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Abstract Aim The best bowel preparation method for rectal surgery remains controversial. In this study we compared the efficacy and safety of mechanical bowel preparation (MBP) alone and MOABP (MBP combined with oral antibiotic bowel preparation [OABP]) for rectal cancer surgery. Methods In this retrospective study we analyzed data from the Japanese Diagnosis Procedure Combination (DPC) database on 37 291 patients who had undergone low anterior resection for rectal cancer from 2014 to 2017. Propensity score matching analysis was used to compare postoperative outcomes between MBP alone and MOABP. Results A total of 37 291 patients were divided into four groups: MBP alone: 77.7%, no bowel preparation (NBP): 16.9%, MOABP: 4.7%, and OABP alone: 0.7%. In propensity score matching analysis with 1756 pairs, anastomotic leakage (4.84% vs 7.86%, P

Abstract Aim We aimed to evaluate the operative trends and compare the short‐term outcomes between open and laparoscopic surgery for congenital biliary dilatation (CBD) in adults using real‐world data from Japan. Methods Data from the Japanese Diagnosis Procedure Combination database on 941 patients undergoing surgery for CBD at 357 hospitals from April 1, 2016, to March 31, 2021, were analyzed. The patients were divided into two groups: open surgery (n = 764) and laparoscopic surgery (n = 177). We performed a retrospective analysis via a multilevel analysis of the short‐term surgical outcomes and costs between open and laparoscopic surgery. Results The rate of laparoscopic surgery has been increasing annually and had almost doubled to 25% by 2021. There were no significant differences in the in‐hospital mortality rate or postoperative morbidity between the two groups. The length of anesthesia was significantly longer in the laparoscopic than open surgery group (8.80 vs 6.16 hours, p

Juvenile polyposis syndrome (JPS) is a rare disease characterized by multiple hamartomatous polyps within the gastrointestinal tract. SMAD4 or BMPR1A is known as a causative gene of JPS. Approximately 75% of newly diagnosed cases have an autosomal-dominantly inherited condition, whereas 25% are sporadic without previous history of polyposis in the family pedigree. Some patients with JPS develop gastrointestinal lesions in childhood and require continuous medical care until adulthood. JPS is classified into three categories according to phenotypic features of polyp distributions, including generalized juvenile polyposis, juvenile polyposis coli, and juvenile polyposis of the stomach. Juvenile polyposis of the stomach is caused by germline pathogenic variants of SMAD4 with a high risk leading to gastric cancer. Pathogenic variants of SMAD4 are also associated with hereditary hemorrhagic telangiectasia-JPS complex, inducing regular cardiovascular survey. Despite growing concerns regarding the managing JPS in Japan, there are no practical guidelines. To address this situation, the guideline committee was organized by the Research Group on Rare and Intractable Diseases granted by the Ministry of Health, Labor and Welfare involving specialists from multiple academic societies. The present clinical guidelines explain the principles in the diagnosis and management of JPS with three clinical questions and corresponding recommendations based on a careful review of the evidence and involve incorporating the concept of the Grading of Recommendations, Assessment, Development, and Evaluation system. Herein, we present the clinical practice guidelines of JPS to promote seamless implementation of accurate diagnosis and appropriate management of pediatric, adolescent, and adult patients with JPS.

Abstract Aim Adhesive small bowel obstructions (SBO) are one of the most common complications following abdominal surgery, and they decrease patient quality of life. Since 2000, laparoscopic surgery has been employed with increasing frequency, as has adhesion prevention material (APM). In this study we tried to evaluate whether laparoscopic surgery and APM reduce the incidence of SBO. Methods In Cohort 1, we included patients who developed SBO and received inpatient treatment between 2015 and 2018. We evaluated the elapsed time between precedent surgery and the onset of SBO, and what kind of surgery most often causes SBO. In Cohort 2, we included patients who underwent digestive surgery between 2012 and 2014 and evaluated SBO incidence within 5 y after the precedent surgery. Results In all, 2058 patients were included in Cohort 1. Of these, 164 had experienced no precedent surgery. Among patients with a history of abdominal surgery, 29.7% experienced SBO within 1 y after the precedent surgery and 48.1% within 3 y. Altogether, 18798 patients were analyzed in Cohort 2. The incidence of SBO after laparoscopic colorectal surgery was lower than that of open colorectal surgery (P < .001), and laparoscopic gastroduodenal surgery was also lower (P = .02). However, there were no differences between laparoscopic and open surgery for other types of surgery. The use of APM had no effect on SBO incidence in any type of abdominal surgery. Conclusions Laparoscopic surgery helps to reduce SBO incidence only in colorectal surgery, and possibly in gastroduodenal surgery. APM does not reduce SBO after abdominal surgery.

