Retrorectal Cyst



Fig. 14.1
Borders of the retrorectal space



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Fig. 14.2
Anatomy of the pelvis with surrounding structures, mesentery removed




Differential Diagnosis and Classification


Lesions found in the retrorectal space can be broadly categorized as congenital or acquired, and benign or malignant [6]. Previously, classification systems have used these categories to give four distinct groups with similar clinical presentation, diagnosis, treatment, and prognosis, despite the variety of histologic subtypes still within each category [6]. Other classifications previously divided tumors into congenital, neurogenic, osseous, and miscellaneous [7]. Table 14.1 demonstrates the breadth of tumors that can be found in the presacral region, categorized by a combination of the above two classification systems.


Table 14.1
Classification of retrorectal tumors














































































 
Benign

Malignant

Congenital

Epidermoid cyst

Chordoma

Dermoid cyst

Teratocarcinoma

Anterior sacral meningocele
 

Enterogenous cysts
 

Tailgut cysts (cystic hamartomas)
 

Teratomas
 

Neurogenic

Ganglioneuroma

Ependymoma

Neurofibroma

Neuroblastoma

Neurolemmoma

Neurofibrosarcoma

Schwannoma

Ganglioneuroblastoma

Osseous

Bone cysts

Osteogenic Sarcoma

Chondroma

Ewing’s Sarcoma

Osteochondroma

Chondromyxosarcoma

Osteoma

Myeloma

Giant cell tumor

Chondrosarcoma

Miscellaneous

(Includes Inflammatory)

Foreign body granuloma

Desmoid tumor (locally aggressive)

Abscess/fistula

Lymphoma

Angiomyxoma

Angiosarcoma

Leiomyoma

Soft tissue sarcoma

Hemangioma

Carcinoid
 
Metastatic disease


Source Modified from Uhlig and Johnson [7], Lev-Chelouche et al. [6], and Szmulowicz and Hull [8]


Developmental Cysts


The majority of retrorectal or presacral tumors is congenital cystic lesions, also referred to as developmental cysts, and originate from developmental abnormalities such as the persistence of embryologic remnants, embryologic sequestration, or failure of midline fusion [9]. These include epidermoid cysts, dermoid cysts, enterogenous cysts, tailgut cysts, and teratomas and can make up 55–81% of retrorectal tumors [2].

Epidermoid and dermoid cysts are both noted to form due to failure of fusion or defect of the ectoderm, with the difference being skin appendages within epidermoid cysts, while dermoids contain only squamous cells [5, 10]. They are both generally benign, well-circumscribed lesions that can communicate with the skin and may be associated with a post anal dimple. Abel reported up to 1/3 of all cysts will become infected [11]. This complicates diagnosis, and they may be confused for perirectal abscesses and patients have been found to undergo multiple prior procedures before the correct diagnosis is made [10, 12].

Enterogenous cysts are endodermal in origin. They often present as multilobular cysts with a variety of epithelial contents. While predominantly benign, malignant degeneration has been reported within rectal duplications [13]. Tailgut cysts, or cystic hamartomas, are also multicystic and contain a range of epithelial contents.

Teratomas are derived from totipotential cells and include all three germ cell layers. They can be categorized as immature, mature, or malignant (teratocarcinoma) depending on the degree of differentiation of their contents. Teratomas are more common in the pediatric population with adult incidence ranging from 1 in 30,000–43,000 live births [1416]. Malignant degeneration can occur in up to 50% of cases [17].


Malignant Tumors


Malignant retrorectal tumors have been reported to account for 8.7–50% of cases [7, 18, 19]. Some series demonstrate a male predilection for malignant tumors with up to 86% being found in men [20], while other series report no difference in malignancy by sex [7, 12]. Cystic masses are less frequently found to be malignant (10%), while solid tumors are malignant in up to 60% of cases [12]. Chordomas are the most commonly reports malignant retrorectal tumors, and develop from a persistent mesodermic notochord.


Other Entities


Anterior sacral meningoceles can also be found in this presacral space. These congenital cystic lesions are made up of herniated dural and arachnoid membranes of the spinal cord through a defect in the sacrum. These may be associated with other congenital anomalies. Care must be taken not to enter these tumors and contaminate the cerebral spinal fluid for risk of meningitis given their direct connection to the subdural space.

Neurogenic and osseous tumors are also located in the retrorectal space along with a variety of miscellaneous entities including inflammatory conditions and metastatic disease from other sites (Table 14.1). Osseous tumors can often be differentiated on imaging due to their association with sacral destruction.


