The rapid advancement of deep learning technology in the 2010s accelerated the development of artificial intelligence (AI) in the field of colonoscopy, leading to the approval of EndoBRAIN, Japan's first AI medical device, in 2018. Currently, computer-aided detection (CADe) for lesion detection support and computer-aided diagnosis (CADx) for differential diagnosis support are being clinically applied, contributing to improved adenoma detection rates (ADR) and enhanced diagnostic accuracy. Multiple randomized controlled trials on CADe have demonstrated an approximately 10% improvement in ADR. In CADx, diagnostic accuracy comparable to that of expert physicians has been achieved for differentiating between neoplastic and non-neoplastic lesions, and more sophisticated diagnostic support systems have been developed for diagnosing depth of invasion and identifying sessile serrated lesions (SSL). Additionally, new areas of application are expanding, including AI for predicting lymph node metastasis through pathological image analysis and computer-aided quality improvement (CAQ) systems aimed at improving examination quality. However, verification of the long-term effects of these AI technologies on cancer mortality and incidence suppression remains an important future challenge.

Colorectal peritoneal metastasis (CPM) has long been considered a terminal condition with poor prognosis, due to its diffuse spread and limited responsiveness to systemic chemotherapy. However, recent advances in surgical strategies have changed this perspective. In Western countries, in appropriately selected patients, cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC) has achieved 5-year survival rates of 30-45%, and is becoming established as a standard treatment. CRS aims to remove all visible tumors, and HIPEC targets microscopic residual disease with heated intraperitoneal chemotherapy, offering pharmacokinetic advantages. Prognostic indicators such as the Peritoneal Cancer Index (PCI) and completeness of cytoreduction (CC) score are key for patient selection, and refined diagnostic approaches such as staging laparoscopy and advanced imaging are increasingly being utilized. Recent randomized controlled trials have reported that the additional benefit of HIPEC has not been clearly demonstrated. In Japan, the mainstay treatment remains localized peritonectomy (tumor debulking) for limited CPM (P1/P2), which also shows favorable outcomes. However, CRS+HIPEC is still limited to specialized centers. In future, further accumulation of evidence and validation through prospective comparative trials are essential to optimize treatment selection and expand the role of CRS+HIPEC in Japan.

Neoadjuvant therapy is a widely accepted standard treatment for locally advanced rectal cancer in Western countries. Total neoadjuvant therapy (TNT) is a novel strategy that delivers both (chemo) radiotherapy and systemic chemotherapy before surgery, aiming to enhance local control and address the limited effect of (chemo) radiotherapy on distant metastases. Multiple TNT regimens are currently available, varying in combinations such as long-course chemoradiotherapy or short-course radiotherapy, as well as in the type and duration of chemotherapy used. Although evidence on TNT is rapidly evolving with data from several clinical trials, no definitive consensus has yet been reached regarding optimal regimen selection. Clinicians must understand the advantages and limitations of each regimen to tailor TNT to individual patients. Multidisciplinary decision-making based on local and systemic risk is essential to maximizing the benefit of TNT for patient outcomes.

Anal canal squamous intraepithelial lesions and squamous cell carcinoma are rare diseases, both of which are associated with human papillomavirus (HPV) infection. Identified risk factors include a history of homosexual intercourse and human immunodeficiency virus (HIV) infection. Although these lesions are infrequently encountered in Japan, increasing awareness has led to a rise in reports of early-stage detection. Given the significant impact of anal lesions on patients' quality of life, early diagnosis is crucial. Careful rectal retroflexion and thorough inspection of the anal canal using magnifying endoscopy with narrow band imaging (NBI) or blue laser imaging (BLI) may facilitate early detection.

Anal canal cancer is an uncommon tumor worldwide, and its incidence rate is also low in Japan. The histological type of anal canal cancer is predominantly squamous cell carcinoma in Western countries, whereas in Japan, most cases are adenocarcinomas. Regarding HPV infection in anal canal squamous cell carcinoma, the HPV positivity rate is also very high in Japan, similar to Western countries, with HPV-16 being the most common genotype. Additionally, the classifications and guidelines for anal canal cancer vary depending on the site of origin and histological type. In Japan, for rectal-type adenocarcinomas, the Japanese Classification of Colorectal, Appendiceal, and Anal Carcinoma 9th edition is used, while for squamous cell carcinomas, adenocarcinoma of anal glands and adenocarcinoma associated with anorectal fistula, the UICC TNM classification 8th edition is used. Regarding treatment, surgical therapy is the primary treatment for adenocarcinoma cases, while chemoradiotherapy is the primary treatment for squamous cell carcinoma cases. However, there are few reports on anal canal cancer both in Japan and internationally. Therefore, it is important to accumulate more cases and establish appropriate classifications and treatment guidelines in the future.

Ulcerative colitis is a well-known risk factor for colorectal cancer. Unlike in Western countries, the anorectum is the most frequent site of Crohn's disease-associated neoplasia in Japan.

In 2024, new clinical guidelines on inflammatory bowel disease (IBD)-associated gastrointestinal tumors were published. Registry studies are underway by the Japanese Society for Cancer of the Colon and Rectum and a research team supported by the Ministry of Health, Labour and Welfare.

Surveillance colonoscopy is essential, with total proctocolectomy generally recommended for ulcerative colitis-associated colorectal neoplasia. Under strict surveillance for metachronous and synchronous multiple lesions, endoscopic treatment for low-grade dysplasia may be performed, and registry studies are currently ongoing.

Early detection of anorectal tumors associated with Crohn's disease is often difficult. Abdominoperineal resection or even more extensive surgery is frequently required. Although a definitive diagnostic method has not yet been established, surveillance combining multiple imaging modalities such as colonoscopy and MRI, along with examination and biopsy under anesthesia, is being explored.

