(Laterally) Extended Endopelvic Resection




BACKGROUND



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Insights in the topology of locoregional tumor spread from developmental biology call for redefining the principles of cancer surgery.1 Surgical procedures translating these concepts into practice have achieved excellent locoregional tumor control at low rates of treatment-related morbidity.2,3,4,5 The corresponding surgical techniques for the therapy of locally advanced and recurrent cancer of the lower female genital tract are termed (laterally) extended endopelvic resection ([L]EER).6 (L)EER enables R0 resection and locoregional tumor control not only in patients who are regarded as suitable candidates for conventional pelvic exenteration but also in patients with tumors fixed to the pelvic sidewall who are currently excluded from exenteration candidacy either pre- or intraoperatively.7




INDICATIONS AND CLINICAL APPLICATIONS



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Pelvic sidewall recurrences or locally advanced cancer of the lower female genital tract have traditionally been considered inoperable. If patients with this clinical presentation have not been irradiated, then radiotherapy or combined chemoradiotherapy can lead to remission. However, in the majority of cases, pelvic sidewall disease is diagnosed following primary or adjuvant pelvic irradiation or has not been controlled by radiotherapy. Consequently, patients with persistent and recurrent cervicovaginal cancer following radiotherapy and patients with advanced primary disease with fistulae between the genital and urinary tracts and/or anorectum are candidates for (L)EER if the following conditions are met preoperatively:





  1. Exclusion of distant metastases,



  2. No tumor involvement at the site of the sciatic foramen, and



  3. Physical status and mental fitness adequate for the megaoperation.




Patients with locally advanced disease without fistulae and patients with postsurgical pelvic recurrence in an non-irradiated pelvis are primarily considered for chemoradiation. However, they may be evaluated for (L)EER if the radiotherapist votes for or the patient requests surgical treatment.




ANATOMIC CONSIDERATIONS



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A prerequisite for the performance of (L)EER is a working knowledge of the ontogenetic anatomy of the pelvis in the human female, which will be briefly outlined here, supplemented by Figures 9-1,2,3. For further details, the reader is referred to textbooks and monographs.8,9,10,11,12




Fig. 9-1.


Anatomic drawings of a transverse section of the female pelvis. (A) Illustrates ontogenetic mapping. (B) The sectioning level is indicated by the inset. Dark yellow, bladder; light yellow, hindgut compartment; dark red, urogenital mesentery; light red, Müllerian compartment; orange, ureters.







Fig. 9-2.


Anatomic drawings of a midsagittal section of the female pelvis. (A) Illustrates ontogenetic mapping. (B) The urogenital ­mesentery with all transit structures has been omitted. However, its area of ectopelvic fusion is shown by the sickle-shaped shadow. Likewise, the central pelvic organs except their most distal parts are cut off. Dark yellow, internal urogenital sinus compartment; light ­yellow, bladder compartment; blue, hindgut compartment; dark red, Müllerian compartment; green, urogenital mesentery; light red, external ­urogenital sinus compartment.







Fig. 9-3.


Topographic anatomy of the pelvic urogenital mesentery. The complex structure of the right pelvic urogenital mesentery at successive states of dissection is highlighted red. (A) Exposure of the posterior peritoneal part above the ureter. Below the ureter the medial surface of the retroperitoneal part is partly visible. (B) Removal of the peritoneal part demonstrates the anterior aspect of the retroperitoneal part. (C) Removal of the perivisceral fat body exposes the anterior aspect of the subperitoneal part. (D) Posterior aspect of the subperitoneal part below the internal iliac artery. (Reproduced with permission from Michael Höckel, MD)





The pelvic ground plan is laid down in the fourth developmental week through migration, proliferation, and specific interaction of cell lineages from the 3 germ layers (endoderm, mesoderm, ectoderm) that establish 3 pelvic building blocks: primitive pelvic wall, terminal gut, and urogenital ridges. Focal interactions of the building blocks lead to the formation of early metacompartments such as the mesonephric ducts-cloaca complex and the cloacal folds and membrane complex. During the embryonic period, late metacompartments are established within the domains of the early metacompartments. These include the mesonephro-urogenital sinus complex and the genital tubercle-cloacal eminence and plate complex. The late metacompartments provide the territory for the definitive compartments, which represent developmental domains independent from each other, thus acting as modules of morphogenesis during the fetal period and thereafter.



