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Keywords:

  • ganglion cells;
  • radical hysterectomy;
  • vesico-uterine ligament

Abstract

  1. Top of page
  2. Abstract
  3. Materials and methods
  4. Results
  5. Discussion
  6. Acknowledgments
  7. References

The aim of this study is to describe the histologic architecture of the tissues corresponding to the surgically developed connective tissue bundle commonly referred to as the posterior leaf of the vesico-uterine ligament (VUL), and to examine distribution of ganglion cells. Serial macroscopic slices, each 15–20 mm in thickness, were made from eight specimens (obtained from six female elderly cadavers). In these macroslices, the location of the deep uterine vein was used to identify the deep leaf of the VUL. The specimens were trimmed and semi-serial histologic sections in thickness were prepared at 1 mm intervals. Vesical veins and the associated nerve elements were enclosed by fascia and formed a common pedicle. The base of the pedicle contained the deep uterine vein trunk. The fascia encircling the pedicle varied in thickness and connective intensity between specimens. This vesical neurovascular bundle contained abundant ganglion cells. On average, 48.0% of the ganglion cells along the vesical tributaries of the deep uterine vein were located on the medial or vaginal side of the veins, 19.2% were located between veins, 13.0% on the lateral side of the veins, and 19.8% on the dorsal side. The interindividual variability was greatest on the dorsal side of vesical veins and ranged 11–202 cells. We conclude that in order to achieve maximal preservation of the ganglion cells during the surgical dissection of the posterior leaf of the VUL, care must be taken when the medial or vesical aspect of the ligament is separated. The standard nerve-sparing radical hysterectomy should be modified to reflect differences in the distribution of ganglion cells and in connective intensity between ganglions and veins.

Most drainage from the urinary bladder, uterine cervix, and proximal vagina passes through a common venous drainage system, which consists of the deep uterine vein and numerous unnamed tributaries. Gynecological surgeons resect these veins as part of the vesico-uterine ligament (VUL) and paracolpium in radical hysterectomies. These regions are not defined by classical anatomy but rather are surgically developed structures that carry multiple names and are defined by individual surgeons(1,2). Herein, we define the posterior leaf of the VUL as a surgically developed connective tissue bundle along the deep uterine vein. Recently, we demonstrated using an electrostimulation technique during surgery that the vesical detrusor nerves run on the dorsal side of the VUL and along the posterior leaf of the VUL(3). The nerve component in this area is not a simple conductive system but also contains ganglion cells. The removal of large numbers of these cells from the posterior leaf of the VUL, as sometimes occurs in nerve-sparing radical hysterectomies, results in worse postsurgical urodynamic analyses(4). The usual surgical excision of the deep veins is conducted under the premise that the nerves and veins run independently. The veins are usually ligated and cut as part of a connective tissue bundle that is designated as the posterior leaf of the VUL(5–7). However, to our knowledge no studies have been conducted to confirm whether the vesical nerves in the VUL form a neurovascular bundle with the drainage veins.

The aims of the present study were to describe the histologic architecture of the VUL with particular attention to defining the topographical relationship between the veins and nerve components in the posterior leaf of the VUL and to propose an improvement to the procedure for resecting the deep uterine vascular pedicle in nerve-sparing radical hysterectomy.

Materials and methods

  1. Top of page
  2. Abstract
  3. Materials and methods
  4. Results
  5. Discussion
  6. Acknowledgments
  7. References

