Cylindrical abdominoperineal resection for rectal cancer using the Hugo RAS system: The first ever case report for rectal cancer.

In May 2023, the Hugo RAS system obtained pharmaceutical approval for use in gastroenterological surgery in Japan. It is expected to be particularly effective in rectal cancer surgery, which require the manipulation of the deep pelvic cavity and communication with surgeons operating from the intraperitoneal and anal approaches. A 68-year-old woman presented to our hospital with bloody stools and was diagnosed with cStage I (cT2N0M0) rectal cancer and underwent abdominoperineal resection employing the Hugo RAS system. Two arm carts were placed on the left and right lateral sides with an interleg space, and trocars were placed in a straight line between the right superior iliac spine and umbilicus. Herein, we report the first abdominoperineal resection for rectal cancer using the Hugo RAS system.

A first report of right-hemicolectomy for ascending colon cancer in Japan with the da Vinci SP surgical robot system.

BACKGROUND: The da Vinci SP robotic surgical system received regulatory approval for use in colorectal cancer surgery in Japan in April 2023. Given the advantages of the precision of a robot and the postoperative cosmesis of single-site surgery, the system is expected to be further utilized for minimally invasive surgeries, in addition to the curative and safety-assured laparoscopic technique. CASE PRESENTATION: A 73-year-old man presented at our hospital with positive fecal occult blood. He was diagnosed with cT2N0M0 (Stage I) ascending colon cancer and underwent a right hemicolectomy, which was performed with the da Vinci SP system. The operation was performed safely, and the patient was discharged without complications. Pathology findings showed that complete mesocolic excision was achieved. CONCLUSIONS: Herein, we report the first colorectal cancer surgery performed using the da Vinci SP system in Japan. The use of this robotic surgical system with access forms for right hemicolectomy is safe and oncologically appropriate.

CD8-positive T Cell Infiltration With Human Leukocyte Antigen Class 1 Expression Predicts Patients With Stage IV Colorectal Cancer Survival.

BACKGROUND/AIM: The immune microenvironment in cancer correlates with cancer progression and patient prognosis. Cancer immune microenvironment evaluation, based on CD3+ and CD8+ T cell infiltration at the center and invasive margin of the tumor, is defined as the immunoscore. An international multicenter analysis revealed that the immunoscore can accurately predict the prognosis of patients with colorectal cancer (CRC) (stage I, II, and III). However, no markers are currently available to predict the prognosis in patients with stage IV CRC. We thus aimed to analyze the immune microenvironment in patients with stage IV CRC in this study. PATIENTS AND METHODS: We analyzed the immune microenvironment of patients with stage IV CRC using immunohistochemical (IHC) staining. We evaluated the expressions of CD8 and the cases were divided into CD8 high (CD8Hi) and CD8 low (CD8Low) groups according to median CD8 expression. HLA class 1 (HLA1) expression was also evaluated using IHC staining and the cases were divided into HLA1Hi group and HLA1Low group according to 50% of HLA1 expression rate. CD8×HLA1 score was defined by the combination of CD8 and HLA1 expressions. RESULTS: CD8Hi and HLA1Hi cases were associated with better prognosis compared with CD8Low and HLA1Low cases according to a log-rank test, respectively. We defined a novel biomarker by combining CD8+ T-cell infiltration and HLA1 expression, referred to as the CD8×HLA1 score. We found that CD8×HLA1Hi cases predicted patient prognosis better than CD8×HLA1Int and CD8×HLA1Low according to a log-rank test. CONCLUSION: The combination of CD8+ T cell infiltration and HLA1 expression is crucial for cancer immune microenvironment evaluation in CRCs.

Tele-proctoring for minimally invasive surgery across Japan: An initial step toward a new approach to improving the disparity of surgical care and supporting surgical education.

Aim: The aim of this study was to verify the clinical feasibility of tele-proctoring using our ultra-low latency communication system with shared internet access. Methods: Connections between two multiple remote locations at various distances were established through the TELEPRO® tele-proctoring system. The server records the latency between the two locations for tele-proctoring using the annotations. Questionnaires were administered to the surgeons, assistants, and medical staff. Respondents rated the quickness and quality of communication in terms of latency and disturbances in the audio, video, and usefulness of the live telestrations with annotation. Results: Seven hospitals tele-proctored with Sapporo Medical University between January 2021 and September 2022. The median latency of annotation between the two locations ranged from 24.5 to 48.5 ms. No major technological problems occurred, such as streaming interruption, loss of video or audio, poor resolution. The video encoding time was 10 ms, and its decoding time was 0.8 ms. The total latency positively correlated with the distance between two locations (R = 0.55, p < 0.01). The quality of communication regarding latency, disturbance, and surgical education with intraoperative annotative instructions showed similar trends, with perfectly fine being the most common response. No significant differences in surgical quality, educational effect, or social impact were observed between the latency ≥30 and <30 ms groups for whether the size of latency affects surgical education. Conclusion: The feasibility of the tele-proctoring system is expected to be a sustainable approach to help education for young surgeons and surgical supports in rural areas, thereby reducing disparities in health care.

