Retrorectal tumors include masses of heterogeneous pathology. The cystic tumors account for approximately 40.8 % of these masses [68]. However, solid masses and inflammatory processes may develop cystic changes that further confound the diagnosis [55]. The pathology of the more common retrorectal tumors is described, including tailgut cyst, teratoma and teratocarcinoma, rectal duplication, epidermoid and dermoid cysts, anterior sacral meningocele, chordoma, and schwannoma.

A tailgut cyst is usually multiloculated. In the series from Hjermstad and Helwig [20], half of the cysts were grossly unilocular, but 81 % were microscopically multicystic. The lesion is comprised of one to two “parent cysts” and a variable number of “daughter cysts” [2]. The epithelium ranges from squamous, columnar, and ciliated columnar to transitional [2, 10]. Squamous epithelium was identified most frequently in the review from Hjermstad and Helwig. Although disorganized smooth muscle fibers may be found in the cyst wall, there is no complete muscular coat, myenteric plexus, or serosa, as in a rectal duplication [10, 20]. These lesions do not incorporate dermal appendages (unlike dermoid cysts), or intestinal epithelium (differentiating them from rectal duplications), or, for that matter, all three germ layers (contrasting them with teratomas) [61]. These thin-walled cysts contain a serous to clear, yellow, or light green mucus to a thick brown paste [2, 20, 80]. Although the cyst may closely adhere to the posterior rectal wall, there is no actual communication with the rectum unless it is created iatrogenically [20]. Inflammation (or infection), associated with approximately 50 % of the tailgut cysts in the audit from Hjermstad and Helwig, likely produces this intimate attachment. The tumor is confined to the retrorectal space but may infrequently extend superior, lateral, or anterior to the rectum [20]. Rare cases of a prerectal location for these cysts have been reported [81].

Teratomas are formed from tissue foreign to the retrorectal space [27]. These tumors are classified by their extent as intrapelvic, extrapelvic, or both. Primarily seen in the pediatric population, the tumor may grow beyond the boundaries of the pelvis (types I–III) and even extradurally to the spinal cord [10]. Grossly, teratomas may be cystic or solid. Coco and colleagues [27] described the teratoma as an encapsulated, white, globular lesion. Cystic teratomas are lined by various epithelia including squamous, cuboidal, or ciliated columnar [10]. The cystic portions enclose a keratinous or serous fluid [27]. The solid material includes the derivatives of all three germ layers, represented by endoderm (e.g., respiratory epithelium), mesoderm (e.g., cartilage and fat), and ectoderm (e.g., epidermis and skin appendages) [27]. At least two of these germ cell layers must be present for the diagnosis of teratoma [26]. These tissues may be organized to mimic diverse organs [26]. Teratomas are categorized as mature, immature, or malignant (teratocarcinoma) based on their degree of differentiation [23]. The teratoma is characteristically attached to the coccyx, leading some authors to recommend a routine coccygectomy as part of the treatment for these tumors [8, 10].

