Physiological anatomy characteristics of the ‘Holy plane’ of rectal surgery and its clinical significance JIN Zhi-ming*, ZHENG Qi, XUE Li-jun,et al. Department of General Surgery, Shanghai Sixth People’s Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai 200233, China Corresponding author: YIN Lu, E-mail: yindalu@yahoo.com.cn Abstract Objective To define range of the“Holy plane”of rectal surgery, and to study its physiological anatomy characteristics and clinical significance. Methods Pelvises of 21 cadavers were all cut into two half pelvises through the median sagittal plane, thus 42 half pelvises specimens were studied by topographic dissection. All half pelvises were dissected according to a certain steps. The range of “Holy plane” was defined and measured. Rectosacral fasciae were taken and examined by immunohistochemistry, and the nerves and lymph nodes were checked. Results The “Holy plane” is between the mesorectum and the rectosacral fascia, it begins at L5-S1 and ends at pelvic fascia with fusion of the two fasciae. The lateral borders are internal iliac-vessels and lateral ligaments. Under bare eyes, the connection tissue inside the “Holy plane” is very loose and avascular. The biggest height of “Holy plane” was 16.7±1.4 cm in male pelvis and 15.4±1.2 cm in female pelvis respectively, and the biggest width of “Holy plane” was 7.2±0.6 cm in male pelvis and 6.7±0.6 cm in female pelvis respectively. There was no significant difference between them (P>0.05). Immunohistochemical results: dense nerve fibers and tiny vessels were observed in rectosacral fascia; lymphocytes could be seen occasionally, but lymph node could not be seen in it. Conclusion “Holy plane” is a symmetrical avascular anatomical space behind the rectum with a wide upper part and a narrow low part. It is a very important clue to guide the operative way and the range of clearance during rectal surgery.