The pelvic viscera, including the urinary bladder, uterine cervix, proximal vagina, distal ureter, and urethra were removed from six formalin-fixed female donated cadavers (60–85 years old). In the dissection, the hypogastric and pelvic splanchnic nerves were identified on the dorsal side of the specimen and the uterine artery and deep uterine vein labeled near the distal ureter. From the six pelvic soft tissues, we obtained eight specimens (six right sides and two left sides) for histology. First, nearly frontal serial slices, 15–20 mm in thickness, were made macroscopically according to Tamakawa et al.(8). The aforementioned “nearly frontal plane” was tilted almost 30 degrees anteriorly and was similar to a plane used to display clear-cut topographical relations of the female pelvic viscera labeled as “the bladder at the second floor,”“the vagina at the first floor,” and “the rectum at the ground floor”(9). We used the gross topographical relations among the pelvic viscera and related structures to precisely identify and localize the histologic sections of the posterior leaf of the VUL. Next, those slices including the posterior leaf of the VUL were trimmed and prepared for paraffin-embedded histology with slices of 3 μm in thickness cut at 1 mm intervals. Finally, we attempted to obtain paraffin sections along nearly the entire course of the vesical veins. Hematoxylin and eosin staining was performed on all sections. We classified the ganglion cell clusters into four groups concerning the procedure of nerve-sparing radical hysterectomy according to their sites: the medial, lateral, intervenous, and dorsal groups (Figs. 1, 2) and counted the number of ganglion cells. The study was undertaken within the provisions of the Declaration of Helsinki 1995 (as revised in Edinburgh 2000). The project did not include a specific protocol that warranted examination and approval by the institutional ethics committees.

image

Figure 1. A) Four ganglion groups we classified in operative procedure (dissecting the posterior leaf of VUL), side view; •: medial, inline image: intervenous, □: dorsal. B) Overview; •: medial, inline image: intervenous, ▴: lateral.

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image

Figure 2. A) Schema of four ganglion groups, side view; 1: medial, 2: intervenous 3: lateral, and 4: dorsal. B) Schema of four ganglion groups in histologic section, 1: medial, 2: intervenous 3: lateral, and 4: dorsal.

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Results

  1. Top of page
  2. Abstract
  3. Materials and methods
  4. Results
  5. Discussion
  6. Acknowledgments
  7. References

We identified the posterior leaf of the VUL that contained the vesical neurovascular bundle and numerous ganglion cell clusters (Figs. 3, 4). These ganglion cells displayed a homogeneous morphology consisting of large, eosinophilic cells with a maximum diameter of 25–30 μm. They were found along the nerve fiber bundles as well as in round or oval “ganglia” surrounded by a connective tissue sheath. Neuron cell numbers per ganglion varied significantly among sites and individuals. The total number of ganglion cells ranged 389–732 (mean, 561) among the eight specimens. Table 1 lists the localization of the ganglion cells in the vesical neurovascular pedicle. On average, 48.0% of the ganglion cells (273.4 cells) along the vesical tributaries of the deep uterine vein were located on the medial or vaginal side of the veins and were classified as “medial,” 19.2% (109.1 cells) were located between veins and were classified as “intermediate,” 13.0% (74.0 cells) were on the lateral side of the veins, and 19.8% (112.9 cells) on the dorsal side of the veins (Table 1). The interindividual variability was greatest on the dorsal side of the vesical veins with the cell number ranging 11–202 cells. We obtained bilateral samples from two individuals. Interestingly, there was a considerable difference between the left and right sides for the same cadaver in the medial and dorsal groups. In specimen case 1, Table 1, this difference was almost threefold.

image

Figure 3. Histology along the entire course of the vesical tributaries of the deep uterine vein and the associated ganglion cell cluster. A sample obtained from a 60-year-old female cadaver. Panel A exhibits a vesical neurovascular pedicle attaching to the parietal fascia (arrowheads) and running toward the urinary bladder. The parietal fascia covers the levator ani (LA). The associated nerve elements are indicated in red (arrows, ganglion cell clusters: see panels B, C, and D). DUV, the base of the pedicle of the deep uterine vein trunk. Panels B, C, and D is a higher magnification view of a square with (B, C, D) in panel A. The ganglion cells display a homogeneous, eosinophilic morphology.

