show specific signs, but the diagnosis remains histopathologic. The surgical approach is the rule to accurately establish the diagnosis and avoid complications.
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References
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Abstract
Introduction