Duplications are developmental malformations that may arise at any point along the gastrointestinal tract, from the esophagus to the anus. The majority (94 %) of these duplications are hollow cystic structures, also known as enteric or enterogenous cysts [28, 29]. Tubular-shaped duplications replicate short or long segments of the intestine, often in conjunction with a urinary tract duplication or sacral abnormalities [28, 64]. Whereas most alimentary duplications (80 %) do not fistulate to the intestine, the giant diverticulum does feature such a communication [28, 31, 32]. Of the 70 cases of rectal duplications recorded in the literature by 1962, 54.3 % were tubular and 45.7 % were cystic [29, 31]. An alimentary duplication is affixed to the portion of the gastrointestinal tract with which it is associated, usually attaching to the mesenteric surface and sharing the same vascular supply [25, 29, 30]. A gastrointestinal duplication is characterized by its adherence to a section of the gastrointestinal tract; its complete (usually double layered), smooth-muscle sheath; and its mucosa composed of cells typical of the gastrointestinal tract [3, 28, 30, 32]. However, some gastrointestinal duplications contain mucosal cells not generally found in the adjacent bowel; La Quaglia and colleagues [3, 28, 30, 32, 80] identified gastric, colonic, transitional, squamous, and urothelial cells within 11 rectal duplications [28, 30, 32, 80]. A ciliated epithelium rarely has been discovered in these lesions [32]. Multiple types of epithelia may coexist in one lesion [29]. In some cases, ectopic gastric, pancreatic, or urothelial mucosa may be detected [62]. The alimentary duplication incorporates all three intestinal layers found in the normal gastrointestinal tract, namely, mucosa, muscularis propria, and serosa [30]. Rarely, one patient may have two duplications [32]. Diminutive cysts may closely accompany a duplication, predisposing a patient to a recurrence if not recognized and removed [29]. Alavanja et al. [30] described a rectal duplication in a 60-year-old woman as grossly consisting of a soft, fibrous tissue with the inner lining similar to mucosa; the microscopic examination demonstrated a urothelial-type epithelium, an inflamed submucosa, and striated muscle. A rectal duplication in a 39-year-old women treated by Monek and colleagues [32] revealed “heterotopic cylindric ciliated epithelium with mucin-secreting cells, connective tissue, and striated muscle.” In contrast to complete twinning of the hindgut, isolated rectal duplications have no association with genitourinary abnormalities [29].

Epidermoid cysts are grossly firm yet elastic, well-encapsulated lesions [82]. Ueda et al. [82] comment that epidermoid cysts exhibit a poor vascular supply. The thin-walled, unilocular epidermoid cysts are composed of a stratified squamous epithelium with keratohyaline granules [36, 62, 82]. The usually clear cyst fluid includes water, keratin, cholesterol, and desquamated epithelium [36]. In contrast, Sasaki and colleagues [56] found a “cheese-like material.” Dermoid cysts, although also lined by a stratified squamous epithelium, involve skin appendages such as hair follicles, sweat glands, and calcified materials (i.e., tooth buds) (Fig. 50.3) [4, 62]. These often multilocular lesions almost universally contain a keratinoid or sebaceous fluid, although others [27, 62, 80] noted a “muddy material.” A fatty substance is reported in 67–75 % of these lesions and calcifications are reported in 31 % [62, 80].

An anterior sacral meningocele comprises the herniation of the dural and arachnoid membranes of the spinal cord through a defect in the ventral surface of the sacrum [59]. The herniated sac is continuous with the subdural space [58]. This congenital unilocular cystic lesion is filled with clear, watery cerebrospinal fluid [59]. Chordomas, derived from the primitive notochord, are composed of a gelatinous material (Fig. 50.4) [10]. These lobulated, slow-growing tumors are locally invasive and destructive but not usually metastatic [10, 58]. The sacrococcygeal region is the most common site for a chordoma (30–50 %), although the tumors may occur at any point along the spine [6]. Schwannomas are the most prevalent neurological tumor [23]. These tumors comprise fascicular bundles of spindle cells within a capsule of epineurium [23]. Degenerative changes such as fibrosis, calcifications, hemorrhage, and cyst development often are evident [23].

The majority of retrorectal tumors are asymptomatic. Pidala et al. [48] noted that 57 % of their 14 patients reported no symptoms attributable to the tumor. An absence of symptoms was recorded by Lev-Chelouche and colleagues [41] in only 26 % of their patients. Symptoms due to these overall slow-growing lesions are vague, making the diagnosis moderately difficult. Singer et al. [61] reported an average symptom duration of 4.9 years before diagnosis, with a range of 1–11 years. Similarly, the mean length for symptoms was 3.7 years in the series from Uhlig and Johnson [2]. An acute presentation is rare [20]. Complaints generally arise related to the mass effect from the tumor, depending on its size, location, and extent [4, 9, 82]. The presence of infection, malignancy, or necrosis of the tumor usually is associated with symptoms. Pidala and colleagues [2, 48, 61, 82] found that 50 % of their patients with symptoms had an infected retrorectal cyst, which was also noted by other groups. [2, 61, 82]. Invasion of adjacent structures, especially of nerves, also produces symptoms [79]. Nerve root involvement is suggested by radicular pain, urinary or fecal incontinence (or both), or sensory or motor deficits [43]. Among the symptoms frequently identified by patients are anal, rectal, perineal, or pelvic pain or pressure; constipation, difficult or painful defecation, and narrowed or “ridged” stools [27, 30, 43, 59, 61, 83].

