Backgrounds and study aim Placement of a self-expandable metallic stent (SEMS) has become a common practice for obstructive colorectal cancer. However, the safety and efficacy of systemic chemotherapy after SEMS placement remain unclear. Patients and methods This multicenter retrospective cohort study was conducted by the Japan Colonic Stent Safe Procedure Group across Japan to investigate the SEMS-related complications and clinical outcomes of chemotherapy in patients with unresectable obstructive colorectal cancer. Results A total of 289 patients were included in the study. The median duration from SEMS placement to chemotherapy initiation was 11 days (range, 6-21 days). SEMS-related complications occurred in 30.1% of the patients, with the most common complications being perforation (8.7%; 95% CI, 5.9-12.5A%), re-obstruction (19.4%), and migration (20.8%). Among the patients with stent migration, 30% required additional intervention. The median progression-free survival (PFS) was 9.2 months (95% confidence interval [CI], 7.5-10.9 months), and the median overall survival (OS) was 17.3 months (95% CI, 14.1-20.5 months). No significant difference in perforation rate was observed with or without bevacizumab use (14.5% vs. 7.3%, P < 0.107). Factors influencing survival outcomes included the number of metastatic organs, presence of perforation, and performance of primary tumor resection (PTR). Survival analyses showed that patients who underwent PTR had significantly better PFS and OS; however, this result should be interpreted with caution due to potential selection bias and immortal time bias inherent in the retrospective design. Conclusions This multicenter retrospective study demonstrated that while chemotherapy after SEMS placement is generally feasible, clinicians should remain vigilant for complications like perforation, migration, and re-obstruction.

AbstractRectal neuroendocrine tumor (NET) G1 is a docile-looking tumor. We herein report a 77-year-old male whose rectal NET G1 measuring 10 mm recurred eight years after endoscopic mucosal resection. Tumor recurrence was detected by his mild general fatigue. Abdominal computed tomography revealed widespread metastasis, including the liver, lymph nodes around the rectum, and cervical spines. Subsequent somatostatin receptor scintigraphy, as well as histological reassessment of previously resected specimen, proved that these metastatic diseases originated from the rectal NET G1 with vascular invasion and possible positive vertical margin. First, octreotide long-acting repeatable 30 mg i.m. was administered every four weeks. Second, transcatheter arterial chemoembolization (TACE) for multiple liver metastases and irradiation therapy for spinal metastasis were carried out. One year after these treatments started, everolimus (mTOR inhibitor) 10 mg p.o. was administered every day. For the last five years, he received two rounds of TACE treatments and one round of irradiation. Although recurrent diseases were temporally controlled by these multidisciplinary treatments for the last month, he died of multiple metastases six years later, after tumor recurrence was detected. This case underscores the potential for late recurrence even in rectal NET G1 with unfavorable histological features, highlighting the importance of long-term surveillance.

Colorectal cancer remains a leading cause of mortality worldwide, and early detection is essential for improving outcomes. CT colonography (CTC) has emerged as a promising alternative to optical colonoscopy for colorectal cancer screening. This article explores the potential of CTC in Japan, focusing on quality control, patient acceptability, complications, and its role in screening programs. CTC has demonstrated high sensitivity and specificity for detecting colorectal polyps, with its diagnostic performance comparable to colonoscopy for lesions ≥ 10 mm. Techniques such as fecal tagging and dual-position imaging significantly enhance diagnostic accuracy. However, the variability in diagnostic outcomes underscores the need for rigorous interpretation training and quality control. The American College of Radiology recommends training with at least 50 cases verified by colonoscopy. Despite its advantages, the adoption of CTC in Japan remains limited due to low awareness among medical professionals, a shortage of trained radiologists, and the absence of specific guidelines endorsing its use. Patient acceptability for CTC is high due to its non-invasive nature, shorter examination time, and reduced bowel preparation requirements compared to colonoscopy. Nonetheless, complications such as bowel perforation, albeit rare, necessitate careful risk assessment. While CTC has been recognized in the U.S. and Europe for screening and diagnostic follow-up, its integration into Japan’s colorectal cancer screening guidelines is crucial to expand its utilization. To maximize the benefits of CTC, efforts must focus on standardizing methodologies, establishing quality indicators, and generating robust evidence on mortality reduction and cost-effectiveness.

