Lymphadenectomy
INTRODUCTION
Surgical staging including lymph node dissection is the cornerstone of treatment of early-stage endometrial and ovarian malignancies. In 1988, surgical staging replaced clinical staging for endometrial cancer, due to inherent underreporting of metastatic disease distribution in the clinical staging system. Comprehensive staging guides treatment planning for subsequent chemotherapy and/or radiation therapy. In the setting of advanced or recurrent disease, lymph node dissection may be undertaken for the purpose of removing bulky tumor. Although cervical cancer is staged clinically, lymph node dissection plays a role in the management of early-stage tumors.
The lymphatic drainage of the uterus, tubes, and ovaries follows the blood supply of these organs and includes the pelvic lymph node basins as well as the aortic lymph nodes (Figure 28-1). Depending on the site of malignancy and the clinical indications, lymph node dissection may be undertaken in some or all of these basins, either unilaterally or bilaterally.
FIGURE 28-1. Pelvic and aortic lymph node basins. (Redrawn, with permission, from Chi DS, Bristow RE, Gallup DG. Surgical principles in gynecologic oncology. In: Barakat RR, Markman M, Randall ME, eds. Principles and Practice of Gynecologic Oncology. Baltimore, MD: Lippincott Williams & Wilkins; 2009:270.)
PELVIC LYMPH NODE DISSECTION
Procedure Overview
Box 28-1 Master Surgeon’s Corner
Adequate exposure and identification of anatomic structures are crucial to avoid injury to adjacent structures of the pelvic sidewall.
Proper development of the paravesical and pararectal spaces is an essential step prior to beginning the process of removing lymph nodes.
Appropriate use of hemostatic clips and vesselsealing devices (ie, limiting the use of monopolar cautery and blunt dissection) may reduce the risk of lymphorrhea.
Indications and Historical Perspective
There is a generalized lack of standardization in the technique of pelvic lymphadenectomy in gynecologic cancer that is apparent in both the literature and surgical practice. With the exception of sentinel lymph node mapping, the total number of lymph nodes removed is most often used as a surrogate for the radicality and completeness of the procedure. Cibula and Abu-Rustum1 recently attempted to clarify and standardize the terminology and anatomic basis for the procedure, proposing a new anatomically based classification system for pelvic lymphadenectomy. In this system, a complete systematic lymphadenectomy or “type III dissection” includes the removal of all fatty lymphatic tissue from the predicted areas of high incidence of lymph nodes with metastatic involvement. This comprehensive procedure is described later in this chapter and includes dissection of the 5 main anatomic regions of the pelvic lymphatic drainage: external iliac, obturator, internal iliac, common iliac, and presacral lymph nodes. In certain circumstances, more limited dissection may be indicated, such as sentinel lymph node biopsy, excision of only bulky nodes, or lymph node sampling.
Several operative approaches may be used for the pelvic lymph node dissection. It is often performed via laparotomy at the time of open hysterectomy or laparoscopically at the time of total laparoscopic hysterectomy or laparoscopic-assisted vaginal hysterectomy. In some cases, it is performed as part of a secondary staging procedure, which often may be accomplished laparoscopically. In addition, the technique of pelvic sentinel lymph node mapping may be used in selected cases. The equipment required varies by the operative approach, as described later.
Preoperative Preparation
Patient Evaluation and Work-Up
Prior to surgery, the patient should undergo a complete history and physical, complete blood count, basic metabolic panel, coagulation profile, pregnancy test, electrocardiogram, and chest radiograph (when indicated by the patient’s age).
Consent Considerations
In addition to the standard risks of general anesthesia and abdominal surgery, a discussion of procedure-specific risks is warranted, including chronic lymphedema, lymphocele potentially requiring further medical or surgical treatment, and injury to adjacent nerves, vascular structures, and the ureter.
Patient Preparation
A preoperative bowel preparation may be helpful to decompress the bowel and facilitate exposure. Epidural anesthesia may be offered for open procedures, which may optimize postoperative pain control while reducing the adverse effects of intravenous opioid analgesia. As with any open procedure, a single dose of prophylactic antibiotics should be administered intravenously within 60 to 120 minutes of the initial skin incision.
Operative Procedure
Box 28-2 Caution Points
Careful placement of lateral retractors without exertion of excessive pressure on the psoas muscle will avoid potential injury to the femoral nerve.
Careful identification of the genitofemoral and obturator nerves is essential to avoid injury, and the use of electrocautery should be minimized in close proximity to these fine nerve structures.
Retraction on the external iliac vein during the obturator dissection must be applied gently to avoid intimal injury and minimize the risk of subsequent deep vein thrombosis.