Synchronous with the formation of the developmental domains, 3 networks for their support are established from the central primordia: the vascular system from the dorsal aorta, the lymphatic system from the posterior cardinal veins, the nervous system from the spinal neural tube, the spinal neural crest, and the neural cord derived from the caudal eminence. The distal parts of the support system, eg, the lymph capillaries, interact with their recipient compartments and adopt positional information specific for that particular tissue. The proximal parts are conduction structures that transit other compartments within defined corridors.



Differentiation of the pelvic compartments during the fetal period is sex specific. The female endopelvic compartments, hindgut, bladder primordium, and internal urogenital sinus (UGS) develop into the rectum with its mesorectum, the bladder, and the internal UGS compartment. The latter forms the urethra, distal vagina, and distal rectovaginal septum.3 Dorsally, the internal UGS compartment is attached to the anterior rectum and mesorectum (see Figure 9-1). Caudally, it merges with the external UGS compartment (see below).



The mesopelvic compartments include the gonadal primordia, paramesonephric-mesonephric complex, primordial ureter, and primitive urogenital mesentery. These primordia differentiate in the female pelvis into the ovaries with mesovarium, Müllerian compartment, pelvic ureters, and the definitive pelvic urogenital mesentery. Anatomic details of the Müllerian compartment are described elsewhere.2,13 The mature pelvic urogenital mesentery derived from its primitive precursor consists of fibrofatty tissue providing the corridors for the ureter, the pelvic autonomic nerves, the visceral branches of the internal iliac vessel system, the lymph collectors, and, eventually, the intercalated lymph nodes from the Müllerian, bladder, and UGS compartments. The urogenital mesentery also fixes these compartments to the pelvic wall with a structurally complex “mesopelvic suspensorium,” which is fused to the pubo- and iliococcygeus muscles by the arcus tendineus fasciae pelvis anteriorly and to the ischial spine and coccygeus muscles posteriorly (see Figure 9-2). Using the ureter as landmark, the cranial pelvic urogenital mesentery can be formally divided into a supraureteral peritoneal part corresponding to the distal broad ligament and an infraureteral retroperitoneal part loosely attached to the lateral mesorectum. The caudal pelvic urogenital mesentery is located subperitoneally below the level of the obliterated umbilical artery. Laterally, the subperitoneal urogenital mesentery adheres to the perivisceral fat pad and abuts the internal iliac vessel system, proximal sciatic nerve, and sacral plexus. Medially, the subperitoneal urogenital mesentery is continuous with the bladder and the Müllerian parts of the mesometria/mesocolpos (see Figure 9-3).



The ectopelvic compartments are represented by the pelvic epidermis, dermis, hypodermis, fasciomusculoskeletal structures, perivisceral and presacral fat pads,14 as well as the parietal peritoneum. The external UGS compartment matures into all morphologic structures of the vulva except the labia majora, into the gynecologic perineum, and the ventral anal segment.4




PREOPERATIVE PREPARATION



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Box 9-1 KEY SURGICAL INSTRUMENTATION


In addition to a standard laparotomy set and electrosurgical cutting and coagulation devices, the following equipment is useful to perform (L)EER:




  • Table-fixed retractor system (eg, Bookwalter, Codman and Shurtleff, Inc., Raynham, Massachusetts) with rings and blades of various sizes



  • Vessel-sealing system (eg, LigaSure, Valleylab, Boulder, Colorado) of various sizes



  • Cobb periosteal dissectors of various sizes




The locoregional extent of the neoplastic disease is assessed from the clinical examination of the patient under anesthesia during which T2-weighted axial and sagittal high-resolution magnetic resonance imaging (MRI) scans of the pelvis are displayed. Multiple site-directed biopsies are taken and their histopathologic results are awaited. If the pelvic disease is considered treatable with (L)EER by applying the criteria outlined above, positron emission tomography/computed tomography (CT) is ordered to screen for distant metastases. Rarely, diagnostic laparoscopy is necessary to rule out peritoneal carcinomatosis. When distant spread is not obvious, the patient’s comorbidity is checked by the anesthesiologist with regard to fitness for the megaoperation. If all prerequisites are met, then the patient is informed about the putative resective and reconstructive aspects of her treatment.