Pain – the most common complaint – is usually dull and difficult to localize [48, 61]. Among symptomatic patients with a tailgut cyst in the review from Hjermstad and Helwig [20], 82 % described pain in the rectum or lower back, and seven of these patients (39 %) specified that the pain was exacerbated by defecation [20]. Chordoma especially is known for causing painful defecation, although the tumor also is associated with constant rectal pain [10, 84]. In some patients, rectal pain is exacerbated by sitting, as was related by MacLeod and Purves [31] in a 39-year-old woman with a rectal duplication, who also felt a lump over her coccyx. In other patients, lower back pain may coincide with ambulation [61]. Localio and colleagues [43] recorded lower back or sacral pain in 18 patients (90 %), with a median duration of 12 months (range, 2 days to 8 years). The lower back pain attributable to a chordoma is often postural or worsened by sitting [45, 61]. In the event of invasion of the sacral plexus, nebulous pains may be experienced in the lower back or buttocks, with radiation down the legs [10, 61]. Chen et al. [36] commented that abdominal pain may result from a spontaneous rupture of a cystic lesion, as in their 62-year-old patient with a large retrorectal epidermoid tumor and constant, dull pain in the right lower quadrant.

Some patients recall trauma to the coccyx before the diagnosis of a retrorectal tumor [2]. Symptoms developed subsequent to coccygeal trauma in 15 % of patients with a malignant retrorectal tumor in the series from Cody and colleagues [44] and in 11 % with a retrorectal mass in the review from Jao et al. [45]. Sasaki and colleagues [56] suggested that trauma directly caused such lesions as an epidermoid or dermoid cyst; however, the trauma most likely brings attention to a previously asymptomatic tumor [44]. Hjermstad and Helwig [20] note that cyst rupture secondary to trauma may promote an inflammatory reaction, producing the symptoms that lead to the diagnosis of a retrorectal tumor.

Bowel symptoms are common in patients with a retrorectal tumor. Such complaints were reported by 31 % of the female patients in the series from Lee and Symmonds [46] and 44 % of the patients in the review from Wang et al. [47]. The alterations in bowel habits arise because of changes in the angulation of the rectum, impingement upon the rectal lumen, or both [58]. Fecal incontinence may result from nerve involvement [61].

Urinary symptoms are often ascribed to retrorectal tumors. Lee and Symmonds [46] attribute these urinary, as well as bowel, complaints to the size and not the pathology of the tumor. Nerve involvement of the tumor may also produce these urinary symptoms [61]. Ten percent of the patients in the series from Lee and Symmonds and 13 % in the review from Wang and colleagues [46, 47] described urinary retention, urinary incontinence, and urgency. Abnormally frequent micturation has been associated with retrorectal tumors [20, 26, 43]. Thway et al. [25] recounted one 64-year-old man with a dermoid cyst containing extramammary Paget’s disease and noted only polyuria as the main presenting feature. The patient detailed by Chen and colleagues [36] ­developed obstructive uropathy, demonstrating right hydronephrosis and hydroureter due to the retrorectal tumor. Similarly, in a case report from Yang et al. [36], a 63-year-old woman presented with acute urinary retention and suprapubic pain as a result of a 17  ×  11  ×  10 cm cystic retrorectal tumor that impinged upon the bladder, uterus, and rectum.