Diagnosis and Preoperative Management


Presacral tumors often present very indolently with nonspecific symptoms that make them difficult to diagnose. Many are found incidentally during pelvic or gynecologic examinations. Benign lesions have been reported to be more common in females, though women of childbearing age often undergo pelvic and rectal exams more often than their male counterparts, therefore this selection bias may partly explain this difference. Malignant lesions tend to have an equal distribution among the sexes [7, 12].

The most common symptom reported by patients is pain, which is vague, difficult to localize, and longstanding. Pain has been reported to be associated more frequently with malignant tumors than benign (88% vs. 39%) [2]. Other symptoms reported in the literature include perineal discharge, constipation, incontinence of urine or stool, sexual dysfunction, limb weakness, perineal pressure, or rectal bleeding [2123]. These vague symptoms and presentations can often lead to misdiagnoses including perianal abscess, fistula in ano posttraumatic pain, pilonidal cyst, presacral abscess, postpartum pain, and psychogenic pain [12]. Average symptom duration is reported at up to 4.9 years in patients with misdiagnoses, and patients undergo an average of 4.7 invasive procedures in order to diagnose or treat their disease [12].

A thorough history and physical exam with careful attention to the sacral nerves, presence of a post anal dimple, or fullness in the precoccygeal area should be performed. Digital rectal exam should also be performed and these lesions are palpable on DRE in anywhere from 35 to 97% of patients [2, 20]. Sigmoidoscopy can also be performed to determine invasion of the rectal wall. A high index of suspicion is necessary in patients with multiple prior incision and drainage procedures and recurrent infections or any of the above physical exam findings.

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Fig. 14.3
CT imaging of cystic hamartoma. Axil view, sagittal view

Imaging has improved diagnosis and management of this wide array of disorders in recent years. CT scan and MRI are most often used, and both are reported to have 100% sensitivity for diagnosing the presence of a retrorectal mass [20] (Fig. 14.3). Imaging determines whether a lesion is cystic or solid, the relationship to surrounding structures, and the boundaries of the tumor. While imaging modalities can be helpful for planning operative approach, they often are not sufficient for diagnosis. Correct diagnosis is made by CT alone in only 15% of one reported cohort, and 67% via MRI [24] (Fig. 14.4). Of these patients, 49% could not be given a diagnosis based on imaging alone, and 35% of those cases had malignancy on final pathology [24]. Transrectal ultrasound has also been used in combination with rigid proctoscopy with a reported sensitivity of 100% visualization of retrorectal tumors for this combined modality [12, 20].


Preoperative Biopsy


The role of preoperative biopsy of retrorectal tumors has been controversial in the literature. Older literature reports significant risks including seeding the biopsy tract causing increased recurrence rates, increased risks of infection, and risk of injury to surrounding structures including but not limited to the anococcygeal ligament, presacral nerves and sympathetic ganglion, bowel, bladder, vasculature, uterus, and adnexae [25]. With the increased use of high resolution CT guided biopsy these risks have become minimized. Studies have shown minimal complications. One such study reported 76 biopsies performed on 73 patients with only two complications (both hematomas with no clinical sequelae) [24]. These biopsies were 96% sensitive, 100% specific, and had 91% final pathology correlation, overturning diagnoses in 29% of their patients who had been given definitive diagnoses based on imaging alone [24]. Additionally, in 39 biopsies of malignant tumors in another series, there were no complications [23].

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Fig. 14.4
MRI of retrorectal tailgut cyst; T2 weighted axial view, T2 fat sat sagittal view

Moreover, the importance of obtaining a tissue diagnosis prior to surgical excision lies in the potential to change treatment, as some solid tumors may be better managed with preoperative radiation, chemotherapy or both. Shrinking a large pelvic tumor can alleviate potential operative complications by decreasing the surgical burden. Messick et al. biopsied 32% of their patients preoperatively, with no reported complications, and five patients had a management change as a result of the biopsy [4]. They also reported no change in local recurrence rates (21% benign, 41% malignant in their series) when compared with prior case series, despite the increased use of preoperative biopsy. Other authors advocate that biopsy should be reserved for tumors that appear unresectable to aid in planning for adjuvant therapy [20].

There is little to no role of biopsy in a purely cystic lesion, as many of these are benign, and even with malignant transformation, the treatment approach does not change. There is, however, an increased risk of infection with transrectal and transvaginal biopsy, and thus these routes should also be avoided [10]. Finally, if biopsied, it should be done so the tract can be excised with the tumor if it is malignant; therefore, biopsy approach should be incorporated into the operative plan [10].


