Comparison of Left Lower Entrance and Traditional Laparoscopic Greater Omentum Resection for Stage I Ovarian Cancer

Objective : To describe the surgical method, safety and convenience of " lower left entrance laparoscopic greater omentum resection" and evaluate its clinical application value for stage I ovarian cancer. Methods: 31 patients with early stage I ovarian cancer underwent with laparoscopic staging surgery adopted " lower left entrance laparoscopic omentum resection " as the observation group, and 29 cases underwent by conventional laparoscopy as control group. The intraoperative and postoperative indexes were compared. Results: During the greater omentum resection, there was no signicant difference between two groups in the blood loss, but the operation time in observation group was signicantly shorter than the control group. There was no difference in postoperative hospital stay (cid:0) gastrointestinal exhaust time and postoperative severe complications. Conclusion: " lower left entrance laparoscopic greater omentum resection " may be a safe and effective technique in stage I ovarian cancer. inaccurate measurement). Intraoperative complications(the injury of stomach, intestine, liver and spleen) and postoperative severe complications (intestinal obstruction (cid:0) bacteremia (cid:0) pulmonary embolism (cid:0) Lymphocyst (cid:0) respiratory failure and deep venous thrombosis) after omentum resection, hospital stay and postoperative gastrointestinal exhaust time. All patients were followed up every 3 months. The complications and recurrence or death were observed.


Introduction
According to the NCCN guidelines, standard staging operations for early ovarian cancer (EOC) include bilateral adnexectomy hysterectomy biopsy of suspected metastatic foci peritoneal biopsy omental excision peritoneal irrigation pelvic and paraaortic lymphadenectomy [1]. Omental excision generally refers to the removal of greater omentum [2]. Studies have shown that minimally invasive surgery will not have adverse effects and affect 10-year survival [3]. Antonino Ditto et al [4]compared the feasibility and safety of stage I EOC by laparoscopy and laparotomy, the laparoscopic group had less blood loss faster recovery of defecation and shorter hospital stay but had longer operative time. Bogani et al [5] also found that the incidence of laparoscopic postoperative complications was low. However, there are some problems in the conventional laparoscopic approach, such as narrow visual eld caused by the large distance between the laparoscopy and the omentum, the surgical eld for aortic node resection which also is exposed di cultly, longer operative time. The purpose of this study is to describe the safety and reliability of laparoscopic greater omentum resection by left lower entrance in patients with stage I ovarian cancer compared with conventional laparoscopy since 2012. were selected. The rst 29 cases were treated with conventional laparoscopy(control group),next 31 cases were treated with left lower laparoscopic greater omentum resection (observation group). Case selection criteria: The patients had no severe medical diseases and can tolerate surgery. The maximum diameter of the tumor was less than 12 cm. The Ethics Committee of Chongqing Ninth People's Hospital approved the study. All patients signed informed consent.

Method
Surgical procedures followed: The ascites or lavage uid of pelvic cavity were collected for cytological examination; after high ligation of ovarian artery and vein, removal one or both adnexa were put into the specimen bag, and the rapid frozen pathology was carried out. The removal uterus was taken out from the vagina. pelvic and paraaortic lymph node were taken out from the vagina . greater omentum below transverse colon was excised. multi point peritoneal biopsy of paracolonic sulcus and pelvic wall were performed. appendectomy was performed(for mucinous tumor). The vaginal stump was sutured under laparoscope. The procedure were performed by conventional four ports ( Fig. 1-3).
We took trendelenburg position to remove the greater omentum in control group, the surgeons faced the patient's feet, the laparoscopy was inserted from A point. In the observe group, the patient's position was anti-trendelenburg. Laparoscopic holder standed on the outside of the patient's left thigh, facing the patient's head, the laparoscopy was inserted from D point towardpatient's head. The surgeon standed between patient two legs. When the greater omentum near splenic exure was resected, noninvasive forcep was put from incision A and ultrasonic scalpel was put from incision B; During the resection of the greater omentum near the liver, ultrasonic scalpel was put through incision A, and noninvasive forceps was put from the incision C (Fig. 4).

observation index
The operation time (only removal the greater omentum) intraoperative blood loss(volume change of negative pressure suction bottle during omentum resection, we did not wash to avoid inaccurate measurement). Intraoperative complications(the injury of stomach, intestine, liver and spleen) and postoperative severe complications (intestinal obstruction bacteremia pulmonary embolism Lymphocyst respiratory failure and deep venous thrombosis) after omentum resection, hospital stay and postoperative gastrointestinal exhaust time. All patients were followed up every 3 months. The complications and recurrence or death were observed.