To prepare the patient for (L)EER, she receives mechanical bowel cleansing the day prior to surgery. Perioperative antibiotic and anticoagulation medication is administered the evening before surgery.




SURGICAL PROCEDURE



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Box 9-2 MASTER SURGEON’S PRINCIPLES




  • The surgeon performing (L)EER should read the patient’s MRI scans herself/himself, optimally in parallel to physically examining the patient



  • The surgeon should be familiar with the ontogenetic anatomy of the female pelvis. She or he should understand the topology of locoregional spread of gynecologic cancer based on embryonic development



  • The surgeon should know the biology of wound healing and the pathophysiology of its disturbance from previous radiotherapy, scarring, and obesity




Principles



The aim of Extended Endopelvic Resection based on ontogenetic anatomy is to resect multiple pelvic developmental compartments instead of tissues related to functions, ie, multiple pelvic viscera. The Müllerian compartment is resected en bloc with the bladder compartment and eventually with the hindgut compartment. Integrated into these multi-compartment resections is the proximal part of the pelvic urogenital mesentery (Figure 9-4). The resection can be caudally expanded by including the internal and external UGS compartments. In these cases, the procedure must be performed both from the abdominal and perineal routes, whereas otherwise solely the abdominal approach is adequate (Figure 9-5).




Fig. 9-4.


Schematic representation of the major types of extended endopelvic resection. (A) Anterior endopelvic resection (transverse plane, circumferential resection line highlighted). (B) Total endopelvic resection (transverse plane, circumferential ­resection line highlighted).







Fig. 9-5.


Schematic representation of the major types of extended endopelvic resection. (A) Abdominal total endopelvic resection (sagittal plane, caudal resection line highlighted). (B) Abdominoperineal total endopelvic resection (sagittal plane, caudal resection line highlighted).






(L)EER includes the distal part of the urogenital mesentery. To ensure the completeness of its caudal resection, the pubo-, ilio-, and coccygeus muscles together with the mesopelvic suspensorium are included in the specimen. Cranial resection of the distal subperitoneal urogenital mesentery necessitates the inclusion of the internal iliac vessel system. Whereas the merging area of the caudal subperitoneal urogenital mesentery with the pelvic wall is defined by the smooth surface of the striated pelvic muscles, the transition of the cranial subperitoneal urogenital mesentery to the internal iliac vessel system and the sacral plexus is complex (Figure 9-6). Consequently, cervicovaginal tumors fixed to the pelvic wall below the sciatic notch level can be reliably resected by the inclusion of these pelvic floor and wall muscles into the en bloc specimen. However, if clinical symptoms or imaging indicate tumor involvement of the pelvic wall at the sciatic foramen, then tumor control can no longer be accomplished with LEER.




Fig. 9-6.


Surgical anatomy of the right pelvic side wall for (L)EER. (A) The urogenital mesentery with all transit structures is removed and the central pelvic organs are cut. (B) Dissection of the caudal part of the distal urogenital mesentery including the pubo-, ilio-, and coccygeus muscles into the (L)EER specimen. (C) Dissection of the rostral part of the urogenital mesentery including the internal iliac vessels into the (L)EER specimen. (D) Dissection of the complete urogenital mesentery including the pubo-, ilio-, and coccygeus muscles and the internal iliac vessels into the (L)EER specimen.




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Jan 12, 2019 | Posted by in GYNECOLOGY | Comments Off on (Laterally) Extended Endopelvic Resection
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