Keywords

1 Tailgut Cysts and Rectal GIST: An Overview

1.1 Anatomic Considerations

Tailgut cysts (TGC) and rectal gastrointestinal stromal tumors (GIST) are rare tumors found in the retrorectal space, which is bounded anteriorly by the rectum and mesorectal fascia, posteriorly by the presacral fascia, superiorly by the peritoneal reflection, inferiorly by the rectosacral and Waldeyer’s fascia, and laterally by the lateral ligaments, iliac vessels and ureters [1].

1.2 Tailgut Cysts

TGC predominantly affect female patients in the third to the sixth decade of life, although malignancy is most common in males. They are asymptomatic in 50% of cases; in the other half of patients, they may present with mass effect-related urinary and intestinal symptoms, such as constipation and rectal tenesmus. Other symptoms include vague, long-standing pain in the sacrococcygeal or perineal area. Lower limb neurologic symptoms have also been described in the literature. Most TGC are benign; malignant lesions tend to be symptomatic and are not detected until later in their development. Complications include cyst infection, defecation disorders, or dystocia.

1.3 Rectal Gastrointestinal Stromal Tumors

GIST are rare tumors arising from Cajal cells. Rectal GIST account for 5% of all GIST [2]. The incidence of GIST is higher in the fifth to sixth decade of life. Symptoms may be nonspecific as with TGC, with pelvic or anal pain, gastrointestinal bleeding, anemia or weight loss, or be absent. Contrast-enhanced computed tomography (CT) is the imaging modality of choice for the diagnosis of GIST. Fluorodeoxyglucose-positron emission tomography (FDG-PET) has good specificity and sensitivity for assessing tumor response after imatinib mesylate treatment. Approximately only 30% of GIST are malignant. Rectal GIST are classified by the National Institutes of Health (NIH) as “very low”, “low”, “intermediate”, or “high” risk tumors, depending on location, mitotic index and size [3]. Diagnosis of a rectal GIST has been associated with a poor overall prognosis. One reason for the poor prognosis of rectal GIST is that the rate of tumor rupture is more than four times that of non-rectal GIST, and perforation is associated with a high-risk prognosis [4]. Radical resection with en-bloc excision of the mass is the standard first-line treatment for all localized GIST. Local excision, low anterior resection, abdominoperineal excision of the rectum (APER), and pelvic exenteration might be needed. The primary goal of surgery is to obtain negative microscopic margins without causing bleeding or rupture of the pseudocapsule [5]. Transanal resection is one of the most minimally invasive methods but is limited by the distance from the dentate line [6]. Transcoccygeal excision is adequate for lower rectal GIST but has high postoperative morbidity, with fistulae occurring in 21% of patients [7]. For small rectal GIST, local resection may be safe [8]. Treatment of advanced rectal GIST requires a multimodal therapy with imatinib mesylate and is indicated for first-line treatment of metastatic or unresectable GIST.

2 Advantages of Robotic Surgery Compared with Open and Laparoscopic Approaches

Traditional approaches include laparotomy, perineal excision or a combination of both. Although most retrorectal lesions can be safely removed with a posterior and transperineal approach, particular challenges may arise when the lesion is large, extends deep into the pelvis, and may be fused to surrounding pelvic structures; in these cases, traditional extraperitoneal approaches may not be safe or appropriate [9, 10]. Laparoscopic surgery has been shown to be safe, effective, and advantageous in resecting rectal GIST, including anus-preserving surgery, due to the minimally invasive approach [11]. Robotic technology allows for better visualization, making it easier to remove the tumor from the pelvic viscera and extend it to the pelvic floor [12].

3 Preoperative Considerations, Patient Positioning, and Port Placement for the Robotic Approach

3.1 Preoperative Considerations

For rectal GIST resections, there is no standard approach: an individualized approach is required, ranging from transanal excision, transanal minimally invasive (TAMIS) excision, transcoccygeal excision, rectal resection, or APER and pelvic exenteration in locally advanced cases. For TGC, transabdominal, transperineal, parasacral, or mixed approaches have been described. The decision on the ideal approach depends largely on the anatomical relationship of the tumor to the S3 sacral level [13]. Tumors above S3 require an anterior transabdominal approach, whereas tumors below S3 may benefit from a posterior parasacral approach or a combined anteroposterior approach [14]. However, patients with tumors below S4 can be approached with a robotic-assisted anterior approach above the elevator muscles plane, with good results and low postoperative morbidity. Preoperative planning is crucial and based on CT, magnetic resonance imaging (MRI) and 3D-based imaging [15]. Artificial intelligence-based reconstructions and 3D printing could also be used [16,17,18]. Such technologies can potentially be integrated into the robotic platforms,

3.2 Patient Positioning

Depending on the type of procedure required, different preoperative preparations could be considered [19, 20]. After general anesthesia, the patient is positioned supine in a modified Lloyd-Davies position.