Painless rectal bleeding may occur secondary to a retrorectal tumor. One patient required a blood transfusion because of “massive proctorrhagia,” whereas two patients had chronic bleeding per rectumin the review from Grandjean and colleagues [20, 52]. Rectal bleeding, mucoid anal drainage, or both were experienced by four patients with developmental cysts in the series from Wang et al. [47]. Most cases of rectal duplication become symptomatic early in life. A cystic rectal duplication produces pain because of its dilatation with mucus [30, 64]. Ectopic mucosa may cause bleeding, as in a report of a 4-year-old girl with ectopic/heterotopic gastric mucosa in a giant diverticulum of the rectum, generating a rectal ulcer [28, 30]. Bleeding may also result from pressure necrosis upon the rectum from a dilated duplication [64, 78]. Bowel obstruction arising from a rectal duplication also has been encountered, although this is less common than with duplications elsewhere in the alimentary tract because of the large capacity of the rectum [3, 31]. Furthermore, in rare cases, the rectal duplication may prolapse per the rectum [3]. La Quaglia and colleagues [3] noted that infection frequently accompanies a rectal duplication. However, many of these patients initially had a suspected perianal abscess drained, thus introducing bacteria into a previously sterile mass [3]. Before surgery, a 39-year-old female patient with a cystic lesion, which later was determined to be a rectal duplication, underwent aspiration and then incision and drainage, yielding a large amount of purulent fluid; as a consequence, she developed a draining sinus tract at the incision site [31]. Rectal duplications with a fistula to the posterior midline may demonstrate drainage of a mucoid or purulent material [3].

Gynecologic complaints have been ascribed to retrorectal tumors. A 27-year-old woman reported vaginal swelling and difficult defecation in conjunction with posterior vaginal wall prolapse, thought to be consistent with a grade III rectocele, but ultimately this was determined to be a result of a retrorectal epidermoid cyst [35]. Patients may also recount irregular menstruation and dyspareunia [10, 61]. Retrorectal tumors may also complicate pregnancy. As of 1996, only 15 cases of such pregnancy complications had been recorded [40]. In the series from Lovelady and Dockerty [4], 7.8 % of the 127 retrorectal tumors were affiliated with obstetric complications. Pelvic dystocia may arise because of obstruction of the vaginal canal during delivery [4, 27]. However, small retrorectal tumors may permit vaginal delivery [59]. Uhlig and Johnson [2] described three women with a small retrorectal tumor that only became symptomatic because of an infection after a successful vaginal delivery; however, a large lesion usually mandates a Caesarean section. Krivokapic et al. [59] detailed a 37-year-old woman who underwent a Cesarean section because of an anterior sacral meningocele and enteric cyst discovered during her prenatal examinations. Yet, even a Caesarean section may be compromised by a large tumor. Sobrado and colleagues [59] chronicled a 25-year-old woman with a “huge” presacral tumor that impeded an emergency Cesarean section for hemorrhage from a placental abruption, resulting in the death of the fetus. Resection of the tumor may be attempted during pregnancy, as was done for a woman with a ganglioneuroma during her fourth month of pregnancy [2, 4]. However, at term, the increased blood flow within the pelvis renders a resection more treacherous [85].

Anterior sacral meningoceles present with headaches in one third of patients [59]. These headaches, along with nausea, may be precipitated by coughing, straining, defecation, squatting, or coitus [45, 59]. As the neck of the cyst is compressed by one of these maneuvers, the influx of cerebrospinal fluid into the meningocele is prevented, leading to a rise in intracranial pressure [59]. This elevation in intracranial pressure triggers the pain receptors within the posterior fossa, causing headache. Meningitis may arise in association with retrorectal tumors. Recurrent meningitis principally suggests a diagnosis of anterior sacral meningocele [9, 58]. A spontaneous microperforation may produce meningitis in these tumors, yielding a mortality rate of 30 % [59]. Alternatively, an iatrogenic “perforation” of an anterior sacral meningocele, as with a biopsy, may induce meningitis and is associated with a mortality rate of almost 100 % [59]. A rectothecal fistula has been reported as a source of meningitis in patients with an anterior sacral meningocele, which, in a 48-year-old man, was attributed to a stercoral perforation [86, 87]. Meningitis also has been described after the rupture of a dermoid cyst into the subarachnoid space [10].

