Intra‐operative indocyanine green fluorescence imaging

Table ​Table22 demonstrates the clinicopathological characteristics of the participants. The specimens were four male patients (median age 58 years, range 47–62 years; tumour distance from the anal verge 5.5 cm, range 3–7 cm; Stage I–IIIB [20]; operative procedures APR (N = 1), low anterior resection (N = 3); all four patients received preoperative chemotherapy) who underwent laparoscopic or robotic surgery for lower RC at Hirosaki University Hospital between January and March 2019. This study was approved by the Human Research Ethics Committee at Hirosaki University Graduate School of Medicine (reference no. 2017‐044 and 2018‐134). Informed consent was obtained from all participants.

Clinicopathological characteristics of patients undergoing ICG‐IF

Abbreviations: Adenocarcinoma‐mod, moderately differentiated adenocarcinoma; Adenocarcinoma‐well, well differentiated adenocarccinoma; APR, abdominoperineal resection; AV, anal verge; BMI, body mass index; FOLFOX, fluorouracil, leucovorin and oxaliplatin; ICG‐FI, indocyanine green fluorescence imaging; LAR, low anterior resection; SOX, S‐1 and oxaliplatin.

ICG solution was prepared in the same manner as described in a previous study evaluating lymphatic flow in the colon [21]. Twenty‐five milligrams ICG powder (Diagnogreen; Daiichi Pharmaceuticals) was dissolved in 10 ml distilled water. The patient was administered general anaesthesia, and then 0.1 ml (0.25 mg) of the dye solution was injected into the submucosa at the dentate line (3 cm oral side from the anal verge) at the anterior, posterior and bilateral walls prior to the initiation of the operation. After completing a total mesorectal excision, the lymph flow around the anal canal was observed using a laparoscopic near‐infrared camera (1588 AIM camera system; Stryker).

From the collected data, schemas of the functional lymphovascular network of the anorectal region were generated using illustration software, Adobe Illustrator CC (Adobe Systems). Schemas were illustrated according to observations in our study and a previous report by Tsukada et al. [13].