Computed tomography (CT) colonography is increasingly recognized as a valuable modality for diagnosing colorectal lesions, however, the interpretation workload remains challenging for physicians. Deep learning-based artificial intelligence (AI) algorithms have been employed for imaging diagnoses. In this study, we examined the sensitivity of neoplastic lesions in CT colonography images. Lesion location and size were evaluated during colonoscopy and a large-scale database including a dataset for AI learning and external validation was created. The DICOM data used as training data and internal validation data (total 453 patients) for this study were colorectal cancer screening test data from two multicenter joint trial conducted in Japan and data from two institutions. External validation data (137 patients) were from other two institutions. Lesions were categorized into ≥6 mm, 6 to 10 mm, and ≥10 mm. During this study, we adopted a neural network structure that was designed based on the faster R-CNNs to detect colorectal lesion. The sensitivity of detecting colorectal lesions was verified when one and two positions were integrated. Internal validation yielded sensitivity of 0.815, 0.738, and 0.883 for lesions ≥6 mm, 6 to 10 mm, and ≥10 mm, respectively, with a false lesion limit of three. Two external validation produced rates of 0.705 and 0.707, 0.575 and 0.573, and 0.760 and 0.779 for each lesion category. Combining two positions for each patient in calculating the sensitivity resulted in significantly improved rates for each lesion category. The sensitivity of CT colonography images using the AI algorithm was improved by integrating evaluations in two positions. Validation experiments involving radiologists who can interpret images as well as AI to determine the auxiliary diagnosis can reduce the workload of physicians.

AbstractBackgroundThe impact of obesity on colon cancer remains unclear. Very few studies of colon cancer surgery have analyzed body mass index (BMI) as a continuous variable, with no such reports from Japan. This study examined the association between BMI as a continuous variable and short‐ and long‐term outcomes of laparoscopic surgery for obese colon cancer patients.MethodsObese (BMI ≥25 kg/m2) patients who underwent laparoscopic radical surgery for Stage II/III colon cancer at 46 participating centers from 2009 to 2013 were included. Associations between short‐ and long‐term outcomes and BMI as a continuous variable were analyzed by univariate and multivariate regression models.ResultsAmong patients meeting the study criteria, 1036 were examined. BMI as a continuous variable correlated with log‐transformed operative time (regression coefficient: 0.02, 95% confidence interval [CI]: 0.012–0.028, p < 0.05) and blood loss (odds ratio: 1.089, 95% CI: 1.032–1.149, p < 0.05). There was no association between BMI continuous variables and 3‐year relapse‐free survival (RFS) and overall survival. However, 3‐year RFS was possibly better in patients with BMI ≥28.5 kg/m2 versus those with BMI <28.5 kg/m2 (hazard ratio: 0.682, 95% CI: 0.462–1.008, p = 0.055).ConclusionsThis study showed that BMI as a continuous variable correlated with operative time and blood loss. RFS was possibly better in the severely obese patients (BMI ≥28.5 kg/m2), suggesting that the prognosis for highly obese colon cancer patients appears to follow the obesity paradox.

Objectives: To investigate patient acceptance and preference for computed tomographic colonography (CTC) over colonoscopy. Methods: Participants were recruited from a nationwide multicenter trial in Japan to assess the accuracy of CTC detection. They were scheduled to undergo colonoscopy after CTC with common bowel preparation on the same day. Some were administered sedative drugs during colonoscopy, depending on the referring clinician and participant's preferences. The participants were requested to complete a questionnaire to evaluate the acceptability of bowel preparation, examinations, and preference for future examinations. Results: Of the 1,257 enrolled participants, 1,180 (mean age: 60.6 years; women: 43.3%) completed the questionnaire. Sedative drugs were not administered in 687 participants (unsedated colonoscopy group) and were administered intravenously during colonoscopy in 493 participants (sedated colonoscopy group). Before propensity score matching, the mean participants' age, percentages of asymptomatic participants, insufflation of gas during colonoscopy, and number of participants with a history of abdominal/pelvic operation significantly differed between the groups. After propensity score matching, 912 participants from each group were included in the analysis. In the unsedated colonoscopy group, CTC was answered as significantly easier than colonoscopy (p<0.001). Conversely, CTC was significantly more difficult than colonoscopy in the sedated colonoscopy group (p<0.001). In the unsedated colonoscopy group, 48% preferred CTC and 22% preferred colonoscopy for future examinations, whereas in the sedated colonoscopy group, 26% preferred CTC and 38% preferred colonoscopy (p<0.001). Conclusions: CTC has superior participant acceptability compared with unsedated colonoscopy. However, our study did not observe the advantages of CTC acceptance over sedative colonoscopy.