A retrorectal tumor easily is confused with other pathologies. Singer and colleagues [61] noted that their seven patients had been treated for other complaints, including perirectal abscess; posttraumatic, psychogenic, or postpartum pain; pilonidal sinus; presacral abscess; and fistula-in-ano, before the diagnosis of a retrorectal tumor was made. These patients had an average of 4.7 diagnostic and therapeutic procedures before the correct diagnosis was made. Repeated recurrences of a perianal abscess or fistula should also suggest the rare possibility of a retrorectal tumor [9]. A 39-year-old patient, who ultimately was found to have a rectal duplication, was initially thought to have a chronic retroperitoneal abscess along with a left ureteric duplication [32]. Localio et al. [43] encountered one patient with an infected retrorectal teratoma that was instead managed as a pelvic abscess. Repeated incision and drainage procedures produce an inflammatory reaction that renders a subsequent excision of the retrorectal tumor difficult [10]. A pilonidal sinus that appears distal to the coccyx should also signal a possible retrorectal tumor [10]. Furthermore, a recurrent or nonhealing pilonidal sinus may represent an underlying retrorectal tumor. A recurrent pilonidal sinus featuring two classic midline pits in the gluteal cleft in association with a tailgut cyst was described by Satyadas and colleagues [88]. A physician may misinterpret a large, retrorectal cystic tumor as seen on transabdominal ultrasound as an ovarian cyst or other abdominal pathology, a misdiagnosis that should be suspected especially if the laparoscopy or laparotomy is negative [89–91]. Similarly, Localio et al. identified one patient with a ruptured teratoma who suffered only from recurrent fevers and malaise.

The presence of a malignant retrorectal tumor is not predicted by specific symptomatology [10]. Rarely, these masses may be discovered incidentally. In the series from Cody and colleagues [44], two asymptomatic, malignant retrorectal tumors (5 %) were diagnosed after a routine examination. The majority of patients with a malignancy are symptomatic. Jao et al. [45] comment that a symptomatic retrorectal lesion is more suggestive of malignancy than an asymptomatic mass. This finding is echoed by Glasgow and colleagues [50], who stated that benign tumors are asymptomatic more frequently than malignant masses (56 % vs. 14 %, respectively; P =  0.09). Malignancy may be heralded by symptoms such as leg paraesthesia or weakness; however, benign lesions may also give rise to these same complaints [27]. Cody et al. recorded a 95 % incidence of symptoms among their 37 patients with diverse malignant retrorectal tumors. Patients with a malignancy most frequently report pain, as was the case in 67 % of the symptomatic patients in the series from Cody et al., including sacrococcygeal, buttock, low back, rectal, or radicular pain [36, 44]. Sacrococcygeal pain (83 %) was most commonly communicated by patients with a malignant retrorectal tumor in the review from Glasgow and colleagues. They determined that only sciatic or pelvic pain was significantly associated with a malignancy (P =  0.02). Eighty-eight percent of the patients with a malignancy in the audit from Jao et al. described pain, in contrast to 39 % of the patients with a benign tumor. The series from Localio and colleagues [43] identified radicular pain (from invasion of the sacral nerve roots) in 50 % of 12 malignant tumors. These authors also correlate fecal or urinary incontinence with malignancy: their two incontinent patients were found to have advanced malignancies [9]. These bowel and bladder complaints were less commonly observed in the review from Cody et al. [44]. The interval to the diagnosis of a malignant and a benign retrorectal tumor nonsignificantly varied from 6.1 to 18.8 months, respectively (P =  0.148) in the audit by Wang et al. [47].