3.3 Port Placement

An in-depth description of port placement and suggested steps for the robotic excision of TGC has been previously reported [21]. Robotic ports are placed in the position used for pelvic dissection. A curved line is drawn between the umbilicus and the two iliac spines to delineate the line where the trocars are to be placed (Fig. 23.1a). Pneumoperitoneum is formed with a Veress needle at the Palmer point.

Fig. 23.1
Three intra-operative photographs of the abdomen part. A curved line is drawn in the navel. The ports are placed through the curved line. The ports are inserted into the fat layer.

(a) Curved line for port placement. (b) Ports in place. (c) Robotic instruments used

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Four robotic 8-mm trocars are placed along the drawn curved line, at a distance of 6–8 cm (Fig. 23.1b), depending on BMI. An 8-mm port utilized as the assistant port is placed 5 cm cranially and laterally from the intersection of the trocar line and the right midclavicular line.

4 Surgical Technique in Steps

The patient is placed in a Trendelenburg position and tilted on the right side. The small intestine and the greater omentum are manually displaced toward the upper abdomen. Adhesiolysis is performed if needed.

4.1 Docking

The robotic cart comes from the left side of the patient at a 90° angle. The robotic arms are aligned with the trocars prior to docking. Camera targeting toward the pelvis is performed. The robotic arm distribution is: R1, fenestrated tip-up forceps; R2, bipolar forceps; R3, camera; R4, monopolar curved scissors or needle holder (Fig. 23.1c).

4.2 Lateral Mobilization of the Rectum

With the tip-up forceps in R1, the sigmoid colon is retracted cranially and laterally to expose the sacral promontory (Fig. 23.2a). Further countertraction can be provided with a laparoscopic grasper from the assistant port. Dissection begins anterior to the sacral promontory and continues to the right border of the mesorectum or pararectal groove (Fig. 23.2b). Care must be taken to clearly identify and protect the left common iliac vein, median sacral vessels, right hypogastric nerve, and both ureters. The tip-up grasper is repositioned continuously to allow for adequate traction (Fig. 23.2c–d). Careful dissection is performed in the mesorectal plane, allowing right-sided mobilization of the rectum down to the pelvic floor and adequate exposure of the perineal body.

Fig. 23.2
6 close-up intra-operative photographs of layers of fat in the colon areas. The muscles are held upward by an instrument. A bulk of muscles is removed from pelvic area.

(a) Sigmoid colon retraction. (b) Dissection anterior to the sacral promontory. (c–d) Tip-up grasper used for rectal retraction. (e) The tumor is dissected from the pelvic floor. (f) Extraction using a laparoscopic bag device

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4.3 Dissection from the Pelvis

The tumor must be carefully separated from the posterior rectum to avoid damage to or perforation of the rectum but also of the tumor itself (Fig. 23.2e). After the tumor is fully mobilized, the surgical bed is washed out and hemostasis is confirmed. At this point, an air leak test can be performed to ensure no injury has been caused to the rectum. The specimen is extracted using a laparoscopic bag device either through the port or a small Pfannenstiel incision, depending on the size of the specimen (Fig. 23.2f). The trocars are removed under direct vision.

5 Postoperative Course, Follow-Up, and Outcomes

Intraoperative complications include hemorrhage from the presacral venous plexuses, rectal injury, sacral plexus nerve injury, or urethral injury [22]. Early postoperative complications include bleeding, wound infection, rectal and urethral injury, temporary sensory loss, and formation of a presacral abscess. Long-term complications may occur (low back pain, numbness, and neuropathic lower limb pain). Median follow-up ranges from a few months to 4 years [23]. For malignant tumors, the 5-year survival rate for patients who have undergone surgical treatment for presacral tumors ranges from 50% to 90% [24]. In benign tumors, surgical intervention does not appear to have an impact on overall survival [23].

6 Conclusions

TGC and rectal GIST are rare, and their diagnosis can be difficult. Once the diagnosis is established, surgical treatment is mandatory. The surgical intervention requires an experienced team in order to avoid tumor violation and ensure an en-bloc excision. A minimally invasive approach may be superior for patients who require a transabdominal approach, provided it can be performed safely and does not offer inferior surgical and oncologic outcomes. Robotic excision of retrorectal tumors is safe and particularly useful in difficult pelvic anatomy when care is taken with patient selection [10].