This study investigated the impact of sidedness of colorectal cancer (CRC) in elderly patients on the prognosis. In a sub-analysis of a multicenter case–control study of CRC patients who underwent surgery at ≥ 80 years old conducted in Japan between 2003 and 2007, both short- and long-term outcomes were compared between right-sided colon cancers (RCCs) and left-sided colorectal cancers (LCCs). RCCs were defined as those located from the cecum to the transverse colon. Among the 1680 patients who underwent curative surgery, 812 and 868 had RCCs and LCCs, respectively. RCCs were more frequent than LCCs in those who were female, had renal comorbidities, and had a history of abdominal surgery. Regarding tumor characteristics, RCCs were larger, invaded more deeply, and were diagnosed as either mucinous or signet ring-cell carcinoma more frequently than LCCs. Regarding the prognosis, patients with RCCs had a significantly longer cancer-specific survival (CS-S) and cancer-specific relapse-free survival (CS-RFS) than those with LCCs. Furthermore, sidedness was determined to be an independent prognostic factor for CS-S and CS-RFS. RCCs, which accounted for half of the cases in patients ≥ 80 years old, showed better long-term outcomes than LCCs.

Background: Recently, there has been a significant increase in the utilization of self-expandable metallic stents (SEMSs) for treating malignant colorectal obstructions through colorectal stenting. The mechanical properties of SEMSs are usually considered to affect clinical outcomes of patients with malignant colorectal obstructions. Methods: This single-arm, prospective, multicenter study of SEMS with a lower axial force and high axial force zero-border included 200 patients with malignant colorectal obstruction. Technical and clinical success, stent patency, and adverse events associated with SEMS placement were evaluated. Results: One patient was excluded, and 199 patients were evaluated. The treatment intent was bridge-to-surgery in 129 and palliation in 70 patients. Technical and clinical success rates were 99.5% and 97.0%, respectively. The percentage of the ColoRectal Obstruction Scoring System scores of 3 or higher improved significantly from 19.2% before placement to 93.9% after placement. Clinical success was not achieved in five patients due to insufficient stent expansion in four patients and stent occlusion in one patient. Only one patient underwent emergency surgery for perforation of the proximal colon, far from where the stent was placed; the rescue procedure was not performed, despite no improvement in proximal dilatation due to insufficient stent expansion. Among the palliation cohort, 15 patients received chemotherapy, including molecular-targeted agents such as bevacizumab. There were no fatal cases related to stent placement. Conclusions: For management of malignant colorectal obstruction, this newly developed SEMS with low axial force and a high axial force zero-border showed high technical and clinical success rates, and an extremely low perforation rate (0.5%).

Objectives: Endoscopic submucosal dissection (ESD) of colorectal lesions was invented in Japan, but postoperative management including hospital stay has not been reconsidered due to the Japanese insurance system. To explore appropriate postoperative management after colorectal ESD, we reviewed short-term outcomes after ESD in non-selected consecutive patients. Methods: Patients who underwent colorectal ESD from April 2013 to September 2020 in one institution were reviewed. The primary outcome measure was the occurrence of adverse events stratified by the Clavien-Dindo classification with five grades. A logistic regression model with the Firth procedure was applied to investigate predictors of severe (grade III or greater) adverse events. Results: A total of 330 patients (female 40%, male 60%; median 72 years; IQR 65-80 years) with colorectal lesions (median 30 mm, IQR 23-40 mm; colon 77%, rectum 23%; serrated lesion 4%, adenoma 47%, mucosal cancer 30%, invasive cancer 18%) was evaluated. The en bloc resection rate was 97%. The median dissection time was 58 min (IQR: 38-86). Intraprocedural perforation occurred in 3%, all successfully treated by endoscopic clipping. No delayed perforations occurred. Postprocedural bleeding occurred in 3% on days 1-10 (median day 2); all were controlled endoscopically. Severe adverse events included only delayed bleeding. In analyzing severe adverse events in a multivariate logistic regression model with the Firth procedure, antithrombotic agent use (p = 0.016) and rectal lesions (p = 0.0010) were both significant predictors. Conclusions: No serious adverse events occurred in this series. Four days of hospitalization may be too long for the majority of patients after ESD.