Retrorectal cystic lesions frequently present because of a concurrent infection. An infection may occur primarily or as a secondary process [10]. Abel and colleagues [61, 85] determined that one-third of these cystic retrorectal tumors develop an infection [61]. In the series from Spencer and Jackman [44, 57], infected tumors were found in 31.6 % of patients undergoing surgery [44, 57]. The incidence of infected developmental cysts, particularly epidermoid and enteric cysts, is reported as 30–50 % by Dahan et al. [62]. Verazin and colleagues [92] attribute this association of retrorectal tumors with a primary infection to the relatively poor vascular supply to this area, their location adjacent to the rectum, and their susceptibility to trauma or biopsy. They further comment that bacteria such as the Clostridiumspp. are common in tumors that are necrotic or advanced [92]. Patients may experience intermittent fevers and/or night sweats or pelvic pain as a consequence of the infected lesion [61, 62, 85].

A genetic basis for retrorectal tumors was first described as a syndrome in 1981 by Currarino [93]. The genetic mutation for this autosomal-dominant disorder has been localized to the homeobox gene HLXB9on chromosome 7q36 [94, 95]. In 50 % of cases, the syndrome is familial; the remainder are sporadic [93, 94]. The embryologic basis for the syndrome is uncertain. Currarino suggested the “split notochord” model in which early embryonic adhesions between the endo- and ectoderm lead to the characteristic findings of this syndrome [93, 94, 96]. This autosomal-dominant genetic disorder includes retrorectal tumors, anorectal defects (anorectal stenosis or a low imperforate anus), and anterior sacral abnormalities [62]. A myriad of retrorectal tumors may be involved in this syndrome, including anterior sacral meningocele, enteric cyst, tailgut cyst, dermoid cyst, or teratoma [25, 62]. The most common retrorectal masses in this syndrome are the anterior sacral meningocele and teratoma [96]. More than one retrorectal tumor may coexist [62]. Malignant degeneration of the retrorectal mass was identified in three children, all 2 years old, and four adults and included five teratomas, one leiomyosarcoma, and one neuroendocrine tumor [94]. The classic triad of retrorectal tumor, complete or partial sacral agenesis, and anorectal anomalies does not frequently occur concurrently [93]. By 1984, only 40 cases of a complete triad had been recorded [93]. In 80 % of cases, a complete Currarino triad is diagnosed by the age of 10 years; those patients with an incomplete Currarino syndrome are usually detected as adults [96]. The sacral defect is a constant finding [97]. Among the other abnormalities possibly evident in this syndrome are those of the kidneys, urinary tract, and gynecologic organs [25, 62]. A tethered spinal cord was found in 17 patients (58.6 %) in the review from Crétolle et al. [94]. Constipation is the most common complaint among these patients [62]; however, patients are asymptomatic in 33 % of cases [24, 94, 98]. Patients may present acutely with a bowel obstruction, perianal sepsis, or meningitis [95]. Family members should be screened for the syndrome with a sacral radiograph and genetic counseling should be offered [93].

The correct diagnosis of a retrorectal tumor begins with the clinical suspicion that such a lesion is present. The identification of these masses initially relies upon the physical findings of an examination. The primary radiographic means to diagnose these lesions include endorectal ultrasound (ERUS), computerized tomography (CT), and magnetic resonance imaging (MRI). Among the other diagnostic modalities available are endoscopy, barium enema, angiography, and myelography, when appropriate.