Safety and short-term outcomes of robotic-assisted transabdominal preperitoneal repair for inguinal hernia in pioneering hospitals in Japan: A nationwide retrospective cohort study.

INTRODUCTION: We aimed to evaluate the safety and short-term outcomes of robotic-assisted transabdominal preperitoneal repair for inguinal hernia in 12 pioneering hospitals in Japan. METHODS: Clinical data of patients who underwent robotic-assisted transabdominal preperitoneal repair between September 1, 2016, and December 31, 2021 were collected. Primary outcome measures were intra-operative adverse events and post-operative complications, whereas secondary outcomes were surgical outcomes, including chronic pain, recurrence, and learning curve. RESULTS: In total, 307 patients were included. One case of inferior epigastric arterial injury was reported; no cases of bowel or bladder injury were reported. Thirty-five seromas were observed, including four (1.3%) cases that required aspiration. The median operative time of a unilateral case was 108 minutes (interquartile range: 89.8-125.5), and post-operative pain was rated 1 (interquartile range: 0-2) on the numerical rating scale. In complicated cases, such as recurrent inguinal hernias and robotic-assisted radical prostatectomy-associated hernias, dissection and suture were safely achieved, and no complications were observed, except for non-symptomatic seroma. All patients underwent robotic procedures, and there was no chronic post-operative inguinal pain, although one case of hernia recurrence was reported. Regarding the learning curve, plateau performance was achieved after 7-10 cases in terms of operative time (P < .001). CONCLUSION: Robotic-assisted transabdominal preperitoneal repair can be safely introduced in Japan. Regardless of the involvement of many surgeons, the mastery of robotic techniques was achieved relatively quickly. The advantage of robotic technology such as wristed instruments may expand the application of minimally invasive hernia repair for complicated cases.

World-first report of low anterior resection for rectal cancer with the hinotori™ Surgical Robot System: a case report.

BACKGROUND: The hinotori™ Surgical Robot System was approved for use in colorectal cancer surgery in Japan in 2022. This robot has advantages, such as an operation arm with eight axes, an adjustable arm base, and a flexible three-dimensional viewer, and is expected to be utilized in rectal cancer surgery. Herein, we report the world's first surgery for rectal cancer using the hinotori™ Surgical Robot System. CASE PRESENTATION: A 71-year-old woman presented to our hospital with bloody stools. A colonoscopy revealed type 2 advanced cancer in the rectum, and a histological examination exposed a well-differentiated adenocarcinoma. Abdominal enhanced computed tomography divulged rectal wall thickening without significant swelling of the lymph nodes or distant metastasis. Pelvic magnetic resonance imaging showed tumor invasion beyond the intrinsic rectal muscle layer. The patient was diagnosed with cStage IIa (cT3N0M0) rectal cancer and underwent low anterior resection using the hinotori™ Surgical Robot System. Based on an adequate simulation, surgery was safely performed with appropriate port placement and arm base-angle adjustment. The operating time was 262 min, with a cockpit time of 134 min. Subsequently, the patient was discharged 10 days postoperatively without complications. The pathological diagnosis was pStage IIA (cT3N0M0) and the circumferential resection margin was 6 mm. CONCLUSIONS: We report the first case of low anterior resection for rectal cancer using the hinotori™ Surgical Robot System, in which a safe and appropriate oncological surgery was performed.

Right hemicolectomy for ascending colon cancer using the hinotori surgical robot system: The first ever case report for colon cancer.

The hinotori Surgical Robot System obtained pharmaceutical approval for use in colorectal cancer surgery in October 2022 in Japan, and its advantages, including its operating arm with eight axes, adjustable arm base, and flexible 3D viewer, are expected to be utilized in colon cancer surgery. A 68-year-old woman presented to our hospital with abdominal pain and was diagnosed with cStageIIa (cT3N0M0) ascending colon cancer and underwent right hemicolectomy using the hinotori Surgical Robot System with the appropriate port placement on the arc around the hepatic flexure, which was available for both ileocecal manipulation and lymph node dissection, and adjustment of the angle of the arm base to further reduce interference. Herein we report the world's first surgery for colorectal cancer using the hinotori Surgical Robot System.