Careful dissection is particularly important in the obturator space to avoid bleeding from the corona mortis.
Open Pelvic Lymph Node Dissection
The procedure may be performed in the supine position, although it is usually combined with hysterectomy requiring the dorsal lithotomy position. A Foley catheter is placed. While a pelvic lymph node dissection may sometimes be adequately performed through an extended transverse incision (eg, Maylard or Cherney), maximal exposure is obtained with a vertical midline approach, particularly in the obese patient or if dissection of the deep common iliac lymph nodes is required. Standard laparotomy equipment is required for an open dissection, including a self-retaining retractor (eg, Bookwalter). In addition to standard instrumentation, Penfield dissectors may be useful in cases with adherent lymphadenopathy (Figure 28-2).
FIGURE 28-2. Penfield dissectors.
Opening the Pelvic Peritoneum
The round ligament is clamped and divided, and the umbilical ligament is isolated. Working parallel to the round ligament, the peritoneum is incised with Metzenbaum scissors or electrocautery in a linear fashion between the round ligament and the umbilical ligament to the reflection of the anterior abdominal wall.
Development of the Paravesical Space
The umbilical ligament is retracted medially to facilitate blunt dissection of the paravesical space, exposing the external iliac nodes, obturator space, and ventral aspect of the hypogastric vessels.
Identification of the Ureter
The ureter should be clearly identified as it crosses the bifurcation of the common iliac artery into the internal and external iliac artery, and courses along the medial leaflet of the broad ligament. A vessel loop may be placed around the ureter for gentle retraction and continued identification throughout the procedure.
Development of the Pararectal Space
The peritoneal incision is extended cephalad along the psoas muscle, lateral and parallel to the infundibulo-pelvic ligament. Next, the infundibulopelvic ligament (if not already divided) and ureter are retracted medially, and the hypogastric artery is identified. The pararectal space is then developed bluntly, retracting the rectum medially and providing access to the hypogastric nodes and obturator space.
External Iliac Lymph Node Dissection
The dissection begins with the external iliac lymph nodes. A Singley (ringed) forceps may be used to gently grasp the lymphatic tissue without fracturing the nodes. Sharp or blunt dissection with Metzenbaum scissors is used to isolate small blood vessels and lymphatic channels, which are secured with hemostatic clips and divided. The lateral border of the dissection is the genitofemoral nerve. Moving from lateral to medial, the nodal tissue is dissected first from the psoas muscle and then the external iliac vessels, taking care to protect the genitofemoral nerve and the external iliac artery and vein. The cephalad limit of the external iliac dissection is the bifurcation of the common iliac artery, and the caudal limit is the deep circumflex iliac vein, a branch of the external iliac vein that is usually seen coursing anteriorly over the external iliac artery. Lymph nodes caudal to the deep circumflex iliac vein predominantly drain the lymphatics of the lower extremity, and their removal may increase the risk of lymphedema.
Obturator and Hypogastric Lymph Node Dissection
The obturator and hypogastric lymph nodes may be accessed from a medial or a lateral approach, and many surgeons use a combined approach. Beginning with a medial approach, the external iliac vein is gently pulled laterally with a vein retractor, and the nodal package posterior to the vein is grasped with the Singley forceps. Gentle dissection is used to identify the obturator nerve, and the nodal package between the vein and nerve is dissected free. Next, additional nodes may be removed from below the nerve. Care should be taken to avoid injury to the obturator vessels and anastomotic obturator or pubic veins, which may sometimes be encountered in the distal portion of the obturator space. This area has been referred to as the “corona mortis,” or ring of death, due to the potentially treacherous plexus formed by variable anastomotic veins that are often found linking the obturator and external iliac venous systems. A 4-part “ring” may be formed by the external iliac vein, hypo-gastric vein, obturator vein, and anastomotic obturator or pubic vein (Figure 28-3).
FIGURE 28-3. Corona mortis. The anastomotic obturator or pubic vein is seen crossing the distal obturator space and entering the left external iliac vein.
The hypogastric nodes may then be dissected from the proximal portion of the umbilical ligament, moving cephalad over the hypogastric artery and the origin of the uterine artery. Finally, the external iliac vessels are bluntly mobilized medially from the psoas muscle, allowing access to the obturator space from a lateral approach, to remove any remaining nodal tissue from behind and beneath the vessels, particularly near the common iliac artery bifurcation.
