Latex-casting of vessels relevant during vaginectomy in bitches Latex-opspuitingen van bloedvaten die relevant zijn tijdens vaginectomie bij de teef

Vaginectomy is an infrequently performed invasive surgery to control vaginal disorders in bitches. Indications for vaginectomy include vaginal tumors (leiomyoma, fibroleiomyoma and leiomyosarcoma), polyps and vaginal prolapse. The surgical technique is a two-step procedure and consists of an extended laparotomy approach with caudal ovariohysterectomy followed by an episiotomy approach with removal and reconstruction of the vaginal wall. Although the surgery itself is invasive, the combined approach results in a favorable outcome with an apparently low risk of intraand postoperative complications. During vaginectomy, traction is placed on the vagina and its supplying blood vessels via the episiotomy site. By means of a post-mortem study of five dogs, it was investigated if this traction resulted in damage or rupture of the supplying vessels. In this study, it was demonstrated that the uterine branch of the vaginal artery and the caudal vesical artery rupture during the traction phase of a vaginectomy via the episiotomy site. Rupture of these vessels might result in insufficient perfusion of the bladder and extensive intraabdominal and -pelvic bleeding.


Vaginectomy is an infrequently performed invasive surgery to control vaginal disorders in bitches. Indications for vaginectomy include vaginal tumors (leiomyoma, fibroleiomyoma and leiomyosarcoma), polyps and vaginal prolapse. The surgical technique is a two-step procedure and consists of an extended laparotomy approach with caudal ovariohysterectomy followed by an episiotomy approach with removal and reconstruction of the vaginal wall. Although the surgery itself is invasive, the combined approach results in a favorable outcome with an apparently low risk of intra-and postoperative complications. During vaginectomy, traction is placed on the vagina and its supplying blood vessels via the episiotomy site. By means of a post-mortem study of five dogs, it was investigated if this traction resulted in damage or rupture of the supplying vessels. In this study, it was demonstrated that the uterine branch of the vaginal artery and the caudal vesical artery rupture during the traction phase of a vaginectomy via the episiotomy site.
Rupture of these vessels might result in insufficient perfusion of the bladder and extensive intraabdominal and -pelvic bleeding.

INTRODUCTION
Over 80% of the reported vaginal tumors are benign smooth muscle tumors (Brodey and Roszel, 1967;Herron, 1983;Thacher and Bradley, 1983;Kydd and Burnie, 1986). Most are leiomyomas and fibroleiomyomas, but also fibromas and polyp formations may occur (Brodey and Roszel, 1967;Thacher and Bradley, 1983). Benign vaginal tumors are most often intraluminal and pedunculated, originating from the vaginal wall (Nelissen and White, 2012). Malignant tumors are less frequently observed and include leiomyosarcomas, carcinomas and transmissible venereal tumors (Hill et al., 2000;Nelissen and White, 2012). Transmissible venereal tumors occur worldwide but are mostly diagnosed in tropic and subtropical regions where they represent 37 to 60% of the malignant tumors (Brodey and Roszel, 1967;Thacher and Bradley, 1983). In Western Europe, leiomyosarcoma is the most common malignant vaginal neoplasia (Hill et al., 2000;Chiers, 2017). Most malignant tumors have, in contrast to benign tumors, a rather broad base and show an infiltrative growth (Farese et al., 2008;Tivers and Baines, 2010;Nelissen and White, 2012).
The treatment of non-pedunculated vaginal neoplasia consists of a (sub)total vaginectomy (Hill et al., 2000;Salomon et al., 2004;Tivers and Baines, 2012). This technique includes the removal of the complete vagina or the part of the vaginal wall surrounding the vaginal mass. In the intact bitch, a complete removal of the female genital tract is performed prior to vaginectomy (Nelissen and White, 2012). This additional surgical intervention is advised due to the oestrogendependent characteristics of vaginal leiomyomas (Brodey and Roszel, 1967;Thacher and Bradley, 1983;Kydd and Burnie, 1986). Compared to the 15%-recurrence rate in intact bitches, a zero-recurrence rate of leiomyomas has been observed when ovariohysterectomy is simultaneously performed at the time of the tumor removal (Nelissen and White, 2012;Saba and Lawrence, 2012;Weissman et al., 2013). Most benign tumors are good candidates for local resection via episiotomy given their biological behavior and because they are mostly pedunculated (Thacher and Bradley, 1983;Nelissen and White, 2012). Malignant tumors on the other hand require a more extensive surgical resection as a consequence of their broad base and strong infiltrative nature (Kapatkin et al., 1992;Nelissen and White, 2012). The treatment of malignant vaginal neoplasia requires total vaginectomy techniques combining an episiotomy approach with laparotomy. If necessary, these techniques can be further augmented by ostectomy or pubic osteotomy (Igna et al., 2016).
Vaginectomy performed through laparotomy combined with episiotomy results in few intra-and postoperative complications (Kyles et al., 1996;Gower et al., 2008;Nelissen and White, 2012;Alonge et al., 2015;Igna et al., 2016). As for intraoperative complications, hemorrhage is most frequent and might result in substantial blood loss (Prassinos et al., 2010). However, this complication is most of the time promptly managed and resolved by coagulation of the damaged vessel through the episiotomy approach (Nelissen and White, 2012). The most frequently observed postoperative complication is serohemorrhagic discharge, presumably originating from minor residual vascular supply to the vaginal wall (Nelissen and White, 2012). Furthermore, incontinence is possible when the neurovascular supply to the bladder, urethra and/ or rectum is compromised by not carefully dissecting the vagina (Salomon et al., 2004). Other possible postoperative complications include bacterial infection, perineal swelling, irritation of the episiotomy incision, bleeding, dysuria, stranguria, pollakisuria, hematuria and perineal hernia formation (Viehoff and Sjollema, 2003;Salomon et al., 2004;Connery and Spotswood, 2012).
Although vaginectomy involves infrequently performed invasive surgery for a mostly benign process, intra-and postoperative complications seem rare (Viehoff and Sjollema, 2003;Salomon et al., 2004;Connery and Spotswood, 2012;Nelissen and White, 2012). The surgical technique combining a laparotomy and episiotomy approach yields a favorable outcome (Nelissen and White, 2012). However, while performing the vaginectomy technique on the dogs of the present study, the question arose whether more severe complications due to the rough nature of the procedure through the episiotomy site are to be expected. The goal of this study was therefore to visualize the intrapelvic course of the blood vessels supplying the vaginal wall and to evaluate their state during (and after) the vaginectomy procedure.