Essential updates 2020/2021: Advancing precision medicine for comprehensive rectal cancer treatment.

In the paradigm shift related to rectal cancer treatment, we have to understand a variety of new emerging topics to provide appropriate treatment for individual patients as precision medicine. However, information on surgery, genomic medicine, and pharmacotherapy is highly specialized and subdivided, creating a barrier to achieving thorough knowledge. In this review, we summarize the perspective for rectal cancer treatment and management from the current standard-of-care to the latest findings to help optimize treatment strategy.

Development of an ultralow-latency communication system using shared internet access: promoting the implementation of telemedicine.

Telemedicine is becoming increasingly important to address the shortage of gastrointestinal surgeons and disparities in domestic and international treatment outcomes for patients with colorectal cancer. The development of a low-latency communication system using existing communication infrastructure (shared internet access: SIA) is necessary to promote the use of telemedicine. The aim of this study was to develop a low-latency communication system using SIA. We conducted an experiment between Sapporo and Tokyo using an ultralow-latency communication system for remote medical education (TELEPRO®). The latency was measured using 2000 annotations from a monitor in Sapporo, which confirmed a median latency of 27.5 ms. A low-latency communication system based on SIA with latency lower than the maximum allowable latency for telemedicine was developed successfully.

Artificial intelligence-based technology to make a three-dimensional pelvic model for preoperative simulation of rectal cancer surgery using MRI.

Aim: A new technique that allows visualization of whole pelvic organs with high accuracy and usability is needed for preoperative simulation in advanced rectal cancer surgery. In this study, we developed an automated algorithm to create a three-dimensional (3D) model from pelvic MRI using artificial intelligence (AI) technology. Methods: This study included a total of 143 patients who underwent 3D MRI in a preoperative examination for rectal cancer. The training dataset included 133 patients, in which ground truth labels were created for pelvic vessels, nerves, and bone. A 3D variant of U-net was used for the network architecture. Ten patients who underwent lateral lymph node dissection were used as a validation dataset. The correctness of the vascular labelling was assessed for pelvic vessels and the Dice similarity coefficients calculated for pelvic bone. Results: An automatic segmentation algorithm that extracts the artery, vein, nerve, and pelvic bone was developed, automatically producing a 3D image of the entire pelvis. The total time needed for segmentation was 133 seconds. The success rate of the AI-based segmentation was 100% for the common and external iliac vessels, but the rates for the vesical vein (75%), superior gluteal vein (60%), or accessory obturator vein (63%) were suboptimal. Regarding pelvic bone, the average Dice similarity coefficient between manual and automatic segmentation was 0.97 (standard deviation 0.0043). Conclusion: Though there is room to improve the segmentation accuracy, the algorithm developed in this study can be utilized for surgical simulation in the treatment of advanced rectal cancer.

Artificial intelligence-based technology for semi-automated segmentation of rectal cancer using high-resolution MRI.

AIM: Although MRI has a substantial role in directing treatment decisions for locally advanced rectal cancer, precise interpretation of the findings is not necessarily available at every institution. In this study, we aimed to develop artificial intelligence-based software for the segmentation of rectal cancer that can be used for staging to optimize treatment strategy and for preoperative surgical simulation. METHOD: Images from a total of 201 patients who underwent preoperative MRI were analyzed for training data. The resected specimen was processed in a circular shape in 103 cases. Using these datasets, ground-truth labels were prepared by annotating MR images with ground-truth segmentation labels of tumor area based on pathologically confirmed lesions. In addition, the areas of rectum and mesorectum were also labeled. An automatic segmentation algorithm was developed using a U-net deep neural network. RESULTS: The developed algorithm could estimate the area of the tumor, rectum, and mesorectum. The Dice similarity coefficients between manual and automatic segmentation were 0.727, 0.930, and 0.917 for tumor, rectum, and mesorectum, respectively. The T2/T3 diagnostic sensitivity, specificity, and overall accuracy were 0.773, 0.768, and 0.771, respectively. CONCLUSION: This algorithm can provide objective analysis of MR images at any institution, and aid risk stratification in rectal cancer and the tailoring of individual treatments. Moreover, it can be used for surgical simulations.

