A comprehensive and in-depth understanding of the pelvic anatomy is the basis for the smooth performance of rectal surgery. For a long time, scholars have done a lot of research work on the anterior and posterior fascial structures of the rectum and their connections, but the elaboration of the lateral fascial structures of the rectum and their relationships is limited in the literature so far. Foreign scholars have proposed the concept of vesicohypogastric fascia (VHGF) for the lateral rectal fascia [1] and considered its lowermost boundary as the “inferior rectal artery”, but the description of its morphology and its interrelationship is not clear, which brings confusion to clinicians for smooth rectal surgery. However, their morphology and interrelationship are not clearly described, which brings confusion to clinicians for smooth rectal surgery. In this study, the morphological structure and relationship of the inferior ventral fascia of the lateral rectal bladder and its related clinical significance were initially investigated, aiming to provide a morphological reference for clinical rectal surgery to reduce injuries and complications.
1. Materials and methods (1) Study materials The cadaveric specimens were obtained from 10 voluntarily donated adult cadavers collected by the Red Cross Society of the Second Military Medical University and provided by the Department of Anatomy and Research of the Second Military Medical University between September 2008 and September 2009. Seven of them were male and three were female, with a mean age of (66.80±11.09) years.
Apparatus and equipment Data were measured with SF2000 electronic digital calipers (produced by Guilin Guanglu Digital Measurement and Control Co., Ltd.), and photographic data were collected by shooting with a Nikon E8800 digital camera.
(2) Methods Cadaver preparation The right femoral artery was cannulated, and the red latex solution was instilled from the femoral artery at a pressure of 3 to 3.5 kg/cm2 , and the superficial temporal artery was observed to be well filled. The pressure was maintained for 10 min to allow better filling of the artery. The perfused cadaver was immersed in 10% formalin solution for fixation.
Specimen sampling The pelvic specimens were taken from the 4th lumbar plane up to the upper 1/3 of the thigh transecting the cadaver. The anterior abdominal wall was excised from the superior border of the pubic symphysis, inguinal ligament, and iliac crest, the small intestine and colon above the sigmoid colon were removed, and the pelvic cavity was cleansed to remove intestinal contents.
Exposure of the subperitoneal fascia of the bladder Free the rectum: lift the sigmoid colon and pull it to the right side, cut along the peritoneal reflex at the left root of the sigmoid mesentery and extend it down to the rectal bladder trap (rectal uterine trap for women). The peritoneum of the pelvic wall was separated to the left to reveal the left ureter. The sigmoid mesentery is freed to the right to the bifurcation of the abdominal aorta, then the sigmoid colon is turned to the left and the right root of the sigmoid colon is incised and separated upward to the root of the inferior mesenteric artery and downward to the rectal bladder sulcus (or rectal uterine sulcus) to join the contralateral side. The lateral peritoneum of the rectum was incised, the sigmoid colon and its mesentery were lifted, and the peritoneum on both sides of the rectum was incised medially in the ureter to the anterior rectal recess of the uterus or the rectal recess of the bladder, which was retracted toward the bladder to fully expose the anterior sacral hiatus posterior to the rectum, and the lax tissue within the anterior sacral hiatus was sharply separated with a scalpel to reach the sacral rectal ligament. The anterior lobe of the pelvic floor at the lowest point of the peritoneal cut is clamped up with a vascular clamp, while the anterior bladder or uterovagina is pulled forward and upward with a deep pulling hook to reveal the tougher Denonvilliers fascia, and the freeing continues anterior to this fascia to reach the seminal vesicles and prostate. If there is difficulty in exposure, the anterior pubic symphysis can be clamped away to expose the posterior pubic space, and the anterior rectal organs can be dissected in a median sagittal position.
Exposing the subabdominal fascia of the bladder: at the point where the ureter enters the pelvis, the umbilical artery cord is identified, and the lateral space between the lateral wall of the pelvis and the bladder is entered by cutting the peritoneum with its upper edge. After holding the ureter toward the medial side of the pelvis, a lamellar structure continuous with the sacrum and bladder is seen between the rectum and the pelvic wall, which is the subperitoneal fascia of the bladder.
(3) Observations The location of the subperitoneal fascia of the bladder, its morphological structure and its relationship with the rectum were observed.