Common Iliac Lymph Node Dissection
In a type III pelvic lymph node dissection as described by Cibula and Abu-Rustum,1 the common iliac dissection includes removal of the superficial and deep common iliac lymph nodes. The common iliac lymph nodes receive lymphatic vessels from 2 major lymphatic trunks draining the uterus and cervix. A superficial trunk enters the pelvis via the femoral canal, courses along the ventral aspect of the external iliac vessels, receives branches from the parametrium, and continues along the ventral aspect of the common iliac artery (Figure 28-4). On the right side of the pelvis, these lymphatics continue toward the precaval and interaortocaval regions; on the left side of the pelvis, they continue to the left para-aortic region.
FIGURE 28-4. Pelvic lymphatic drainage: the superficial lymphatic trunk. (Redrawn, with permission, from Cibula D, Abu-Rustum NR. Pelvic lymphadenectomy in cervical cancer: surgical anatomy and proposal for a new classification system. Gynecol Oncol. 2010;116:33-37.)
A deep trunk also enters the pelvis via the femoral canal but follows a more medial course, surrounding the obturator nerve and receiving parametrial lymphatics before entering the common iliac area (Figure 28-5). This deep trunk then divides into 2 branches. A lateral branch courses between the common iliac vein and the psoas muscle, forming the deep common iliac nodes before entering the paracaval region. A medial branch tunnels beneath the common iliac vessels to the medial aspect of the vessels and enters the presacral area, forming the presacral nodes, before coursing toward the interaortocaval and preaortic regions.
FIGURE 28-5. Pelvic lymphatic drainage: the deep lymphatic trunk. (Redrawn, with permission, from Cibula D, Abu-Rustum NR. Pelvic lymphadenectomy in cervical cancer: surgical anatomy and proposal for a new classification system. Gynecol Oncol. 2010;116:33-37.)
The common iliac dissection begins with careful removal of the superficial common iliac lymph nodes from the ventral and lateral surfaces of the common iliac artery and vein. Next, the deep common iliac lymph nodes (formed by the lateral branch of the deep lymphatic trunk) are identified between the common iliac vein and the psoas muscle. These are carefully removed. The cephalad limit of the dissection is the aortic bifurcation, and the lateral border is the psoas muscle. The floor of the dissection will expose the lumbosacral trunk and the obturator nerve.
Presacral Lymph Node Dissection
The presacral lymph nodes are found on the anterior surface of the sacrum between the common iliac veins and receive lymphatics from the medial branch of the deep lymphatic trunk. These lymph nodes are carefully removed, with particular care taken to avoid injury to the left common iliac vein.
Laparoscopic Transperitoneal Pelvic Lymph Node Dissection
The patient is placed in the dorsal lithotomy position with the legs placed in Allen stirrups. A Foley catheter is inserted, and an orogastric tube is placed by the anesthesiologist to provide gastric decompression. After initial trocar placement, the patient is placed in steep Trendelenburg position. Suggested equipment for the laparoscopic approach includes a 10-mm blunt port, two 5-mm trocars, a 5/10-mm trocar, 5- and 10-mm laparoscopic clip appliers, 5-mm graspers, and a 10-mm lymph node spoon. For dissection, we use a monopolar cautery device; a vessel-sealing device is also used. The procedure may be performed using a variety of available monopolar cautery devices for dissection and a vessel-sealing device.
Trocar Placement
Using an open laparoscopy technique, a blunt 10-mm trocar is placed in the umbilicus, and the abdomen is insufflated (Figure 28-6). Under direct visualization, two 5-mm trocars are placed in the right and left lower quadrants, at a point approximately 1 cm superior to and 1 cm medial to the anterior superior iliac spine. Care should be taken to avoid injury to the inferior epigastric vessels. A 5/10-mm trocar is placed in the suprapubic area, carefully avoiding injury to the bladder. Individual trocar size and placement may vary depending on planned concurrent procedures, choice of instrumentation, the patient’s habitus, and prior surgical history.
FIGURE 28-6. Trocar placement for laparoscopic pelvic and aortic lymph node dissection. (Redrawn, with permission, from Abu-Rustum NR, Sonoda Y. Transperitoneal laparoscopic staging with aortic and pelvic lymph node dissection for gynecologic malignancies. Gynecol Oncol. 2007;104[suppl]:S5-S8.)
Development of the Paravesical Space
Using the surgeon’s chosen instrument, the round ligament is divided, and the umbilical ligament is isolated. Working parallel to the umbilical ligament, the peritoneum is incised in a linear fashion between the round ligament and the umbilical ligament to the reflection of the anterior abdominal wall. Gentle medial traction is then applied to the umbilical ligament, and the paravesical space is developed with a blunt instrument.
Development of the Pararectal Space
The ureter should be clearly identified as it crosses the bifurcation of the common iliac artery and courses along the medial leaflet of the broad ligament. The peritoneal incision is extended cephalad along the psoas muscle, parallel to the infundibulopelvic ligament. Next, the infundibulopelvic ligament (if not already divided) and ureter are retracted medially, the hypogastric artery is identified, and the pararectal space is developed bluntly, retracting the rectum medially and providing access to the hypogastric nodes and obturator space.
