A total of 120 patients with CRC who underwent minimally invasive radical surgery were included in the study. Inclusion criteria: 1- Histopathologically confirmed CRC; 2- Histopathological type belongs to adenocarcinoma; 3- Successfully completed laparoscopic radical resection + D3 lymph node dissection; 4- Elective surgery; 5- The same group of surgeons completed the operation. Exclusion criteria: 1- previous abdominal surgery; 2- emergency surgery; 3- CRC recurrence; 4- received neoadjuvant therapy before surgery; The study design conformed to the requirements of the Declaration of Helsinki. This study was conducted in accordance with the Declaration of Helsinki and approved by the Institutional Review Board of Longyan First Hospital of Fujian Province,informed consent was obtained from all subjects and/or their legal guardian(s).

The nanocarbon tracer was received from Chongqing Meilai Pharmaceutical Co., Ltd. (Chongqing, China). Indications for the application of nanocarbon tracers were as follows: Imaging is difficult to locate accurately; Radical surgery is performed after non-curative endoscopic biopsy surgery; Mechanical bowel preparation was performed 1–2 days before surgery, and the electronic colonoscope was placed under the microscope.The operation process followed to the protocol prvided by manufacturer strictly. To mark the location of the lesion, we pierced the submucosa at a 45° angle, injected 0.5 mL of 0.9% sodium chloride solution to stimulate the mucosal bulge, and then injected 0.1 mL of nanocarbon stock solution (Chongqing Laimei Pharmaceutical). If the endoscope could pass through the lesion area smoothly, we injected at 1 cm on the side of the lesion and 1 cm on the side of the anus (total 4 points); Each quadrant was injected separately (4 points in total).

Under general anesthesia and tracheal intubation, the surgical plan was determined according to the location of the lesion, and total mesocolectomy or total mesorectal excision was used to complete laparoscopic radical resection + D3 lymph node dissection;, Complete excision of the intestinal segment, mesentery and mesangial root lymphatic and adipose tissue where the lesion was located, and dissection of the paraintestinal, middle and central lymph nodes at the same time (Fig. 1).

The lymph nodes of the observation group were stained with nano-carbon

Review the clinicopathological data of the case records, including gender, age, height, age, lesion location, histopathological type, maximum diameter of the lesion, T stage, histological grade, vascular and nerve invasion, cancer nodule and lymph node detection, etc.

SPSS 24.0 software was used to analyze the data; gender, age, height, lesion location, histopathological type, maximum diameter of the lesion, T stage, histological grade, vascular and nerve invasion, cancer nodules and lymph node detection were included. A fixed-effect variable was used to calculate the propensity score; the propensity score was matched by the nearest neighbor matching method of 1:1, and the matching tolerance was 0.02; the Kolmogorov–Smirnov test was used to complete the normality evaluation, and the paired t test was used to compare the measurement data that conformed to the normal distribution., expressed as (x ± s); Mann–Whitney U test was used for comparison of measurement data that did not conform to the normal distribution, expressed as M (P25, P75); χ2 test was used for comparison of count data, expressed as rate; Poisson regression was used for multivariate analysis Multivariate model; P < 0.05 was considered statistically significant.