(2) Results (1) Location of the subdominal fascia of the bladder The subdominal fascia of the bladder is located on both sides of the pelvis. When viewed from the medial side of the pelvis, the dorsal rectal fascia tissue was seen to continue with the intrapelvic fascia portion of this interfold tissue. In the direction of the lateral bladder gap, this subperitoneal fascia of the bladder continues with the visceral fascia of the bladder towards the lateral pelvic wall, thus making the subperitoneal fascia of the bladder a transitional structure between the bladder and the internal iliac vessel sheath. A clear migration can be seen between the inferior ventral fascia of the bladder and the superior pelvic diaphragm fascia that covers the surface of the anal raphe. The left and right sides of the subdominal fascia of the bladder are similarly positioned in the pelvis.
(2) Morphologic structure of the inferior ventral fascia of the bladder After complete exposure of the lateral bladder space, the superior, posterior, and inferior edges of the inferior ventral fascia of the bladder can be identified. The upper posterior margin begins at the point where the umbilical artery branches from the internal iliac artery and goes down to the point equivalent to the internal pubic artery exiting the pelvis. The beginning of the inferior margin coincides with the end of the posterior margin and continues anteriorly to the bladder inferior to the arch of the anal raphe tendon.
The fascias of the pelvic wall and visceral transposition are incised to expose the trunk of the visceral branch of the internal iliac artery and the beginning of the corresponding visceral branch artery to the internal pubic artery exiting the pelvic diaphragm. By tracing the beginning of each visceral branch artery, the superior cystic artery (or uterine artery in women), the inferior cystic artery, and the inferior rectal artery can be isolated one by one. The fascial structures attached to the ureter as it enters the pelvis are also involved in the composition of the subperitoneal fascia of the bladder. The vas deferens is seen hidden within the continuous portion of the medial pelvic fascia of the inferior ventral fascia of the bladder toward the bladder.
(3) Relationship between the subdominal fascia of the bladder and the rectum The connections and boundaries between the lateral layer of the subdominal fascia of the bladder in the lateral bladder space and the fascia of the pelvic wall are relatively clear and the anatomical relationships are relatively fixed. However, in the medial pelvic cavity, the relationship between the medial layer of the subdominal fascia of the bladder and the pelvic organs is not as fixed as that with the pelvic wall fascia, but it is not as fluid as one might expect. The inferior ventral fascia of the bladder continues with the posterior rectus fascia, and this connection is most evident and strongest in the plane corresponding to sacral 3. The plane of migration of the inferior ventral fascia of the bladder to the surface fascia of the rectum is the same as that of its migration to the pelvic organs and wall fascia. Posterior to the prostate or vagina and anterior to the intrinsic rectal fascia, the subdominal fascia of the bladder and Denonvilliers fascia migrate with each other.
The medial layer of the inferior ventral fascia of the bladder and the Denonvilliers fascia form the ventral aspect of the lateral rectal ligament below the retroperitoneum.
3, Discussion Intrapelvic fascial structures are divided into pelvic visceral fascia and pelvic wall fascia according to their distribution in the pelvic organs and walls. The fascial structures surrounding the rectum, bladder, neurovascular, etc. are the pelvic visceral fascia; the fascial structures attached to the surface of the medial occlusal muscle, anal raphe, and pear-shaped muscle to close the entire pelvic floor form the pelvic wall fascia. Therefore, the subperitoneal fascia of the bladder belongs to the pelvic visceral fascia in principle.
(1) Origin of the inferior ventral fascia of the bladder The inferior ventral fascia of the bladder is a translation of the French word (aponévrose ombilico-prévésicale). It is named after the internal iliac vessels (which were once called the hapogastric vessles), the hapogastric nerves, and the ureters. In 20 lateral pelvic specimens, the author observed that the internal iliac artery extended ventrally, dividing into the occluding artery and the visceral branch arteries. The subperitoneal fascia of the bladder is a fascial structure covering the surface of the visceral branch arteries below the cord of the umbilical artery, and its position in the pelvis is exactly between the pelvic wall and the intrapelvic organs.