Feasibility of the semi-opened method of specimen resection for a circumferential resection margin in rectal cancer surgery: a multicenter study.

PURPOSE: A circumferential resection margin (CRM) > 1 mm is a surrogate marker of oncologic outcomes in rectal cancer patients. In Japan, because the mesentery is removed from the rectum, the CRM cannot be measured. This multicenter prospective study evaluates the feasibility of a resected specimen processing method that allows CRM measurement. METHODS: Fifty patients with rectal cancer were enrolled. Resected specimens were processed as previously reported. The primary outcomes were CRM measurement and the rate of CRM positivity. The secondary outcomes were the quality of total mesorectal excision, the possibility to visualize and sample the tumor, the number of harvested lymph nodes, and comparison between the pathological CRM and preoperative mesorectal fascia (MRF) involvement. This study was registered in the University Hospital Medical Information Network (UMIN) Clinical Trials Registry under identification number UMIN000031735. RESULTS: The CRM was measurable in all patients and found to be positive in three (6%). We confirmed tumor localization, sampled the tumor, and measured the distal margin in all patients. A median of 20 lymph nodes were harvested. The concordance rate between preoperative MRF involvement and pathological CRM status was 90%. CONCLUSION: A semi-opened rectal specimen with transverse slicing is a feasible method for measuring the CRM.

Defecation disorder and anal function after surgery for lower rectal cancer in elderly patients.

AIM: This study aims to investigate the association of patient age with defecation disorders and anal function after lower rectal cancer surgery. METHODS: We retrospectively reviewed the data of 141 consecutive patients with lower rectal cancer who underwent sphincter-preserving operation. The patients were classified into five categories by age thresholds at 65, 70, 75, 80, and 85 years, for disaggregate analysis. Anal manometry was used for measuring the maximum resting pressure, high-pressure zone, and maximum squeeze pressure. Anal manometry was performed preoperatively and at 3, 6, 9, and 12 months postoperatively. The Wexner and low anterior resection syndrome scores were assessed at 1, 3, 6, 9, and 12 months after rectal surgery or stoma closure for patients with ileostomy. RESULTS: The data of 117 patients were reviewed. No significant differences were found between the younger and elderly groups in any characteristics across the six age groups. The preoperative intra-anal pressures of the elderly patients were slightly lower than those of the younger patients; however, there was no significant difference in the course of postoperative intra-anal pressures. Defecation disorder, as measured by the Wexner and low anterior resection syndrome scores, improved significantly in elderly patients compared to younger patients. CONCLUSION: There was no significant difference in the course of postoperative intra-anal pressures between the elderly and younger patients. However, defecation disorders in elderly patients significantly improved compared with younger patients. Sphincter-preserving operation can be a viable treatment option for active elderly patients.

Clinical Utility and Characteristics of the LARS Score Compared to the CCIS.

PURPOSE: The low anterior resection syndrome (LARS) score (LS) has been widely validated and has become an international tool for evaluating postoperative bowel dysfunction. However, many physicians still use the conventional incontinence scores in LARS treatment. Moreover, interpretation of LS and its relationship with conventional incontinence scores are not yet well understood. Here we compared the LS with the Cleveland Clinic Incontinence Score (CCIS) to clarify the clinical utility and characteristics of the LARS score. METHODS: We performed a multicentre observational study, recruiting 246 rectal cancer patients following sphincter-preserving surgery. Patients completed the LS, CCIS, and SF36 questionnaires. RESULTS: The response rate was 76.4%, and a total of 180 patients were analysed. The LS was strongly correlated with the CCIS (P < 0.001, rs = 0.727). However, among 116 patients determined to not have incontinence (CCIS 0-5), 51 (44%) were diagnosed with LARS (29 with minor LARS and 22 with major LARS). Among 68 patients without LARS, only 3 were diagnosed as having incontinence (CCIS > 6). In comparison with background factors, aging and elapsed time were associated with only LS. High LS and CCIS both showed significant quality-of-life impairment as assessed by the SF-36. CONCLUSION: This is the first study to determine the difference in the numeric values between the CCIS and LS. The LS can be a convenient tool for LARS screening, identifying a wide range of patients with LARS, including those with incontinence evaluated by CCIS. Assessment using the CCIS may often underestimate LARS.

Short-Term Outcomes with Standardized Transperineal Minimally Invasive Abdominoperineal Excision for Rectal Cancer.

