Anatomical Study On The Middle Rectal Artery And Its Related Structures

[Background]The middle rectal rectum is one of the main three arteries in the rectum vascular supplying system. In Chinese literature, the dissection terminology for the vessel should be translated as "Inferior rectal artery" word by word in Chinese. The differences between the Chinese and English terminology for the vessel finally lead to incorrect clinical practice and have side effect on the patients treated. In the related rectum surgical operation, surgeon's extensive worries on the middle rectal artery will eventually affect the surgery treatment result. In fact, regarding the dispute on the middle rectal artery, the naming is not the only cause. Until 1983, "middle rectal artery" wad first accepted officially by Nomina Anatomica published by the International Anatomical Nomenclature Committee(IANC). The primary cause, both the domestic and foreign anatomist thought that there was great variability about the artery on itself, and the vessel had long been considered as an inconstant vessel. This huge variability manifested in the following aspects:the information got from literatures about the frequency of the occurrence of the blood vessel differs from one to one, such as, "very little" in one but the others may said there was 100%; the origin variation is very big; sometimes the vessel was found as one-side pelvis existence, sometimes was found at both sides of the pelvis. Therefore, lots of the scholars thought the middle rectal artery as one unimportant blood vessel. In fact, around the middle rectal artey, there are many unsolved mysteries.1, rectal lateral ligament was found in the original autopsy was considered to be the rectum artery vascular sheath. But the nowadays' clinical view is that in surgery procedure, the cut rectal lateral ligaments do not need to be ligated.. Why is this? 2, It is generally accepted that lateral lymph node metastasis of colorectal cancer was happened along the middle rectal artery. But how it happens about the relationship between situation and the anatomic findings about the vessel? 3, The total mesorectum exisition(TME) is now regarded as the standard operation for the rectal cancer. However, there is no literature discussing whether the middle rectal artery runs into the mesorectum, and what kind of impact does the rectal surgery itself has on the vessel. Therefore, we hope that some anatomical discoveries will provide some clues for the solving for these questions.[Objective]This study aims to discover the distribution characteristics of the middle rectal artery in the pelvis, observe the relationship between the rectal lateral ligament and the vessel, and relationship between the mesorectum and the middle rectal artery, and finally provide anatomic evidence for the operation procedure.[Method]From September 2008 to September 2009,20 voluntary contributions adult corpse collected by the Second Military Medical University Red Cross,15 males and 5 females, were provided by the department of anatomy teaching and research, Second Military Medical University. All specimens were treated with red latex through the whole arterial perfusion, then embalmed in 4%formaldehyde solution. Research specimens drawn: cross-sectional body was taken on the plane from the fourth lumbar vertebra and down to upper 1/3 part of the thigh, keeping the pelvic complete. From the upper edge of pubic symphysis, inguinal ligament, iliac muscle, anterior abdominal resection was applied and the small intestine, sigmoid colon and above was removed. After that, the basin and the intestine contents was cleared. Mobilization of the posterior and anterior aspect of the rectum was taken in strict accordance with the requirements of the total mesorectum excision.After the mobilization was finished, observe the relationship between the rectal lateral ligament and pelvic wall. At the area where the ureter run into the pelvic, umbilical artery cord was identified. Then along upper edge of the umbilical artery cord, the peritoneum was dissected, and para-bladder space was exposed. Pull the ureter medial to the pelvis, expose vesicohypogastric fascia, which located just between the n the rectum and pelvic parietal wall, and observe its morphological distribution; dissection was taken along the merging area between the vesicohypogastric fascia and the parietal fascia, with the integration of visceral-parietal fascia cut, revealing the visceral branch trunk of the internal iliac artery till to the pelvic floor where the pudendal artery piercing the pelvic diaphragm. Identify the iliac artery branches in the vesicohypogastric fascia and follow the arteries into the rectum. The vessels ending at the rectum was regarded as the middle rectal artery. The basic situation of the middle rectal artery was recorded:vessel's origin, the vessel diameter at the origin, the vessel diameter at the termination, vessel length and vessel distribution, and the relationships between the middle rectal artery and the fasciae.[Result]10 specimens were excluded for the reasons of pelvic organ dissection(3), pelvic deformity(1) and latex perfusion failure(6). Study Using pelvis specimen were 10, males 7 and females 3. A total of 12 middle rectal artery was found in 20 half pelvis. Three specimens had the middle rectal artery on both sides, among which was male 1 and female 2.6 were unilateral, including five in the left pelvis (female 1 case, male=4), one on the right side of (a male specimens). No vessel was found in one case. The average middle rectal artery diameter at origin and termination was1.72±0.81mm and 1.63±0.78mm respectively. The average length of the middle rectal artery was 63.90±16.89mm.10 middle rectal artery originated from the interior pudendal artery,1 artery originated from the gluteal artery.2,20 vesicohypogastric fascia were found, visceral branches of internal iliac artery run into the corresponding pelvic organs through the bladder. The middle rectal artery located at the bottom of vesicohypogastric fascia.3,20 cases of rectal lateral ligament were found in 20 half pelvis. The rectal lateral ligament was formed with the pelvic splanchnic nerve, rectal branches of inferior hypogastric plexus and Denonvilliers fascia.4, there were five middle rectal arteries run into the mesorectum. Among 5 middle rectal arteries in women, there are four entering the rectum at the joint place between the pelvic diaphragm and the rectum, and each one diverged into 2-3 before piercing the rectal muscular lamina.1 vessels sent 2-3 vaginal branches before entering the rectum with the trunk entering the rectum, which directly anastomosesed with the superior rectal artery in the mesorectum. In the men's 7, there are two ateries entering the rectum at the place where the rectum pierced the pelvic diaphragm, and the other with two branches, one run into the rectum just behind the prostate gland; 3 sent 2-3 branches to the prostate before running into the rectum just behind the prostate. There were 6 middle rectal arteries entering the rectum outside the mesorectum.[Conclusion]1.MRA is a more constant present vessel for the rectal blood supply, unilateral ones are more than the bilateral ones.2.MRAs just run along the surface of the levator ani.3.Rectal artery traveling range is confined to the vesicohypogastric fascia.4.There are two contacting forms between MRA and the rectum:one is that the MRA run into the rectum at the junction of the rectum and levator ani muscle, another is that the MRA run into the mesorectum across the fasica.5. MRA was not found in the rectal lateral ligament.6. Crossing the mesorectum may be taken as the judge basis for single or middle rectal artery in pelvis.7. The MRA that did not enter the mesorectum will not be damaged during TME. 8. Lateral lymph node metastasis maybe occur along the MRA not entering the mesorectum.