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image

Figure 4. Histology of the base of the deep uterine vein neurovascular bundle with an unclear ventrolateral demarcation. A sample different from that shown in Fig. 3 (69-year-old cadaver). This neurovascular pedicle is thick because of the dilated vesical veins (asterisks). In contrast to the vesical side of the pedicle, the dorsolateral or rectal side is clearly demarcated from the mesorectum (MR) by a fascial layer (arrowheads). The associated nerve elements are indicated in red (arrows, ganglion cell clusters: see panel B, C). Panels B and C are higher magnification view of square with B and C in panel A. Other abbreviations are the same as in Fig. 3.

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Table 1.  Distribution of ganglion cells
Case1 right1 left234 right4 left56Mean n (%)
Medial316106273231459322225255273.4 (48.0)
Lateral101167273676773474.0 (13.0)
Intervenous14815892111605615098109.1 (19.2)
Dorsal16750179119843153202112.9 (19.8)
Total732491571389693498562 

We then examined the relationship between the posterior leaf of VUL and the endopelvic fascia. The superior or intrapelvic surface of the levator ani was covered by a definite layer of parietal fascia corresponding to the endopelvic fascia defined by urologists(10). The terminal portion of the deep uterine vein was clearly covered by the parietal fascia (Fig. 3). The vesical veins and tributaries of the deep uterine vein formed a neurovascular bundle with abundant nerve elements. The nerve fibers, both myelinated and unmyelinated, accompanied the vesical veins. The neurovascular bundle tended to be encircled by a fascial layer that was continuous with the parietal fascia. The fascia encircling the pedicle varied in thickness between specimens on the vesical or ventrolateral side of the deep uterine vein trunk. In two of eight specimens, the vesical neurovascular bundle made a distinct pedicle that was contained in a single histologic slice (Fig. 3). In the six remaining specimens, 19–26 histologic sections (19–26 mm) were needed to include the entire pedicle connecting between the parietal fascia and the bladder because the ventrolateral margin of the pedicle base was not clearly demarcated (Fig. 4).

Discussion

  1. Top of page
  2. Abstract
  3. Materials and methods
  4. Results
  5. Discussion
  6. Acknowledgments
  7. References

Our dissections demonstrated that the vesical neurovascular bundle contained abundant ganglion cells, which were most prominent on the medial and dorsal sides of the veins. The distribution of pelvic ganglion cells is well described in male cadavers(10); however, information in the female is limited. Ganglion cells have been identified in the paracolpium(11) and sacrouterine ligament(12). Although autonomic nerves are present in the dorsal part of the deep layer of the VUL(13,14), the presence of ganglions has not been studied.

It is important to preserve ganglion cells during surgery because they do not recover well following injury, and loss of cell function contributes to poor urodynamic outcomes. Of the four groups of ganglion cells located along and around the deep uterine vein tributaries, the intervenous and lateral groups were most difficult to preserve during the dissection (Figs. 1, 3, 4). However, the medial and dorsal groups, which accounted for just over two thirds of the cells, were easier to separate from the veins. Gynecologists do not always successfully separate the nerve elements from the deep uterine vein tributaries. This is primarily because the common venous drainage of the bladder, cervix uteri, and proximal vagina make preserving this fascial space a challenge, particularly since crossing this space with the surgical plane is unavoidable.

The posterior leaf of the VUL is a surgically developed structure and not an anatomical entity. The surgical plane for the vaginal side of the posterior leaf of the VUL is particularly inconsistent with variations between surgeries, surgeons, patients, and even different sides in the same patient. Previous reports emphasized a need for the lateral displacement of the pelvic plexus(7) and separation between the lateral nerve portion and medial vascular portions of the deep layer of the VUL(15) in nerve-sparing radical hysterectomy. These reports did not consider the medially located nerve and ganglion component. In our study, 48.7% of ganglion cells along the vesical tributaries of the deep uterine vein were located on the medial or vaginal sides of the veins; and these were comparatively easier to separate from the vasculature. Additionally, dissection of the fatty connective tissue in the posterior part of the VUL, after cutting of the vesical vein, has also been advocated(5). Though this step may be important in some patients, is it necessary in all cases? Our present data show that in cases with abundant ganglion cells in the dorsal area of the veins, autonomic nerves and ganglion cells are spared on the proximal vagina, without dissection of the medial nerve part of the vesico-uterine ligament. For example, in cases 2 or 6, when only a short length of vaginal wall was removed, separation of the medial nerve group from the paracolpium was not necessary. In contrast, in cases with few ganglion cells on the dorsal side of vesical veins, such as in case 3, or in a case where more extensive vaginal removal is necessary, it is difficult to spare the autonomic nerves by a conventional nerve-sparing procedure. In such cases, additional steps may be needed to preserve the medial nerve element.