MATERIAL AND METHODS
Five cadavers of different dog breeds, age and neuter status were used. All animals had been euthanized for reasons unrelated to this study. Latex injection with minimal vessel dissection was performed in all dogs.

Abdominal procedure
The dogs were positioned in dorsal recumbency and the abdominal cavity was opened by performing a caudal ventral midline celiotomy approach. Careful dissection and organ displacement were performed to visualize the abdominal aorta just caudal to the origin of the renal arteries. Through a small incision in the aortic wall, a feeding-tube (6F Nutrisafe Sterile Feeding Tube 10 mL Syringe, Abnoba Pet Store, Brierley Hill West Midlands, United Kingdom) was placed in the abdominal aorta just caudal to the renal arteries and secured by an encircling ligature (polydioxanone) (Figure 1). To reduce the total amount of latex needed to achieve the filling of the vascular structures of interest, both femoral arteries were ligated through a small skin incision at the location of the femoral triangle, bounded by the sartorius and pectineus muscles (Figure 1). A 20-mL syringe was used to inject an aqueous latex solution (V-Sure Eco Latex Natuurrubber, Vosschemie Benelux, Lier, Belgium) mixed with methylene blue (Methyleenblauw 25 mL, Euromex, Edegem, Belgium) as a coloring agent into the abdominal aorta. Adequate contrast was achieved by mixing 5 mL methylene blue per 100 mL latex. The total amount injected into the feeding tube was deemed sufficient when counterpressure on the 20-mL syringe plunger was felt. After curing of the latex for at least 12 hours, the celiotomy incision was enlarged until it reached from the xiphoid cartilage to the pecten of the pubic bone.
In the intact dogs of the present study, the ovarian pedicles were double ligated (polydioxanone) and transsected as during a standard ovariohysterectomy (Figure 2A). The bladder was retroflexed to gain exposure to the vagina and the surrounding vessels leading to the female genital tract (vaginal artery, internal pudendal artery, caudal vesical artery, uterine branch of the vaginal artery, etc). A double encircling ligature (polydioxanone) was placed just caudal to the cervix that was subsequently transsected cranial to those ligatures. The female genital tract was then removed ( Figure 2B).
Next, the muscles located on the ventral aspect of the ischiatic spine and pubic ramen were removed. A handsaw was used to remove an ischiopubic flap which allowed maximal intrapelvic visibility and accessibility of the female genital tract (Figure 3). Hereupon, the dogs were repositioned and placed in a perineal position in order to perform a standard total vaginectomy.