Statistical methods
Spss17.0 statistical software (IBM Corp., New York,NY)was used,the measurement data was expressed by x̄ ± s, independent sample t test, Fisher exact test was used for counting data, and the test level was α = 0.05.

Results
2.1 Two groups general condition The age was 30-69 years old, the body mass index was 17-28.8 kg/m 2 , and the diameter was 4-12 cm; There was no signi cant difference in age, body mass index, tumor size ( Table 1). successfully completed. There were not large blood vessels. There was no signi cant difference in intraoperative blood loss between the two groups. However, the omentum resection operation time in the observe group was signi cantly shorter than that in the control group (Table 2).  (Table 3).There is no recurrence or death cases up to now. The greater omentum is a membranous tissue connecting stomach greater curvature and transverse colon [6]. The rate of peritoneal/omental metastasis in apparent early stage was 5.2% [7] Compared with traditional open surgery, laparoscopic surgery is superior to open surgery in operative vision and postoperative recovery time [8]. In epithelial ovarian cancer, minimally invasive surgery is not associated with poor survival in women with stage I disease [9]. Yoo [10] found that laparoscopic surgery did not decrease the overall survival rate and did not increase the risk of tumor cell dissemination and recurrence. In this study, there was no recurrence or death cases during the follow-up period, it it supports that laparoscopic surgery is feasible for stage I ovarian cancer.
In laparoscopic greater omental resection, because of its large coverage area, adjacent to the liver, stomach and spleen and other important organs, open and clear vision is an important. For conventional laparoscopic greater omental excision, the laparoscopy is put from the umbilical or near umbilical incision (point A) which limits vision, increasing the risk of damage surrounding organs. In order to reduce the visceral injury, ultrasonic scalpel should not be too close to transverse colon, greater curvature of stomach and splenic hilum. It is safe to remove omentum 0.5-1 cm away from normal organs surface. Although some teams used 5 ports technique for diaphragm peritoneal resection, we were used to use 4trocar technique to perform surgery by changing ports, it was also feasible.
The main complications included bleeding embolism infection myocardial infarction intestinal obstruction organ injury stula incision dehiscence, etc [11]. In control group, transverse colon serosa layer was damaged. However, the laparoscope was inserted by left lower operating hole (point D), there was enough space between the laparoscope and greater omentum,there was no organ injury in observe group, so the time in observe group was shorter than in control group. There was no signi cant difference in postoperative hospital stay and anal exhaust time between the two groups, the reasons may be: 1) there was no signi cant difference in the total operative time ; 2) it was related to postoperative chemotherapy; 3) the sample size was small. There were no serious complications in both groups, which indicated that left lower entrance for stage I ovarian cancer was safe.
To sum up, comparing with the conventional laparoscopic approach, left lower entrance can shorten the operation time. It has the characteristics of wide vision. In the future, prospective large sample and longterm further study is needed.

Declarations
Funding: This study was funded by a grant from the Shenzhen Science creation Committee( grant no.JCYJ20190809104403566).
Competing interests statement: They declares that she has no con ict of interest.  Figure 1 abdominal incisions in laparoscopic greater omental surgery The arrow shows the umbilicus. A and D were 10mm incision, B and C were 5mm. A is 3cm above the umbilicus; B and C are 0-1cm below the umbilicus. The horizontal position is 3-6cm away from the umbilicus, and D is 1/3 of the line between the left anterior superior iliac spine and the umbilicus. laparoscopic resection of splenic exure of greater omentum The red arrow was spleen