(2) Structural characteristics of the inferior ventral fascia of the bladder From the anatomical observations in this paper, the inferior ventral fascia of the bladder is in a sagittal position in the pelvic cavity and is composed of a double layer of visceral fascia of the rectum and pars recti. It is narrow superiorly and wide inferiorly, and the umbilical artery is the definite superior edge of the subperitoneal fascia of the bladder. The vessels of the visceral branches of the internal iliac artery are located within the subperitoneal fascia of the bladder. If the ureter is the boundary, the umbilical and superior cystic arteries are above it, and below it are the inferior cystic and inferior rectal arteries. Below the ureter the fascial tissue is markedly thickened and the contents are increased. In foreign literature, this is referred to as the vascular nerve bundle, but the “bundle” ignores the orderly arrangement of intrafascial structures. It is also called the “inferior ureteral fascia”, but this terminology severed the natural structure from the umbilical artery down. Therefore, it seems more appropriate to consider this fascial structure as a whole.
(3) Relationship between the inferior ventral fascia of the bladder and the pelvic organs and wall fascia The lateral layer of the inferior ventral fascia of the bladder is morphologically well represented by the migrating fusion between the pelvic organs and wall fascia. From the results of this paper, it can be found that the subdominal fascia of the bladder has distinct boundaries. The upper boundary is the umbilical artery, and the lower boundary is the fascial arch formed by the migration between the pelvic wall fascia and the superior pelvic diaphragm fascia, which is a thickened part of the superior pelvic diaphragm fascia, rather than the anal raphe tendon arch as suggested by Lin et al. The posterior border of the inferior ventral fascia of the bladder is a coronal migration between the lateral layer and the pelvic diaphragm, and anteriorly it ends at the lateral border of the posterior pubic space of the bladder. The migration of the pelvic visceral and wall fascia is fused inferiorly within the tendon arch of the levator aponeurosis. The medial layer of the inferior ventral fascia of the bladder is continuous with the surface fascia of the rectum. Posterior to the seminal vesicles, the medial layers of the subdominal fascia of the bladder on both sides interconnect in the median line to become Denonvilliers fascia.
(4) The relationship between the inferior ventral fascia of the bladder and the lateral rectal ligament The lateral rectal ligament is a structure that becomes visible after the anterior and posterior freeing of the rectum is completed. The anterior freeing of the rectum is performed anterior to the Denonvilliers fascia, and from the anatomy of this study, no severance or other treatment of the Denonvilliers fascia was performed during this process, at which point the Denonvilliers fascia became the main fascia anterior to the lateral rectal ligament. We believe that the lateral rectal ligament is formed by connective tissue and vascular nerves, and is a continuation of the subabdominal fascia of the bladder to the Denonvilliers fascia anterior to the rectal mesentery, a fascial-neural complex structure formed by a connective tissue matrix with the participation of pelvic nerve fibers. Among these nerve fibers, the rectal branch of the inferior ventral plexus is predominant, and some of the pelvic visceral nerve fibers can be found joined.
(5) Relationship between the inferior ventral fascia of the bladder and the inferior rectal artery The inferior rectal artery is located immediately on the surface of the anal raphe, at the lowermost part of the inferior ventral fascia of the bladder. According to the distribution characteristics of the inferior rectal artery, the injury to the inferior rectal artery can be completely avoided when freeing the middle and lower rectum during rectal cancer surgery to ensure the blood supply to the rectal stump.
(6) Relationship between the inferior ventral fascia of the bladder and the pelvic plexus From the observation of this paper, we can see that the pelvic plexus is located below the inferior ventral fascia of the bladder, immediately outside the inner layer of the inferior ventral fascia of the bladder. Avoiding pelvic plexus injury is one of the keys to reducing postoperative complications when performing intermediate and low rectal surgery. In the coronal view of the pelvis, there is a clear boundary between the fascia where the pelvic plexus is located and the rectum.
The intrapelvic fascial structures should be considered as a whole, and there is a natural migration between the pelvic viscera and wall fascia. The subperitoneal fascia of the bladder is an important fascial structure lateral to the rectum, and an in-depth understanding of it can help to enhance the understanding of the adjacent anatomic relationship between important intrapelvic vessels and nerves and the rectum, which can avoid or reduce the complications of rectal surgery.