Vaginal procedure
The dogs were positioned in sternal recumbency with the hindquarters slightly elevated (Trendelenburg position) and the pelvic limbs extended caudally over the edge of the surgical table ( Figure 4A). The tail was restrained cranially in the dorsal midline and a purse string suture was placed around the anus. Doyen clamps were positioned with one blade in the vestibular lumen and the other blade on the skin surface. A midline episiotomy incision was made until visibility of the urinary papilla was achieved ( Figure  4B). As soon as the urinary papilla was visible, a urinary catheter (Foley catheter, Pediatric (2-way), 5 cc balloon, A.M. Bickford, New York, United States) was placed to highlight the papilla ( Figure 4C) as to prevent damage during surgery. Immediately cranial to the urinary papilla, a full thickness circular incision

Postvaginectomy
After the total vaginectomy, the dogs were again positioned in dorsal recumbency and intra-abdominal and intrapelvic damage to supplying blood vessels was mapped by taking pictures and comparing these to descriptions in a leading textbook of veterinary anatomy . Vessel damage was then compared to pictures taken before the vaginectomy.

RESULTS AND DISCUSSION
The size of the cadavers ranged from a small Yorkshire terrier to a large Great Dane. Other breeds used included a rough haired Teckel, a Labrador Retriever and a Boxer. Both the Great Dane and the rough haired Teckel were female and intact. The other dogs had already been ovariectomized. Age and clinical Although larger dogs are easier to be visualized, sufficient visualization of the vaginal supplying vessels could be achieved by combining a caudal laparotomy approach, ischiopubic flap removal and retroflexion of the bladder of all five dogs (Figures 4, 5 and  6). The removal of an ischiopubic flap was crucial to achieve visualization of the supplying vessels located deeply within the pelvic cavity. Visualization of the supplying blood vessels was further improved by vascular casting with latex mixed with methylene blue as a coloring agent. Curing of the latex for 12-24 hours resulted in strong and firm colored vessels. The latex solution could even reach the smallest vesical vessels. Ligation of the abdominal aorta at the height of the renal arteries and at both femoral arteries at the height of the trigonum femorale mediale (Scarpa's triangle) resulted in an adequate filling of the supplying female genital tract vessels (Figure 1).
The major blood supply of the female genital tract is derived from the vaginal artery. Other supplying vessels include the ovarian artery and the internal pudendal artery. The vaginal artery continues as the uterine branch of the vaginal artery, the median rectal artery and the caudal vesical artery .
Caudal traction on the vagina and its supplying blood vessels (vaginal artery, caudal vesical artery, uterine branch of the vaginal artery, etc.) via the episiotomy site resulted in ruptured vessels at the abdominal site. In particular the caudal vesical artery and the  (Figure 7). The vessel damage consistently occurred in all cadavers when following the adapted vaginectomy procedure via episiotomy (Nelissen and White, 2012). Although neutered, female dogs had a less prominent genital tract vascularization, vessel damage to the caudal vesical artery and the uterine branch of the vaginal artery was comparable to that found in intact, female dogs. Despite ample documentation that vaginectomy only rarely results in intra-and postoperative complications (Kyles et al., 1996;Gower et al., 2008;Nelissen and White, 2012;Alonge et al., 2015;Igna et al., 2016), it stands to reason how this is possible.
In the post-mortem study, both the uterine branch of the vaginal artery and the caudal vesical artery were demonstrated to rupture during the episiotomy approach of the vaginectomy procedure (Figure 7). After damage, the affected vessel will spasm, a platelet plug will be formed, the complex cascade of coagulation will be activated, and a fibrin plug will be formed (LaPelusa and Dave, 2019). These consecutive steps efficiently stop blood loss whenever small vessels are damaged but trauma to those decently sized vessels should normally result in extensive intra-abdominal and -pelvic bleeding. These vessels cannot be reached for ligation during the laparotomy approach due to their localization deeply within the pelvis .

A B C
During surgery, it is common to use an electrocautery device to control intraoperative bleeding during the episiotomy part of the surgery (Nelissen and White, 2012). However, it seems unlikely that the uterine branch of the vaginal artery and the caudal vesical artery can be reached with the electrocautery device during the vaginectomy via episiotomy. Rupture of the caudal vesical artery may also lead to insufficient perfusion of the bladder since the cranial vesical artery is often rudimentary or not present in dogs . It therefore remains to be elucidated why these theoretical major postoperative complications do not seem to occur in dogs treated by vaginectomy in clinical practice.