A postanal dimple represents a connection between a retrorectal cystic lesion and the perianal skin. However, a clear tract between the postanal dimple and the cyst is only variably present [2]. The cone-shaped external opening occurs in the posterior midline, primarily over the perianal skin but possibly in the distal anal canal [3, 4]. The postanal dimple is distinguished from a fistula-in-ano by the absence of an internal opening at the dentate line [23]. However, a postanal dimple may coincide with a fistula-in-ano, as noted by Grandjean and colleagues [52], who treated two patients with a retrorectal tumor associated with both a postanal dimple and an intrasphincteric fistula-in-ano. Twenty percent of cystic rectal duplications demonstrate a postanal dimple [29]. In a series of 11 pediatric patients, La Quaglia et al. [52] identified such dimples in five children (45 %). These postanal dimples also are affiliated with 2–34 % of congenital lesions such as tailgut cysts and epidermoid cysts [1, 48, 61]. A postanal dimple was detected in 34.6 % of patients with a retrorectal cyst in the series from Uhlig and Johnson [2, 50] but in 5.8 % of retrorectal tumors in the review from Glasgow and colleagues [50]. Singer et al. [2, 50] detailed a well-epithelialized external opening that led to a retrorectal cystic lesion, a tailgut cyst, with persistent serosanginous or purulent drainage in an 18-year-old woman. The origin of the postanal dimple is uncertain. Hjermstad and Helwig [20] suggest that the dimple arises from traction on the postanal skin by the filum terminale during fetal development.

An external mass is encountered infrequently in adult patients. Primarily, extrapelvic extension of these masses, usually teratomas, is exhibited by neonates [6, 9]. Coco and colleagues [27] described a 40-year-old woman, with a history of a pelvic mass since birth, who presented with pelvic pain and a tender lesion on her right buttock, which later was determined to be a teratoma. The same authors also reported a 50-year-old man, diagnosed with a pelvic mass 25 years before presentation, with a palpable tumor on his right buttock, a dermoid cyst. A mass on the left buttock similarly was discovered in a 39-year-old woman with a rectal duplication [32]. Coccygeal abnormalities may be revealed during physical examination. Uhlig and Johnson [2] recorded six patients (9.5 %) with a deformed coccyx in addition to a retrorectal tumor.

The majority of retrorectal lesions are identified during digital rectal examination. Such evaluations often are performed in asymptomatic patients during routine physical examinations or prenatal assessments [80]. Jao et al. [45] diagnosed these tumors via a digital examination in 97 % of their patients. In contrast, only 35 % of the retrorectal tumors were palpated during digital examination in the audit from Glasgow and colleagues [50]. The index finger may distinguish a fixed mass or presacral fullness, usually in the midline but occasionally to its right or left [10]. In the series from Bellotti et al. [99], three retrorectal tumors were located in the posterolateral position. Because many of these tumors, particularly the cystic lesions, are soft and compressible, their presence may be overlooked. Various authors [2, 27, 61] emphasize that the examining digit must be maneuvered to feel the entirety of the retrorectal space. An epidermoid cyst is [68, 82] described as a firm, elastic, nontender mass during digital examination. An anterior sacral meningocele is suggested by a soft, fluctuant mass [59]. When the patient completes a Valsalva maneuver, an anterior sacral meningocele may enlarge (the “cry impulse”) during the digital examination [45]. Fullness and fixation in the retrorectal space implies an infected cyst [10]. Displacement of the rectum or anus or narrowing of the lumen as a result of the tumor may be evident [30, 65]. Sacral nerve invasion may be indicated by a patulous anus or hypoesthesia of the perineum [61]. A fistula may be discovered during the examination: a rectal fistula was detected during a digital rectal examination in four patients with a retrorectal tumor in the series from Mathis et al. [54]. A malignant lesion is not necessarily distinguished from a benign tumor by the digital rectal examination. Localio and colleagues [43] found that primary sacral malignancies were characterized by their fixation, yet this also was true of five benign tumors. Yang et al. [37] noted a “rubbery” retrorectal tumor that later was determined during digital examination to be an epidermoid cyst containing a squamous cell carcinoma. Chordomas were assessed to be primarily smooth, nontender, and rubbery [10, 43, 45], although two of the eight tumors in the review from Localio and colleagues were lobulated. In contrast, Lev-Chelouche et al. [41] commented that their patients’ chordomas were solid and fixed to the sacrum. Invasion of the sacrum may manifest with sacral tenderness during transrectal palpation [41].