The necessity of the dissection of the posterior leaf of the vesico-uterine ligament is controversial. Hockel et al.(16) reported local tumor spread is confined to the Müllerian morphogenetic unit in patients with cervical cancer and the vesical vessels and the main pelvic autonomic nerve plexus are different tissue units. Their results revealed that no significant changes were detected with respect to lower urinary tract function (maximum detrusor pressure at micturition, maximum flow rate, and so on)(17), but individual data of urodynamic study was unclear. Present study revealed that most cases had many ganglion cells on the dorsal side of vesical veins, so the autonomic nerves and ganglions might be able to be preserved by their methods. There were big interindividual difference and left–right difference of ganglion distribution in the present study, but the numbers in this study were restricted. Further studies are needed in order to clarify the existence and significance of their difference.

Our intraoperative electrical stimulation method may be useful in nerve-sparing radical hysterectomy to verify the presence of ganglion or autonomic nerves in the dorsal area. We propose that the methodology of nerve-sparing radical hysterectomy should be modified to account for differences in ganglion distribution judged by intraoperative electrical stimulation. In cases that react to stimulation on the dorsal side of vesical veins, autonomic nerves and ganglions will be preserved exclusively with lateral displacement of the pelvic plexus. In cases failing to react, lateral displacement alone could result in the ganglions being included in the clamped and resected area. Thus, the medial side may also need to be dissected for nerve sparing. Anatomically, preservation of the medial nerve element depends on the clear separation of the paracolpium from the proximal vagina. A clear fascia demarcating the ventral margin of the mesorectum known as Denonvilliers’ fascia(18–20) corresponds to the rectovaginal septum in gynecological terms. Our findings suggest that Denonvilliers’ fascia is continuous with the fascial layer enclosing the deep uterine vein tributaries, connects to the parietal fascia covering the levator ani, and provides the dorsal margin for dissection. The dorsolateral extension of Denonvilliers’ fascia separates the mesorectum from the pelvic nerve plexus and hypogastric nerve(21). The ganglion cells shown in the present study were located on the peripheral side of the pelvic plexus along the pre- and postganglionic nerve courses. Thus, it is likely that the deep uterine vein tributaries and associated nerve elements are most likely to be included in the same fascial space as the pelvic plexus. This was not, however, confirmed in this study since our dissections did not extend to such superior or proximal levels of the pelvis.

Dissection of the medial nerve component may be an effective means of sparing pelvic autonomic innervation in some cases of nerve-sparing radical hysterectomy. This technique does, however, have some limitations. We did find differences in the connective intensity (tight or loose) between ganglions and veins. In cases with tight connections, separation was difficult and the ganglions may have been injured. The effect on ganglion function, however, was not assessed. Additionally, it may be difficult to spare nerve function without compromising operative radicality. Further studies are needed to evaluate the radicality of this procedure and whether postoperative bladder function is affected from a urodynamic standpoint.

Acknowledgments

  1. Top of page
  2. Abstract
  3. Materials and methods
  4. Results
  5. Discussion
  6. Acknowledgments
  7. References

Grant-in-aid for scientific research on priority area from the Ministry of Education, Science, Sports, and Culture; grant-in-aid from the Ministry of Health, Labor and Welfare, Japan; the 21st century COE Program Special Research Grant (Tohoku University) from the Ministry of Education, Science, Sports, and Culture, Japan.

References

  1. Top of page
  2. Abstract
  3. Materials and methods
  4. Results
  5. Discussion
  6. Acknowledgments
  7. References
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