・Case history
A 64-year-old man with no medical history received a positive stool test for fecal occult blood. The patient showed no notable abnormal findings on upper gastrointestinal endoscopy. He subsequently underwent colonoscopy and was found to have a mass lesion approximately 2 cm in diameter at the lower rectum (Figure 1). Endoscopic evaluation of lesion invasion suggested infiltration into the deep submucosal layer. A biopsy revealed a histopathological diagnosis of moderately differentiated tubular adenocarcinoma. Rectal examination of the lesion showed that the lower edge of the lesion was about 3 cm away from the dentate line and had good mobility (Figure 1). No other gross lesions were noted after examining the entire large intestine. No notable abnormal findings were observed in terms of general biochemistry, complete blood count, or coagulation test. Tumor markers, including carcinoembryonic antigen and carbohydrate antigen 19-9 levels, were also within normal ranges. Computed tomography showed no clear localization of the rectal mass and no significant lymphadenopathy around the lower rectum. None of the findings suggested obvious distant metastasis. Based on the mentioned findings, we determined that surgical resection was indicated for this lesion. Furthermore, based on the positional relationship between the mass and the dentate line, we determined that ISR was appropriate and decided to perform laparoscopic ISR considering that the patient had no history of laparotomy. The patient was placed in the lithotomy position intraoperatively with his head low. We started the surgery via the transanal procedure. Accordingly, we applied the Lone Star RETRACTOR™ all around the anal canal and observed the inside of the rectum. As shown in the preoperative examination findings, the dentate line was 3 cm away from the lower edge of the mass. We dissected all layers of the rectum with a 2 cm margin from the inferior margin of the mass to the anal side. We closed the rectal stump on the resected side with a nodular suture, after which we entered the layer between the internal and external sphincters and proceeded with the detachment of the pelvic muscles to the extent that the prostate was palpable on the ventral side and the coccyx on the dorsal side. After peeling to that depth, we prepared three pieces of gauze, which was soaked in a liquid prepared by dissolving 25 mg of ICG in 10 mL of water containing sodium arginine with a concentration of 6 mg / ml, and then sufficiently squeezed out the moisture and carefully spread it all around the deepest parts so that they were in the same layer (Figure 2). Thereafter, we proceeded with laparoscopic manipulation starting with five ports. We proceeded with detachment from the inside of the sigmoid mesentery and dissected the lymph nodes around the root of the inferior mesenteric artery (IMA). We then dissected the IMA at the height immediately after the left colic artery diverged and then performed rectal and mesenteric detachment. As we peeled the rectum from the front of the sacrum and proceeded toward the anus, we encountered the levator ani muscle. After switching the scope to the near-infrared observation mode while further peeling toward the anus and paying attention to the levator ani muscle, the luminescent gauze was observed through the back of the tissue. As the fibrous tissue was exfoliated, the fluorescent gauze gradually became see-through. When the tissue was further incised with an electric knife at the site where the fluorescence was strong, the gauze was finally exposed to the naked eye. We then proceeded with rectal detachment to expose the entirety of gauze while relying on fluorescent ICG and paying attention to the prostate, seminal vesicles, and neurovascular bundle, which allowed us to safely reach the detached layer from the anal side (Figure 3). Thereafter, we returned to the transanal surgery once more. The intestinal tract was dragged out of the anus and the sigmoid colon was dissected to remove the specimen. Afterwards hat, the sigmoid colon and the residual rectum were sutured with a total of 16 needles around the circumference with a 4-0 monofilament absorbent thread in all layers and anastomosed. We then confirmed the absence of intra-abdominal bleeding via laparoscopy, after which a temporary ileal-covering stoma was finally constructed and the surgery was completed. The operative time and blood loss were 293 min and 5 mL, respectively.