Whether standard regional lymphadenectomy can be performed is an important factor affecting the prognosis of patients with penile cancer. It is general believed that patients with staging/grades exceeding T1/G2 should undergo preventive inguinal lymphadenectomy. Some studies suggest that dynamic sentinel node biopsy (DSNB) should be performed first, and patients with positive results then undergo lymphadenectomy [7]. However, the operation of DSNB is complicated and it is difficult to carry out routinely in China. No matter what kind of incision is used in open inguinal lymphadenectomy, there is a higher chance of complications such as flap necrosis and incision infection [8, 9]. Since 2003, some studies have reported the use of VEIL, and this technique is considered safe and effective [10–12]. We carried out video endoscopic inguinal lymphadenectomy since 2013, and analyzed the results of the surgery. It does have the advantages of reducing the incidence of flap necrosis, reducing the infection rate of the incision, and speeding up the postoperative recovery. However, we found some shortcomings. We observed that patients may have subcutaneous emphysema, hypercapnia and other complications during and after surgery. In particular, we have observed local skin metastases in two patients underwent VEIL. Analyzing the reasons may be related to the use of conventional carbon dioxide gas pressure (12–15 mmHg) during the surgery. In previous studies of VEIL, the intraoperative CO2 pressure is usually maintained at 12–15 mmHg [13, 14], which is usually used in laparoscopy. Since October 2015, we have improved the technology of VEIL, using low pressure (5–7 mmHg) during surgery, and the operation results are good. Because of the anatomical characteristics of the groin area, the local tissue is loose, and the broad fascia extends upwards above the inguinal ligament and extends to the external oblique tendon and extends inward and outward to the perineal fascia and gluteal fascia, respectively. Carbon dioxide under high pressure can easily diffuse through these loose spaces, especially the abdomen and scrotum, and be absorbed to form different degrees of subcutaneous emphysema, which may cause complications such as elevated airway pressure and hypercapnia. Pahwa reported 10/10 cases of subcutaneous emphysema after VEIL [15]. Delman reported in 32 patients underwent VEIL, three patients experienced elevated end-expiratory CO2 partial pressure, and one patient was converted to open surgery for this reason. Six patients developed cellulitis after surgery [16]. We reduced the intraoperative carbon dioxide pressure to about 5 mmHg and found that the intraoperative space and visual field did not become restricted. The difficulty and duration of operation did not increase.
In this study, all surgeries are performed by two experienced surgeons. Since the intraoperative carbon dioxide pressure reduction did not increase the difficulty of the operation, the operation duration was not prolonged. In terms of surgical results, no matter the amount intraoperative of bleeding, the number of lymph nodes cleaned or the drainage after the operation, there was no statistical difference between the two groups. We found that in the LP group, the effect of carbon dioxide accumulation during surgery on the body was significantly smaller. It can be seen from the pH value, partial pressure of carbon dioxide, be value and other indexes in the blood gas analysis at the end of operation that the influence of carbon dioxide accumulation in NP group is more significant. Nearly half of the patients in the NP group (9/19) developed varying degrees of subcutaneous emphysema after surgery, which is rare in the LP group (2/25). More importantly, we observed 2 patients with skin metastasis after VEIL in the NP group and 1 patients with lung metastasis, but not in the LP group. Skin implant metastasis has also been reported in other VEIL studies [17].The appearance of skin metastasis is scattered nodules in the scope of cleaning. We consider that there may be a relationship between high intraoperative carbon dioxide pressure and skin implant metastasis as well as hematogenous metastasis. Reducing the intraoperative carbon dioxide pressure is not only beneficial for reducing the chance of postoperative complications, but also for tumor control.
Studies have shown that seven or more lymph nodes removed each side, or 15 lymph nodes removed bilaterally can be considered a reliable threshold [18, 19]. Regardless of the LP group or the NP group, the number of lymph nodes removed during the operation averaged more than 10 each side, which could achieve the purpose of preventive lymphadenectomy. All the patients in the two groups had incisions healed after the operation without flap necrosis and incision splitting, which was the biggest advantage of VEIL. Only a small number of patients have postoperative lymphocystis or lymphangitis, which can be cured after simple treatment. These minor complications do not affect the length of postoperative hospital stay.
When setting up the operating space, it is difficult to reach the accurate layer for operation with a finger through a small incision through blunt separation, especially in areas that cannot be seen directly. If the operation layer is completely separated under direct vision, the skin incision will be larger. First, we to use fingers to bluntly separate operating space in the area below the cleaning range though a small incision. If this space is exactly at the right layer is the best. If not, we can use the ultrasonic knife to find the accurate level from the bottom of the cleaning range and then start the operation. Such procedure can make the incision smaller and not take much time in the early stage of the surgery.
This study is not a prospective randomized controlled study and the patients in the NP group were all retrospective data, so there are inevitable biases in the choice of patients. The surgeries of the two groups were not in the same period. When completing surgeries for LP group patients, the surgeons' technical proficiency in VEIL may be better, which may cause bias in the final result. The total number of patients was relatively small, and some patients were lost to follow-up after a period after surgery. Therefore, the reliable results of long-term recurrence rate and survival rate cannot be obtained. Only the statistics of recurrence and death cases were listed.