Since Phillipe Mouret of France performed the first laparoscopic cholecystectomy (LC) in 1987, multiport conventional LC (CLC) has become the gold standard for the treatment of gallbladder (GB) disease [1], with advantages of better cosmesis, less scar, less pain, and shorter hospitalization [2]. Surgeons have attempted to reduce number of ports and incisions with accumulation of experience and development of equipments for the past few decades. Single incision laparoscopic cholecystectomy (SILC) was first performed by Navarra et al. [3] in 1997, but did not regain much popularity since the development. However, the recent increase in use of SILC can be attributed to new surgical techniques and equipment, such as the articulating instruments and access ports capable of allowing several instrument to be inserted in a single ports [4,5,6]. Nowadays, the 3-channel method with multiport access is commonly used in SILC [7]. Despite the new techniques and exponential improvement of equipment, there still remains some limitations, such as difficulty in exposure of the Calot's triangle, narrow indications (exclusion criteria: high body mass index [BMI], previous abdominal surgery, acute cholecystitis with severe gallbladder [GB] inflammation), and higher bile duct injury rate with the 3-channel SILC [8,9]. For these reasons, adequacy and feasibility of SILC is still controversial. Previously, we had also performed 3-channel SILC with 2 instruments and a flexible telescope, but encountered similar limitations. Therefore, we have replaced our standard setting into a 4-channel SILC with an addition of a snake retractor for resolution of the aforementioned limitations. In this study, we hereby report an adequacy and feasibility of 4-channel single incision laparoscopic cholecystectomy using a snake retractor.

We have conducted retrospective review of 415 patients that underwent SILC between April 2010 and February 2013. From April 2010 through September 2012, 326 patients had been treated with 3-channel method using a handmade single port, a flexible telescope and two articulating instruments. In the early period, we excluded those who were older than 70 years of age with radiologic or pulmonologic comorbidities, or acute GB inflammation, but did not exclude patients with high BMI or history of abdominal surgery. After 50 cases, with accumulation of experience, the inclusion criteria of SILC was expanded to all the patients who would typically be considered for CLC, but excluded the patients with suspected early-staged GB malignancy [10]. After October 2012, we have modified our 3-channel method to a 4-channel SILC by adding a snake retractor for liver retraction which we later named as "modified Konyang standard method". Eighty-nine patients have been treated with the 4-channel SILC using a snake retractor, and the inclusion criteria for the 4-channel SILC had been applied equally.

Since Phillipe Mouret of France performed the first LC in 1987 [1], the superiority of LC as the standard procedure for GB removal compared to the open cholecystectomy has not been questioned due to better cosmetic satisfaction, less scar, less pain, and shorter hospitalization [2]. Ever since the initial development of LC, surgeons had attempted to reduce the number and the size of ports. In these efforts, more challenging and innovative methods like natural orifice transluminal endoscopic surgery (NOTES) have been invented and developed. Since the first NOTES transvaginal cholecystectomy by Bessler et al. [11] of the United States in 2007, numerous NOTES cholecystectomies have been performed. However, some challenges still exist, including longer operating time, poor triangulation of instruments, difficulty in standardization of the procedure, and increased risks of leakage and fistula, which clearly indicates that improvement of the NOTES surgical techniques and instruments is much needed [7,11]. Nowadays, surgeons have switched their focus to single incision laparoscopic surgery as an alternative minimally invasive surgery to the NOTES. Since the first SILC by Navarra et al. [3] in 1997, various new techniques and instruments have been introduced and modified. SILC has become more popular, and several studies including review of over hundred cases or meta-analysis of the operative data have been reported [12,13,14,15,16]. The SILC certainly has superior cosmetic outcome compared to the CLC. However, a surgeon should not choose SILC solely based on superior cosmesis, patient' safety still remains as a major concern. Joseph et al. [8] reported that the bile duct injury rate in SILC (0.72%) was higher than CLC (0.2%). Trastulli et al. [16] reported a meta-analysis data including 13 randomized controlled trial studies comparing SILC vs. CLC, the failure rate was 8.4% vs. 0.7%, conversion rate to open was 0.2% vs. 0.2%, overall complication rate was 7.3% vs. 6.6% and a bile leakage rate was 0.4% vs. 0.7%. Sajid et al. [13] reported postoperative pain and complications, the hospital length of stay, cosmesis score, conversion rate, and ports addition rate were statistically similar between SILC and CLC in their meta-analysis study. Although there were various studies on SILC, the inconsistencies of results among studies ranged too wide to be certain of the safety in SILC. As we mentioned earlier, a major problem when comparing CLC and SILC is the difficulty in exposure of the Calot's triangle. Aprea et al. [17], Cao et al. [18], Edwards et al. [19], etc., many surgeons have used percutaneous anchorage with sutures and Lirici et al. [20] used needlescopic grasper for GB retraction and reducing complications. The most difficult problems of the 3-channel SILC in our department were similar to those reported from other institutes, which were inadequate visualization of the Calot's triangle and clash between the instruments and the telescope. In order to resolve these issues, we used a flexible telescope and articulating long instruments, and standardized our method, which was to retract the GB inferolaterally by right hand and to dissect the cystic duct and artery by left hand while positioning the flexible telescope at the left side of the working instruments [21]. Despite the standardization of our method, visualization of the Calot's triangle was still incomplete, especially when the GB was acutely inflamed. Thus, we incorporated a snake tractor to address the remaining issue. We had initially proposed that our modified 4-channel SILC wound have certain benefits, such as for better exposure of the Calot's triangle, and decrease in ports addition, conversion rate, and complication rate. We performed SILC in a selected patient population without severe comorbidities, or acute cholecystitis in the early period in the formerly published studies [8,22,23], but we expanded indications for SILC while increasing the number of the SILC cases, and performed 3- and 4-channel SILC on patients with major comorbidities, obesity, previous abdominal surgery, and acute cholecystitis pretreated with PTGBD, but excluded patients with possible early stage GB malignancy. A proportion of patients with acute cholecystitis, who treated with PTGBD before an operation, was 30 (9.2%) in 3-channel SILC and 23 (25.8%) in 4-channel SILC. This raises a possibility that the 4-channel SILC could be applicable for more patients with acute cholecystitis. There were total 9 cases of CLC conversion including 6 cases in the 3-channel SILC group and 3 cases in the 4-channel SILC group, due to the cystic artery bleeding. We recommended reducing this problem by ligating the cystic artery before the cystic duct ligation. There was only single wound infection case in the 4-channel SILC group and no major complication like the bile duct injury. However, there were some limitations in our study. One is the small sample size, and the other is a lower conversion and complication rate compared to other studies [13]. The latter is most likely due to the amount of experience by the surgeon who performed the 4-channel SILC, since he had previously performed over 2,000 cases of the CLC. Surely, we need larger sized samples and long-term follow-up studies. But we considered that the 4-channel SILC can become one of the primary treatments of benign GB disease in the future.

In conclusion, 4-channel single incision laparoscopic cholecystectomy has certain advantages such as better visibility and accessibility for dissection of the Calot's triangle, and reproducible methods in experienced hands. 4-channel SILC is deemed safe and feasible; therefore, most benign diseases of GB could be treated with the 4-channel SILC using a snake retractor.