Objectives:Anastomotic leakage (AL) is a serious complication associated with morbidity, mortality, and poor prognosis. This study aimed to identify the risk factors and predictive biomarkers for AL after colorectal surgery with double stapling technique (DST) anastomosis.Methods:We retrospectively analyzed 331 patients who underwent elective colorectal cancer surgery with DST anastomosis between April 2012 and July 2021. Patient-, tumor-, and surgery-related variables were examined using univariate and multivariate analyses to identify the risk factors for AL. Postoperative inflammatory biomarkers were also analyzed to identify the predictive factors for AL.Results:AL occurred in 28 (8.5%) patients. In multivariate analysis, male sex, a history of diabetes mellitus and high ligation of inferior mesenteric artery (IMA) were significant risk factors for AL. Serum C-reactive protein (CRP) levels on postoperative day (POD) 3 and 7 were significantly correlated with AL (OR; 95% CI, 1.134; 1.044-1.232, p = 0.003, and 1.154; 1.036-1.286, p = 0.009, respectively). The cut-off value of CRP on POD 3 was 10.91 mg/dL (sensitivity 0.714, specificity 0.835, positive predictive value [PPV] 0.290, and negative predictive value [NPV] 0.969). The cut-off value of CRP on POD 7 was 4.58 mg/dL (sensitivity 0.821, specificity 0.872, PPV 0.377, and NPV 0.981).Conclusions:Male sex, a history of diabetes mellitus and high ligation of IMA were risk factors for AL in colorectal cancer surgery with DST anastomosis. The predictive biomarkers for cases without AL were CRP levels on POD 3 and 7.

Although cancer immunotherapy using immune checkpoint inhibitors (ICIs) has been recognized as one of the major treatment modalities for malignant diseases, the clinical outcome is not uniform in all cancer patients. Myeloid-derived suppressor cells (MDSCs) represent a heterogeneous population of immature myeloid cells that possess various strong immunosuppressive activities involving multiple immunocompetent cells that are significantly accumulated in patients who did not respond well to cancer immunotherapies. We reviewed the perspective of MDSCs with emerging evidence in this review. Many studies on MDSCs were performed in malignant diseases. Substantial studies on the participation of MDSCs on non-malignant diseases such as chronic infection and autoimmune diseases, and physiological roles in obesity, aging, pregnancy and neonates have yet to be reported. With the growing understanding of the roles of MDSCs, variable therapeutic strategies and agents targeting MDSCs are being investigated, some of which have been used in clinical trials. More studies are required in order to develop more effective strategies against MDSCs.

Anal canal cancer (ACC) has been reported to be an uncommon cancer in Japan, as in the USA, Europe, and Australia. This retrospective multi-institutional study was conducted to clarify the characteristics of ACC in Japan. First, the histological ACC type cases treated between 1991 and 2015 were collected. A detailed analysis of the characteristics of anal canal squamous cell carcinoma (SCC) cases was then conducted. The results of the histological types revealed that of the 1781 ACC cases, 435 cases (24.4%) including seven cases of adenosquamous cell carcinomas were SCC and 1260 cases (70.7%) were adenocarcinoma. However, the most common histological type reported in the USA, Europe, and Australia is SCC. Most ACC cases are adenocarcinomas and there is a low incidence of SCC in Japan which is different from the above-mentioned countries. Moreover, we reclassified T4 into the following two groups based on tumor size: T4a (tumor diameter of 5 cm or less) and T4b (tumor diameter of more than 5 cm). The results of the TNM classification of SCC revealed that the hazard ratio (HR) to T1 of T2, T3, T4a, and T4b was 2.45, 2.28, 2.89, and 4.97, respectively. As T4b cases had a worse prognosis than T4a cases, we propose that T4 for anal canal SCC in Japan be subclassified into T4a and T4b.