Abstract 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.

Abstract Objectives Colonoscopy surveillance reduces the incidence of colorectal cancer through the detection and endoscopic removal of adenomas. Current guidelines recommend that patients with Lynch syndrome should have colonoscopy surveillance every 1–2 years starting at the age of 20–25. However, insufficient data are available to evaluate the quality and safety of colonoscopy surveillance for patients with Lynch syndrome nationwide in Japan. Methods Patients with Lynch syndrome (n = 309) from 13 institutions who underwent one or more colonoscopy procedures were enrolled in this retrospective analysis. Colonoscopy completion rate, colonoscopy‐related complication rate, proportion with an adequate colonoscopy interval, and adenoma detection rate were reviewed. Results The colonoscopy completion rate was 98.8% and a history of previous colorectal cancer surgery was significantly associated with a higher completion rate. All complications were associated with endoscopic treatment and the rate of bleeding needing hemostasis and perforation needing surgical repair were both 0.16% after colonoscopy with polypectomy. The adenoma detection rate at the first colonoscopy was 25%. Although there was no difference in the completion and complication rates based on differences in the colonoscopy experience of the endoscopist, the detection rate of adenomas and intramucosal cancers was significantly higher with more experienced endoscopists. The proportion of patients developing cancer was significantly higher with a >24 months than a ≤24 months interval. Conclusion High‐volume experienced endoscopists and appropriate surveillance intervals may minimize the risk of developing colorectal cancers in patients with Lynch syndrome.

Abstract Background Appendicitis is classified as either complicated (CA) or uncomplicated (UA). Some authors have shown that the epidemiologic trends of CA and UA may differ. The aim of this study was to clarify differences in backgrounds and surgical outcomes between CA and UA patients. Methods This study was a cohort study. We extracted case data from the Japanese Diagnosis Procedure Combination (DPC) database from January 2014 to December 2017. Patients were classified into three groups, depending on whether they underwent emergency appendectomy for CA (CA group), emergency appendectomy for UA (UA group), or elective appendectomy (EA group). We evaluated patient characteristics and surgical outcomes for each group. Results We included 89,355 adult patients in the study, comprising 29,331 CA, 48,691 UA, and 11,333 EA patients. Old age, larger body mass index, smoking, and medication with antidiabetic drugs, oral corticosteroids, oral antiplatelet drugs, and oral anticoagulant drugs were independent risk factors for CA. The percentage of CA increased with age. In‐hospital mortality (0.15%, 0.02%, and 0.00%) and 30‐d mortality (0.09%, 0.01%, and 0.00%), respectively, of CA patients were significantly higher than those of the UA and EA groups. The duration of postoperative antibiotic administration, duration of fasting, and time before removal of a prophylactic drain were significantly longer in the CA group than in the UA and EA groups. Conclusion Backgrounds and treatment outcomes of CA and UA patients after emergency surgery are entirely different. Thus, the treatment strategy of CA and UA patients should differ accordingly.

