4.1 Results in the Context of Published Literature
Although chylous leak is a rare complication in gynecologic malignancies, its incidence has increased with more aggressive retroperitoneal surgery, especially laparoscopic surgery in recent years .In our study, preoperative anemia and enlarged lymph nodes were risk factors for chylous leakage in a univariate analysis, whereas preoperative anemia was the only risk factor in a multivariate analysis. Some of the literature reached similar conclusions to ours.Li et al.[8] found that neoadjuvant chemotherapy, postoperative anemia, and postoperative hypoproteinemia are risk factors for postoperative lymph leakage[8]. Varghese et al. [9] conducted a meta-analysis undergoing pancreatic surgery and found that younger age, low prognostic nutritional index, para-aortic node manipulation, lymphatic involvement, and post-pancreatectomy pancreatitis are risk factors for the development of chylous leak; this result is similar to our findings.[9] In a retrospective analysis of 234 patients undergoing laparoscopic retroperitoneal lymphadenectomy for gynecological cancer, Kong et al. [10]found that lymphatic ascites are not associated with the level of para-aortic lymphadenectomy but with certain underlying diseases, including cirrhosis and heart failure.[10]
Although we failed to prove that the occurrence of chylous leakage is related to enlarged lymph nodes or to the number of lymph node excision and metastasis, other studies have done so. Zhaoet et al. [6]showed that patient age, intraoperative blood loss, number of lymph nodes removed, and lymph node metastasis are not risk factors for chylous ascites after laparoscopic surgery. However, they suggested that chylous ascites is more likely to occur after laparoscopic para-aortic lymphadenectomy than after pelvic lymphadenectomy.[6] Solmaz et al.[7]. Found that the number of para-aortic lymph nodes removed is significantly greater in patients with chylous ascites.[7] Tulunayn et al. [11] concluded that injury to lymphatic vessels or cisterna chyli caused by para-aortic lymphadenectomy is the main cause of postoperative chylous ascites.[11] Han et al.[12] concluded the same by analyzing 4119 patients with gynecological malignant tumor and undergoing surgical treatment.[12] Lee et al.[13] conducted retrospective statistics on 2917 cases of primary colorectal cancer and found that the time of operation and the number of lymph nodes removed are independent risk factors for postoperative chylous ascites.[13]
The beginning of the thoracic duct, a cystic bulge called the cisterna chyli, is located in front of the T12-L1 vertebral body and behind the inferior vena cava. It is formed by the confluence of the left and right lumbar trunk and intestinal trunk and is covered by the right foot of the diaphragm. However, an anatomical variation exists in the general population. In 50% of people, the cisterna chyli is absent and is instead replaced by a lymphatic network around the abdominal aorta.[14] Because of the anatomical variation of the lymphatic system, the cisterna chyli cannot be clearly identified during retroperitoneal operation, and unconscious damage to the lymphatic vessels, particularly the cisterna chyli, may result in postoperative chylous leakage. During abdominal lymph node dissection, mesenteric root dissection, and superior mesenteric lymph node dissection, chylous ascites or chylous leakage can easily form if the distal (deep) lymphatic output tube is not ligated. During the operation, we should be familiar with the anatomical location of the lymphatic vessels and cisterna chyli. The lymphatic circulation is rich and often have variable pathways. We should pay attention to avoid damaging the lymphatic vessels and cisterna chyli.
Kim et al.[15] analyzed 622 cases of laparoscopic nephrectomy and concluded that laparoscopic surgery is more prone to chylous ascites than open surgery and that it is related to the use of single, bipolar, or ultrasonic scalpels in laparoscopic lymphadenectomy.[15] However, other studies have come to the opposite conclusion. Augustinus et al.[16]retrospectively analyzed 2159 post-pancreaticoduodenectomy patients and identified vascular resection and open surgery as risk factors for chylous leakage.[16]
Our study found that the length and cost of hospitalization in the chylous leak group were much longer than those in the control group. The occurrence of postoperative chylous leakage prolongs hospital stay, delays postoperative adjuvant therapy for malignant tumor patients, increases hospital costs, and can even lead to patient death.[17]
In our study, all 19 patients were successfully treated conservatively without any operation, which is consistent with the conclusions reported in previous studies. Most chylous leakage can be successfully treated conservatively with a regimen consisting mainly of fasting, extended drainage, total parenteral nutrition, somatostatin analogues, or a combination of these.[18] Ng et al.[19] conducted a meta-analysis of patients with colorectal malignancies who underwent surgical treatment and found that most chylous ascites cases were successfully treated with conservative treatment, whereas only three cases required surgical treatment after conservative treatment failed and were successful.[19] Scaletta et al.[20] conducted statistics and found that out of 546 patients who underwent surgery for ovarian cancer, 8 developed chylous ascites after surgery. All patients were successfully treated conservatively.[20]
For patients who fail conservative treatment, surgery and interventional therapy can be used. A number of reports have indicated that lymphangiographic embolization can successfully locate the leakage point in the treatment of chylous fistula, and the cure rate is high. Lymphadenography can be performed to further identify the cause of the disease, and radionuclide imaging can be used to understand the lymphatic fluid transport and obstruction site and thus provide a basis for further surgical treatment.[21] Previous studies showed that for the surgical treatment of chylous leakage, a number of methods can be used to find the leakage quickly and improve the success rate of surgery, including preoperative oral administration of peanut oil and other edible oils followed by laparoscopic exploration, intraoperative injection of methylene blue into the lymph nodes, intraoperative injection of indocyanine green combined with fluorescent laparoscopic navigation, and the use of a carbon nanoparticle suspension to locate chylous leakage.[22–25] The use of oral oil prior to laparoscopic para-aortic lymphadenectomy is also a feasible and effective method of showing para-aortic lymph nodes and prevent chylous leakage during operation.[26, 27] In addition to the aforementioned treatment methods, local adhesives have been reported to be effective in controlling chylous leakage.[28] Zhou et al.[29] demonstrated that Pseudomonas aeruginosa injection has a clear effect on the control of lymphatic leakage and chylous leakage in gynecological tumors.[29]
4.2 Strengths and Weaknesses
To date, this is the largest series to report the risk factors and impact of chylous leak after laparoscopic surgery for gynecological malignancies. However, the study has a number of limitations. First, because this is a retrospective analysis, and the results may be prone to selection and information biases. Second, the chylous test of leakage in this study was qualitative rather than quantitative. Thus, there may be a number of false positives. Third,not all patients in control group have a postoperative drainage tube placed, we cannot exclude that patients in the control group without postoperative drainage did not have a sub-clinical chyle leak. Multicenter, large-scale prospective studies are needed to extend our observations.