Surgical Management


All retrorectal tumors should be surgically excised, with the exception of presumed malignancies such as Ewing’s sarcomas, desmoid tumors, osteogenic sarcomas, or neurofibrosarcomas, which benefit from preoperative radiation or chemotherapy [26]. All other tumors should be removed because even with presumed benign lesions, malignant transformation can occur, despite imaging and even biopsy [2]. Additionally, about 1/3 of cystic lesions will become infected over time, thus making eventual operative resection more difficult and fraught with complication as tissue planes become inflamed [11], and once infected up to 30% recurrence rate is reported in such cases [2]. Moreover, anterior meingoceles are at risk for life threatening meningitis if infected. Additionally all woman of childbearing age should have retrorectal masses excised due to their potential to obstruct the vaginal canal and cause dystocia during childbirth [7, 27, 28].


Surgical Approach


Preoperative planning taking into consideration the extent of the tumor, involvement of adjacent structures, and the relationship to the sacrum is important in deciding how to proceed. Most authors also advocate preoperative bowel preparation to reduce infectious complications in the event that the rectum is entered inadvertently. The operative approach varies depending on the relationship of the tumor to the sacrum.

Low-lying tumors, such as those in which the superior most aspect can be palpated on digital rectal exam, should be approached by a posterior, or perineal approach [19] (Fig. 14.5). This approach is also useful for infected cysts, though some advocate draining infected cysts via CT guidance prior to operative resection, and proceeding with definitive resection once the acute inflammation has resolved [29]. A paracoccygeal incision is made, and the coccyx may be removed. Of note, vascular control is difficult via this approach, and if the tumor extends superiorly and proximal control cannot be obtained, it may be necessary to convert to laparotomy to control bleeding.

If the tumor extends above S-3, a combined abdominosacral approach is advocated. This method primarily allows for control of the iliac vessels, and anterior mobilization of the ureters and rectum from the tumor, while also allowing the tumor to be dissected from the sacrum and the tenuous blood supply posteriorly.

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Fig. 14.5
Visualization of tailgut cyst intraoperatively via posterior “Kratske” approach, arrow identifies cyst

If the entirety of the tumor lies at or above S-4 [12] the abdominal approach is preferred, though some authors report S-3 to be their cutoff [9]. More recently, there have been case reports describing laparoscopic approach to these tumors, citing the excellent visualization of the deep pelvic anatomy [30].

Finally, a transanal approach is rarely used to resect these lesions. There are reported excisions of tailgut cysts or cystic hamartomas in this fashion with no complications or recurrence [3133]. One group used this approach for 11 patients, with only one developing a complication of a presacral abscess [3]. Though other authors prefer that this method only be used for lesions that had previously been drained through the rectum, as well as small epidermoid and dermoid cysts, noting poor visualization as a barrier to complete resection [5].


Complications



Preoperative Complications


As demonstrated thus far, this heterogeneous group of tumors faces many complications even prior to diagnosis. Preoperatively patients face the risk of delayed and missed diagnosis, infection, recurrent procedures, and malignant degeneration of previously benign lesions. Biopsy continues to be debated, with the risks of bleeding, injury to surrounding structures, and possible spread of malignant or infected tissues.


Intraoperative and Postoperative Complications


Complication rates for the operative intervention vary in the reported literature. The most devastating intraoperative and postoperative complications include bleeding, infection, rectal perforation, and incomplete excision/recurrence. Other frequently reported complications include bowel and bladder dysfunction (incontinence, retention), sexual dysfunction, ureteral injury, pelvic floor dysfunction, neurologic symptoms, and low incidence of various other common surgical complications, such as DVT, pneumonia, and bowel obstruction (Table 14.2). Table 14.2 shows reported complication data and interpreted blood loss from many of the larger case series discussing retrorectal tumor excisions.


Table 14.2
Complications during and after surgery for various retrorectal tumors























































 
Cases

Mortality

Morbidity

Bleed

Infection

Rectal injury

Bowel or

bladder

Sexual

Neurologic

Other

Localio et al. [22]

20

1 (5%)

(sepsis)

12 (60%)

4 (20%)

4 (>1500 mL)

1 (5%)

urosepsis wound, death

0

6 (30%)

5 UR

1 UI

0

2 (10%)

2 LE weakness

0

Cody et al. [23]

27

1 (3.7%)

(bleed MI)

8 (30%)

4 (15%)

1 MI/death

1 re-op

2 hematoma

0

0

3 (11 N%)

3 UR

0

1 (3.7%)

1 foot drop

1 (3.7%)

1 SBO

Jao et al. [2]

102

0

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Oct 18, 2017 | Posted by in GASTROENTEROLOGY | Comments Off on Retrorectal Cyst
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