Specific tumor markers may be elevated in some cases of retrorectal tumor. Coco and colleagues [27] identified a patient with a teratoma with a cancer antigen (CA) 125 of 109 ng/mL, although the levels of CA 15-3, CA 19-9, α-fetoprotein, and β–human chorionic gonadotropin were within normal limits. Teratomas feature a high carcinoembryonic antigen and α-fetoprotein level in 82 and 53 % of cases, respectively [45]. Chêne and Voitellier [24] commented that an isolated increase in the level of carcinoembryonic antigen (CEA) may indicate an epidermoid cyst. An elevated CA-125 of 103.4 U/mL (normal, <35 U/mL) was demonstrated in a 62-year-old woman with a epidermoid cyst that initially was thought to be an ovarian cancer [36]. An elevated level of CA 19-9 has been reported in association with a retrorectal tailgut cyst, but the level decreased to the normal range 1 month after resection [100]. A high tumor marker level only variably predicts a malignancy. In a 54-year-old woman described by Rogers et al. [71], malignancy in a recurrent, previously benign tailgut cyst was signaled by an elevated CEA level. An elevated serum α-fetoprotein also is associated with a teratocarcinoma [24, 45]. These tumor markers have an uncertain value for the postoperative surveillance of tumor recurrence. The recurrence of a tailgut cyst containing a poorly differentiated adenocarcinoma after surgery and radiation therapy was heralded by a rise in the levels of CEA and CA 19-9, both of which had been markedly elevated before treatment but then had normalized [101].

Flexible endoscopy or a rigid proctoscopy should be performed to rule out mucosal involvement of the rectum. These examinations generally reveal normal mucosa, possibly with a smooth indentation of the posterior rectal wall [68]. Palanivelu and colleagues [65] identified extrinsic ­compression during a flexible sigmoidoscopy in their patient with a large epidermoid cyst. A “bulging mass” was noted by Alavanja et al. [30] during a colonoscopy to work up a retrorectal lesion, ultimately determined to be a rectal duplication. Punctate mucosal erythema in association with a posterior fullness due to a retrorectal tumor was described by Abel and colleagues [85]. In the 20 % of duplications that communicate with the rectum, the connection may be demonstrated by endoscopy. Rarely, invasion of the rectum by the retrorectal tumor may be evident [1]. Glasgow et al. [50] found that proctoscopy alone was associated with a 52 % sensitivity for the diagnosis of a retrorectal tumor.

A plain radiograph of the pelvis is of limited value in the assessment of retrorectal tumors. Eighty-five percent of the plain abdominal roentograms were normal in the series from Grandjean and colleagues [52]. Wolpert et al. [9] suggest that positive findings, even sacral abnormalities, often are obscured by the superimposed bowel gas and surrounding soft tissue. The films may exhibit destruction or displacement of the sacrum or coccyx, a soft-tissue mass, or calcifications [9, 61]. An anterior sacral meningocele is affiliated with a pathognomic scimitar sign (a rounded, concave sacrum),absence of the coccyx, or both in 50 % of cases; this finding relates to abnormal bone development due to the mass effect from the tumor [59, 62]. Similar sacral anomalies are rarely seen with tailgut cysts. Hjermstad and Helwig [10, 20] encountered spina bifida occulta (n =  4), a healed coccyx fracture (n =  1), an anteflexed coccyx (n =  1), and an absent coccyx with a sacral bone deformity (n =  1) among their patients with a tailgut cyst; they commented that the sacrococcygeal abnormalities may arise from the same defect that produced the persistence of the postanal gut (i.e., tailgut cyst) [10]. Calcifications are primarily found in mature teratomas, although dermoid cysts may also demonstrate calcifications from tooth buds [27]. A calcification in a tailgut cyst may indicate a concurrent malignancy [20]. Sacral bone destruction is most reliably linked with malignancy [9, 45]. Localio and colleagues [43] noted that sacral bone destruction was displayed by 11 patients (92 %) with a malignant tumor, particularly in all eight cases of chordoma, but by none of the patients with a benign mass. Seventy-nine percent of the tumors with sacral bone destruction were malignant in the experience of Jao et al. [45

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