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 [14–16]. Malignant degeneration can occur in up to 50% of cases [17].

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.

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.

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].

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].

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.

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 [31–33]. 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].

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.

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.