BACKGROUND: Transperineal abdominoperineal excision (TpAPE) is an emerging approach for low rectal cancers but is technically challenging. Based on an anatomical study we conducted previously, we have standardized the TpAPE procedure. Here, we aimed to validate the feasibility of the standardized TpAPE by investigating the short-term outcomes. METHODS: From January 2018 to November 2020, a total of 405 patients underwent laparoscopic or robotic rectal resection for rectal cancer in our institution. For the current study, we analyzed data for the 31 patients who underwent TpAPE. The abdominal phase was performed synchronously with the perineal phase using either a laparoscopic or robotic approach. Short-term outcomes included operative and pathological results. RESULTS: Of the 31 cases, we identified anterior quadrant tumor invasion in 21. Most of the cases were advanced, with 6 staged as cT3 and 20 as T4. Of the 27 cases not involving distant metastasis, neoadjuvant therapy was performed in 19. No inadvertent rectal perforation or urethral injury was found intraoperatively. The median procedural duration to specimen removal was 250 min (interquartile range, 204-287), and the median intraoperative blood loss was 10 ml (interquartile range, 5-40). Regarding postoperative complications, perineal wound infection developed in 11 cases. A positive circumferential resection margin was found in 3, corresponding to the positive rate of 9.7%. These three cases were among the first 12 cases involving standardized TpAPE. CONCLUSIONS: The current results indicate that TpAPE can be performed safely and might represent a useful option for low rectal cancer resection.

A modified method for resected specimen processing in rectal cancer: Semi-opened with transverse slicing for measuring of the circumferential resection margin.

Circumferential resection margin (CRM) is essential for oncological quality assessment in rectal cancer surgery. CRM represents a surrogate parameter for oncological outcomes and is important for stratifying treatment strategies in Western nations. In Japan, the mesentery is removed for specimen processing in order to extract as many lymph nodes (LNs) as possible; consequently, CRM cannot be measured. Given the diversification of treatment strategies for rectal cancer, the lack of measurement of CRM to assess surgical outcomes is a crucial issue that must be resolved. Therefore, it is necessary to establish a method enabling measurement of CRM while enjoying the advantages of the Japanese method. In the method we developed, the mesentery is removed from the rectum more than 2 cm away from the tumor, and the vicinity of the tumor is circularized. It is necessary to investigate the usefulness of this method prospectively in a multi-center study.

Snapshots of lymphatic pathways in colorectal cancer surgery using near-infrared fluorescence, in vivo and ex vivo.

INTRODUCTION: Indocyanine green (ICG) fluorescence imaging has been used for blood flow assessment in anastomoses in the field of colorectal cancer surgery. However, whether ICG fluorescence is related to the presence of cancer cells in the lymph nodes is unclear. We explored the utilization of ICG fluorescence in colorectal cancer surgery. MATERIALS AND METHODS: ICG was injected into the submucosa around the tumor before radical resection in colorectal cancer patients. Intraoperatively, near-infrared (NIR) fluorescence was used for lymphatic flow visualization. After specimen removal, harvested lymph nodes were classified as positive or negative based on the detection of fluorescence, followed by pathological examination. ICG distribution on a section of each lymph node was examined by fluorescence microscopy. RESULTS: Overall, 155 patients underwent real-time NIR fluorescence imaging-guided surgery. Altogether, 1,017 lymph nodes were retrieved from these patients. Metastatic lymph nodes were present in 36 (5.8%) of 622 fluorescence-negative lymph nodes, which was significantly higher than 11 (2.8%) of 395 fluorescence-positive lymph nodes (odds ratio: 2.15, P = 0.03). Fluorescence microscopy of metastatic lymph nodes showed that ICG fluorescence was present in the normal structural region but not in the cancerous region of the lymph nodes. Furthermore, ICG fluorescence was observed in all metastatic lymph nodes, except those with cancer cells occupying >90% of the total area. CONCLUSIONS: ICG fluorescence detected only the normal parts of the lymph node draining from the peritumoral area and not the cancer tissues. This finding is important for developing appropriate strategies for navigation surgery using NIR fluorescence.

Laparoscopic low anterior resection for rectal cancer wherein the inferior mesenteric artery arose from the superior mesenteric artery: a case report.