Background There are many reports on the choice of treatment for and prognosis of left-sided obstructive colorectal cancer; however, few studies have focused on the prognostic factors of left-sided obstructive colorectal cancer. Therefore, we analyzed the prognostic factors using a post hoc analysis of a retrospective multicenter study in Japan. Methods A total of 301 patients were enrolled in this study to investigate the prognostic factors for relapse-free survival. The relationships between sex, age, decompression for bridge to surgery, depth of invasion, lymph node metastasis, postoperative complications, adjuvant chemotherapy, carcinoembryonic antigen, carbohydrate antigen 19-9, neutrophil-to-lymphocyte ratio, and relapse-free survival were examined. Results No change in the decompression method, T3 cancer, negative postoperative complications (grades 0-1 of Clavien-Dindo classification), and adjuvant chemotherapy during Stage III indicated a significantly better prognosis in a Cox univariate analysis. Lymph node metastasis was not selected as a prognostic factor. Excluding patients with <12 harvested lymph nodes (possible stage migration), lymph node metastasis was determined as a prognostic factor. In a Cox multivariate analysis, change in the decompression method, depth of invasion, lymph node metastasis (excluding N0 cases with <12 harvested lymph nodes), and adjuvant chemotherapy were prognostic factors. Conclusions Similar to those in nonobstructive colorectal cancer, depth of invasion and lymph node metastasis were prognostic factors in left-sided obstructive colorectal cancer, and patients with <12 dissected lymph nodes experienced stage migration. Stage migration may result in disadvantages, such as not being able to receive adjuvant chemotherapy.

We evaluated the efficacy of neoadjuvant chemotherapy(NAC)for 38 patients with locally advanced rectal cancer (LARC). We administered mFOLFOX6 in 15, FOLFIRI in 3, CAPOX in 10, IRIS in 1 and FOLFOXIRI in 9 patients. We also used bevacizumab in 31 and panitumumab in 7 patients. There were 27 male and 11 female patients, with a median age of 64 years, and location was RS 2, Ra 9, Rb 21, and P 6. Synchronous distant metastasis was recognized in 13 patients. Nine patients had suffered adverse event of Grade 3, however all patients could complete NAC. Clinical response was CR 3, PR 31, SD 4, response rate was 91.9%, and reduction rate was 43.3(range 18.8-100)%. Clinical response of distant metastasis was CR 3, PR 9 and SD 1. Laparoscopic surgery was performed in 29 patients. Postoperative complications of Grade 2 of Clavien- Dindo classification were recognized in 14 and Grade 3 in 4 patients. Three- and five-year overall survival rate of 25 patients without distant metastasis were 79.6% and 74.9%, respectively; and 13 with distant metastasis were 61.6% and 52.6%, respectively. The efficacy, safety and postoperative outcomes of NAC for LARC are favorable, and we think that NAC will be one of the treatments for LARC.

A 74-year-old woman presented to her local physician with hematochezia. Colonoscopy showed a locally advanced 30 mm cancer adjacent to the anus. She refused abdominoperineal resection because of the necessity for a permanent stoma and decided to receive proton beam therapy (70.4 Gy equivalent) as an alternative treatment in another hospital. After proton beam therapy, the rectal cancer was eradicated at colonoscopy, and she was referred for surveillance. One year later, she developed frequent hematochezia. Colonoscopy revealed dilated vessels with oozing hemorrhage in the tumor scar. This was diagnosed as hemorrhagic radiation proctitis induced by proton beam therapy. Over 8 months, endoscopic hemostatic therapy was performed five times using argon plasma coagulation for refractory hemorrhagic disease. The patient’s hemoglobin level dropped to as low as 4.5 g/dl requiring blood transfusion. Thereafter, the radiation proctitis gradually improved and there is no evidence of recurrent tumor for over 10 years. To the best of our knowledge, there are no previous reports of proton beam therapy eradication of locally advanced rectal cancer. Clinicians should be aware that radiation-induced proctitis with refractory hemorrhage could develop.

Cold snare polypectomy is being increasingly adopted; however, there are few reports of cold snare polypectomy regarding antithrombotic therapy. This study aimed to investigate the real-world safety of cold snare polypectomy during antithrombotic therapy. We collected data from consecutive patients undergoing cold snare polypectomy in a single hospital between 2013 and 2017. Indications for cold snare polypectomy were any ≤ 10 mm polyp. The primary outcome was delayed bleeding. We compared rates of delayed bleeding between patients with and without antithrombotic therapy and analyzed risk factors for delayed bleeding using binary logistic regression model with firth procedure. In 2152 patients (mean age 67.6 years; male 1411), 4433 colorectal polyps (mean diameter 5.0 mm) underwent cold snare polypectomy. Clipping during the procedure was performed for 5.8%. Delayed bleeding occurred in 0.51% (11/2152) of patients and 0.25% (11/4433) of polyps, but no major delayed bleeding occurred. A total of 244 (11%) patients received antithrombotic therapy. Patients on antithrombotic therapy were older (p < 0.001), more likely male (p < 0.001) and had cold snare polypectomy in the proximal colon (p = 0.011). The rate of delayed bleeding was higher in patients on antithrombotic therapy (1.64% vs. non-antithrombotic therapy 0.37%, p = 0.009). Larger polyp size (> 5 mm), use of clips, and antithrombotic therapy were significant risk factors for delayed bleeding. There was no clear association between specific antithrombotic agents and delayed bleeding. Delayed bleeding after cold snare polypectomy was rare even in patients with antithrombotic therapy, and no major delayed bleeding occurred.