External Iliac Lymph Node Dissection
The dissection begins with the distal common iliac lymph nodes, lateral to the common iliac artery, and moving caudal to the external iliac lymph nodes. Laparoscopic graspers are used to protect the ureter medially and provide gentle traction on the nodal package. The monopolar cautery device may be used as both a blunt dissector and a cautery device to isolate small blood vessels and lymphatic channels, which are secured with hemostatic clips and divided. Larger vessels may be transected with a vessel-sealing device. Moving from lateral to medial, the nodal tissue is dissected first from the psoas muscle and then the external iliac vessels, taking care to protect the genitofemoral nerve and the external iliac artery and vein. The caudal limit of the dissection is the deep circumflex iliac vein, a branch of the external iliac vein that is usually seen coursing anteriorly over the artery. The nodes may be removed atraumatically from the abdomen using a 10-mm laparoscopic spoon.
Obturator and Hypogastric Lymph Node Dissection
The obturator nodal package, located posterior to the external iliac vein, is grasped gently and retracted medially. Gentle blunt dissection is used to identify the obturator nerve, and the nodal package between the vein and nerve is dissected free, using clips and cautery as necessary to divide small vessels and lymphatics. Additional nodes may be removed from below the nerve, taking extreme care to avoid injury to the obturator vessels and potential anastomotic pelvic veins, which may sometimes be encountered in the distal portion of the obturator space. The hypogastric nodes may then be dissected from the proximal portion of the umbilical ligament, near the origin of the uterine artery. Finally, the iliac vessels are gently dissected medially off of the psoas muscle, allowing lateral access to the obturator space to remove any residual nodal tissue. The specimen is removed using the laparoscopic spoon.
The completed dissection of the pelvis exposes the ureter, medial aspect of the external iliac vessels, ventral aspect of the hypogastric vessels, and superior part of the obturator space, exposing the obturator vessels and nerve (Figure 28-7).
FIGURE 28-7. Completed laparoscopic pelvic lymph node dissection. The completed dissection of the right pelvis exposes the ureter, medial aspect of the external iliac vessels, ventral aspect of the hypogastric vessels, and superior part of the obturator space, exposing the obturator vessels and nerve.
Sentinel Lymph Node Mapping and Dissection
The technique of sentinel lymph node mapping in early-stage cervical and uterine malignancy may be used in selected cases.2 A cervical blue dye injection is administered in the operating room prior to beginning the case. This may be performed at the time of examination under anesthesia, or it may be performed after skin preparation and draping. Although methylene blue 1% solution may be used, we generally use isosulfan blue 1% (Lymphazurin), a sterile aqueous solution packaged in 5-mL vials that requires no refrigeration or special preparation. Mild adverse reactions to isosulfan blue may occur in a small number (< 1%) of patients, consisting of localized swelling or pruritus of the neck, abdomen, hands, or feet. Severe anaphylactic reactions are rare but have been reported with similar compounds. Use is contra-indicated in patients with a known hypersensitivity to phenylethane compounds. A transient idiosyncratic decrease in the pulse oximeter reading is common immediately after the injection and represents detection of the blue dye in the circulation rather than actual hypoxemia. Blue-tinged urine is frequently noted for up to 24 hours after surgery.
The cervical injection may be performed with a spinal needle, and a tenaculum placed on the anterior lip of the cervix may be used for traction. A total of 4 mL of blue dye is injected into the cervical stroma, with 2 mL injected at each of the 3 o’clock and 9 o’clock positions. It is important to inject the dye into the cervical stroma, with approximately 1 mL injected deeply and 1 mL injected superficially. This approach avoids excessive staining of the bladder flap and targets the parametrial lymphatic drainage. If gross cervical tumor is present, the dye should be injected into the cervical stroma adjacent to the lesion.
The procedure then continues as planned, either via laparoscopy or laparotomy. The lymph node mapping is usually visible transperitoneally upon entering the pelvis, and the sentinel lymph node dissection is then performed in an expeditious manner to avoid excessive dissipation of the dye. The pelvic sidewalls are opened in the usual manner, the ureter is identified, and the paravesical and pararectal spaces are developed. Blue lymphatic channels are often seen coursing along the uterine vessels and crossing the hypogastric artery before draining into the external iliac and hypogastric lymph nodes (Figure 28-8). The first blue node noted along the drainage pathway is removed and designated as the sentinel node. Additional blue nodes may sometimes be identified and designated as secondary sentinel lymph nodes.
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