Rectal prolapse is a protrusion of the entire thickness of the rectal wall through the anal sphincter; it is an obstacle to social life, and is often accompanied by fecal incontinence. The causes are considered to be: (1) diastasis of levator ani, (2) abnormally deep cul-de-sac, (3) redundant sigmoid colon, (4) patulous anal sphincter, and (5) loss of horizontal position of the rectum and its sacral attachment. The diagnosis can be easily made by confirming the total circumferential cylindrical prolapse of the rectum transanally. Historically, various surgical procedures have been developed, and many institutions tend to employ the methods with which they are most proficient. In general, it is considered that the abdominal approach is more invasive and has fewer recurrences, but that the perineal approach is less invasive and has more recurrences. Considering that this disease is common in the elderly, when selecting the surgical method it is important to consider the patient's general health condition carefully, the preferences of both the patient and their family, and the curability. This paper provides an overview of the causes, diagnosis, and treatment of rectal prolapse.

The Gant-Miwa-Thiersch procedure can be performed relatively easily and safely under spinal or local anesthesia, making it especially useful for this condition, which primarily affects the elderly. However, several complications have been reported, including high recurrence rates, postoperative bleeding or rectal perforation associated with the Gant-Miwa procedure, and constipation, mesh exposure, or infection related to the Thiersch procedure.

In recent years, the Leeds-Keio mesh－an artificial ligament made from elastic polyester mesh－has been approved for use in the Thiersch procedure. At our institution, we have performed the Gant-Miwa-Thiersch procedure using the Leeds-Keio mesh in over 100 cases. In this report, we present the key surgical techniques and postoperative outcomes.

As the population continues to age, the number of rectal prolapse cases is expected to rise. This article provides an overview of the historical evolution of the Gant-Miwa-Thiersch procedure, the key points of the surgical technique, as well as its advantages and challenges.

Transanal (transperineal) treatment of rectal prolapse, which is common in elderly patients, is considered to be an excellent treatment due to its minimal invasiveness. In our clinic, we perform the modified Delorme procedure by dividing and peeling off the external and internal mucosa of the prolapsed intestine. During the 6 years and 10 months from June 2017 to April 2024, we performed the modified Delorme procedure on 40 patients diagnosed with complete rectal prolapse.

There were 2 males and 38 females, and the median age was 81 years (50-91 years). The mean length of the prolapsed intestine was 4 cm (2-7 cm), the total length of mucosal resection was 11.4 cm (5-24 cm), and recurrence was observed in 6 cases (recurrence rate 15%). There were no deaths from surgery, but 1 patient (2.5%) experienced suture failure, and 5 patients (12.5%) experienced stenosis of the anastomosis.

The 34 patients who did not experience recurrence were evaluated for preoperative and postoperative anorectal manometry (maximum resting pressure, maximum squeeze pressure), Fecal Incontinence Severity Index (FISI), and Constipation Scoring System (CSS). All these scores improved significantly.

This study aimed to evaluate the efficacy and safety of the Altemeier procedure for rectal prolapse, particularly in elderly patients. A total of 120 patients who underwent the Altemeier procedure between December 2009 and December 2024 were retrospectively analyzed. Preoperative defecography was used to determine surgical indications. Risk factors for recurrence and outcomes were compared with those of rectopexy performed during the same period. The mean age was 81 years, and 117 patients were female. Clavien-Dindo grade II or higher complications occurred in 4.2% of Altemeier cases and 6.8% of rectopexy cases. Recurrence was observed in 38% of Altemeier cases and 6.8% of rectopexy cases. All five patients who underwent repeat Altemeier procedures experienced recurrence. Male sex, longer operative time, and prior rectal prolapse surgery were identified as significant risk factors for recurrence. The Altemeier procedure is a minimally invasive and safe option for elderly patients, but its higher recurrence rate compared to rectopexy remains a concern. Abdominal surgery should be considered for recurrent cases.

Rectal prolapse is a complex condition commonly seen in elderly women and often overlaps with various pelvic organ prolapses. Surgical treatment must be tailored to each patient's background and specific pathology. While rectopexy began with suture fixation, mesh-based techniques have become increasingly common due to their higher curative potential. Today, most procedures are performed laparoscopically, but specific anatomical challenges in pelvic organ prolapse patients－such as deep pelvic floors and organ descent－can hinder surgery and compromise outcomes if not addressed. Utilizing the pelvic-high lithotomy position and securing the surgical field with organ traction or vaginal retractors can effectively overcome these difficulties. Maintaining a clear surgical view and proper counter-traction allows precise rectal dissection along anatomical landmarks, followed by reliable fixation according to the selected surgical procedure. These strategies help ensure consistent and successful outcomes in rectopexy. This paper reviews the historical backgrounds, surgical innovations, and three representative procedures: suture rectopexy, the Wells procedure, and ventral mesh rectopexy.

Concomitant rectal prolapse and pelvic organ prolapse (POP) are relatively common, and their incidence is expected to increase with population aging. Surgical approaches for each condition include transabdominal (laparoscopic) and perineal methods, and combined procedures can allow simultaneous repair.

We reviewed 17 reports with our cases including 1,371 cases of combined repair and found a Clavien-Dindo grade IIIb or higher complication rate of 1.5%, with recurrence rates of 3.2% for rectal prolapse and 2.9% for POP, indicating favorable outcomes. In the past 10 years, 7 of 9 reports used a combination of laparoscopic ventral rectopexy and sacrocolpopexy (LSCVR), which is also our approach of choice. We describe our LSCVR technique in detail.

Although limited, reports of alternative combinations using transanal or perineal approaches also exist and may be suitable for certain patients. Surgical methods should be selected carefully, taking into account the conditions of individual patients.