Small intestinal hemorrhage due to diverticulum is a relatively rare condition among gastrointestinal hemorrhages. We report a case of diverticular hemorrhage of the terminal ileum that was successfully treated by ultra-selective transcatheter arterial embolization using a triaxial system. A 25-year-old man was referred to our hospital due to melena. Abdominal contrast-enhanced computed tomography demonstrated marked extravasation of contrast medium in a diverticulum of the terminal ileum. We immediately attempted transcatheter arterial embolization after onset of hemorrhagic hypovolemic shock. Angiogram of the superior mesenteric artery revealed apparent hemorrhage at the end of the ileocolic artery. We performed embolization with 2 platinum coils using a triaxial system via the vasa recta of the terminal ileum. This procedure stopped extravasation of contrast medium. Postoperative course was uneventful, and he was discharged four days postoperatively. The triaxial system may facilitate high diagnostic ability to accurately identify target arteries of the ileal diverticular hemorrhage.

Aim: Increasing evidence indicates that a high Neutrophil-to-Lymphocyte Ratio (NLR) and Skeletal Muscle Mass (SMM) loss are associated with poor survival in patients with unresectable advanced/ metastatic Colorectal Cancer (uCRC). We assessed the clinical outcomes in uCRC patients receiving chemotherapy in relation to the NLR and SMM loss. Methods: In this study, we retrospectively enrolled 78 patients with uCRC who underwent systemic chemotherapy between December 2012 and June 2019. The bilateral psoas muscle crosssectional area at the superior border of the fourth lumbar vertebra was measured using Computed Tomography (CT), and the Psoas Muscle Index (PMI) was determined. SMM loss was defined as a decrease in PMI of ≥ 5% when comparing pre-chemotherapy PMI values with values obtained 3 months after chemotherapy initiation. The NLR was calculated as the absolute neutrophil count divided by the absolute lymphocyte count measured before chemotherapy. The NLR cutoff value was set as 3.0. Patients were divided into four groups according to NLR status and SMM loss: High NLR/SMM loss, high NLR/non-SMM loss, low NLR/SMM loss, and low NLR/non-SMM loss. Results: Thirty-two patients had a high NLR; they exhibited significantly shorter Overall Survival (OS) than those with a low NLR (median 16.0 vs. 30.3 months; log-rank, p=0.001). The OS in patients with high NLR/SMM loss was significantly lower than that in all other groups (median 11.8 vs. 21.5 vs. 21.5 vs. 34.2 months; log-rank, p<0.001). In multivariate analysis, high NLR/SMM loss was an independent prognostic factor for shorter OS (hazard ratio: 3.44, 95% confidence interval: 1.45 to 8.12, p=0.0048). Conclusion: There was a significant correlation between NLR status and SMM loss and prognosis in patients with uCRC who were receiving chemotherapy. Intensive supportive care, including exercise and nutrition, is needed for uCRC patients with a high NLR.

BACKGROUND:Computed tomography colonography (CTC) may be superior to colonoscopy and barium enema for detecting diverticula. However, few studies have used CTC to diagnose diverticula.AIM:To evaluate the current prevalence and distribution of colonic diverticula in Japan using CTC.METHODS:This study was conducted as part of the Japanese National Computed Tomographic Colonography Trial, which included 1181 participants from 14 hospitals in Japan. We analyzed the prevalence and distribution of colonic diverticula and their relationships with age and sex. The relationship between the diverticula and the length of the large intestine was also analyzed.RESULTS:Diverticulosis was present in 48.1% of the participants. The prevalence of diverticulosis was higher in the older participants (P < 0.001 for trend). The diverticula seen in younger participants were predominantly located in the right-sided colon. Older participants had a higher frequency of bilateral type (located in the right- and left-sided colon) diverticulosis (P < 0.001 for trend). The length of the large intestine with multiple diverticula in the sigmoid colon was significantly shorter in those without diverticula (P < 0.001).CONCLUSION:The prevalence of colonic diverticulosis in Japan is higher than that previously reported. The prevalence was higher, and the distribution tended to be bilateral in older participants.