BACKGROUND: Few cases have been reported of colorectal cancer with inferior mesenteric artery (IMA) branching abnormalities; therefore, the lymphatic flow in such cases remains unknown. We report the first case of locally advanced rectal cancer in which the IMA arose from the superior mesenteric artery (SMA) in which we achieved to visualize the lymphatic flow. CASE PRESENTATION: A 65-year-old woman complaining of bloody stools was investigated in our hospital and suspected with rectal cancer. Colonoscopy and abdominal enhanced computed tomography (CT) revealed a circumscribed, localized ulcerative tumor in the rectum. 3-Dimensional contrast-enhanced computed tomography (3D-CT) showed that the IMA arose from the SMA. The patient was diagnosed with rectal cancer (cT3N0M0, cStage IIa) and laparoscopic low anterior resection was performed. The sigmoid colon was resected using the medial approach. Only the plexus of the colic branch of the lumbar splanchnic nerve was observed at the site where the root of the IMA usually exists and showed interruption of the indocyanine green (ICG) fluorescence-illuminated lymphatics. The root of the IMA was ligated, and Japanese D3 lymphadenectomy was performed, preserving the accessory middle colic artery. All fluorescent lymph nodes were resected. The pathological diagnosis was pT4aN1aM0 stage IIIb. The patient's postoperative course was uneventful. Adjuvant chemotherapy was administered, and the patient was recurrence-free at 1.5 years after surgery. CONCLUSIONS: We were able to perform safe and appropriate surgery oncologically, despite abnormal vascular anatomy, due to preoperative identification using 3D-CT and intraoperative navigation using ICG administration.

Feasibility of Pooled One-Step Nucleic Acid Amplification for Molecular Staging of Pathologically Node-Negative Colon Cancer: A Prospective Multicenter Study.

BACKGROUND: Although conventional one-step nucleic acid amplification (OSNA) is a useful molecular-staging method, its complexity hinders its use in clinical practice. A pooled approach for OSNA (pOSNA) has been evaluated for its feasibility in pathologically node-negative colon cancer (pNNCC) for molecular staging of lymph node metastasis in clinical practice. METHODS: Subjects were patients diagnosed with clinical stage II-IIIA colon cancer between January 2017 and September 2018. pOSNA involved harvesting pericolic lymph nodes from fresh surgical specimens, cutting them in half, placing 50% of the nodes in a single test tube, and performing the OSNA assay. The remaining halved pericolic, intermediate, and main lymph nodes were submitted for histopathologic examination, with metastasis determined by hematoxylin and eosin staining of a cut surface of each node. RESULTS: Of the 98 enrolled patients, 92 formed the analysis set. The mean number of harvested lymph nodes per case was 24.3 (range 5-66) and the mean number of lymph nodes used for pOSNA analysis was 6.9 (range 1-35). The concordance rate, sensitivity, and specificity between methods were 89.1%, 84.6% (95% confidence interval [CI] 0.80-0.91), and 90.9% (95% CI 0.88-0.94), respectively. The pOSNA upstaging rate for node-negative patients was 9.1% (6/66), and pOSNA returned false-negative results in 15.4% of node-positive cases (4/26). CONCLUSIONS: pOSNA demonstrated an upstaging rate for pNNCC equivalent to that in previous studies, suggesting its feasibility for molecular staging of pNNCC in clinical practice.

MRI-detected extramural vascular invasion potentiates the risk for pathological metastasis to the lateral lymph nodes in rectal cancer.

PURPOSE: Multidisciplinary treatment for locally advanced rectal cancer requires an accurate assessment of the risk of metastasis to the lateral lymph nodes (LNs). We herein aimed to stratify the risk of pathological metastasis to lateral LNs based on the preoperatively detected malignant features. METHODS: All patients with rectal cancer who underwent surgery from January 2016 to July 2020 were identified. We recorded the TNM factors; perirectal and lateral LN sizes; and MRI findings, including mesorectal fascia involvement, extramural vascular invasion (EMVI), tumor site, and tumor distance from the anal verge. RESULTS: 101 patients underwent rectal resection with lateral lymph node dissection, of whom 16 (15.8%) exhibited pathological metastases to the lateral LNs. Univariate analyses demonstrated that lateral LN metastasis was significantly correlated with mrEMVI positivity (p = 0.0023) and a baseline lateral LN short-axis length of ≥ 5 mm (p < 0.0001). These significant associations were confirmed by a multivariate analysis (p = 0.0254 and 0.0027, respectively). The lateral LN metastasis rate was as high as 44% in cases bearing both risk factors, compared to 0% in cases lacking both risk factors. CONCLUSION: The results elucidated in this study may contribute to risk stratification, which can be used when determining the indications for lateral lymph node dissection.