Background: Anti-epidermal growth factor receptor (EGFR) therapy has been identified to prolong the survival of metastatic colorectal cancer (mCRC) patients without RAS mutations. However, its efficacy is not always consistent for these patients. Genomic profiles of primary tumors and metastases are not always concordant; thus, chemotherapeutic agents can alter the tumor molecular profile. This molecular heterogeneity may explain resistance to anti-EGFR therapy. Liquid biopsy using circulating tumor DNA (ctDNA) is a novel, non-invasive diagnostic tool that can accommodate this molecular heterogeneity, providing a comprehensive, real-time view of the molecular landscape. In this study, we evaluated the predictive value of genomic mutations in ctDNA for primary and acquired resistance to anti-EGFR therapy. Methods/Design: This study is a prospective, multicenter, observational study of mCRC patients with wild-type tissue RAS treated with cytotoxic agents and anti-EGFR antibodies as first-line therapy. Genomic mutations, including RAS, BRAF, PIK3CA, and EGFR in ctDNA, are assessed via Droplet Digital PCR before starting chemotherapy and every 3 months thereafter until disease progression. The target sample size is estimated to be 100. The primary endpoint is the response rate in patients without RAS mutation in their blood sample before starting chemotherapy. Discussion: This study will clarify the predictive value of baseline RAS mutation in ctDNA for responses to anti-EGFR therapy; the frequency of emerging RAS, BRAF, PIK3CA, and EGFR mutations in ctDNA; and the association with secondary resistance to anti-EGFR therapy in first-line therapy for wild-type tissue RAS mCRC patients.

Background: Some studies have reported that adhesion prevention barriers (APBs) reduce adhesion after abdominal surgery; however, evidence showing that APBs reduce the incidence of postoperative small bowel obstruction (SBO), one of the most serious complications after abdominal surgery, is little. One concern is that APBs are usually applied only under the midline incision, although adhesion can occur at any place in the peritoneum where an incision is made during surgery. INTERCEED® is an APB that reportedly prevents postoperative SBO after surgery. This study aims to assess the clinical utility of INTERCEED® for the prevention of SBO after laparoscopic colorectal cancer surgery and determine whether the application site of INTERCEED® affects the incidence of SBO. Methods/Design: This study is a prospective, multicenter, observational study conducted in Japan. The primary end point is the incidence of postoperative SBO 2 years after laparoscopic colorectal cancer surgery. The secondary end points include whether the site of the application of INTERCEED® affects the incidence of SBO. Each surgeon selects one of the following three procedures: 1) INTERCEED® is placed only under the midline incision; 2) INTERCEED® is placed at the site of bowel mobilization and/or lymph node dissection, but not under the midline incision; and 3) INTERCEED® is placed at both sites. Discussion: This is the first study to assess whether the placement of APBs affects the incidence of SBO. The study results may lead to a subsequent randomized study.

Abstract Pancreatic ductal adenocarcinoma (PDAC) is characterised by dense desmoplasia and hypoxic microenvironment. Our previous reports demonstrated that hyaluronan (HA), especially low-molecular-weight HA, provides a favourable microenvironment for PDAC progression. However, the effect of hypoxia on HA metabolism remains unknown. Using quantitative real-time RT-PCR and western blot analysis, we analysed the changes in the expression of HA-synthesizing enzymes (HAS2 and HAS3) and HA-degrading enzymes (HYAL1, KIAA1199/CEMIP) in PDAC cell lines under hypoxic conditions. Hypoxia increased the mRNA and protein expression of KIAA1199, whereas it decreased HYAL1 expression. The expression of HAS3 was increased and HAS2 remained unchanged in response to hypoxia. The effect of KIAA1199 on hypoxia-induced cell migration was determined using a transwell migration assay and small-interfering RNA (siRNA). Hypoxia enhanced the migratory ability of PDAC cells, which was inhibited by KIAA1199 knockdown. We also used immunohistochemistry to analyse the protein expression of hypoxia inducible factor (HIF) 1α and KIAA1199 in PDAC tissues. There was a significant immunohistochemically positive correlation between KIAA1199 and HIF1α. These findings suggest that hypoxia-induced KIAA1199 expression may contribute to enhanced motility in PDAC.

Abstract Aim Appendicitis is divided into two categories: complicated appendicitis (CA) and uncomplicated appendicitis (UA). In pediatric patients with CA, the use of interval appendectomy (IA), which is non‐operative management followed by elective surgery, has decreased the number of postoperative complications. Before discussing the merit of IA for adult patients, we need to clarify whether the frequency and seriousness of the complication rate after emergency surgery is higher for CA than for UA. Methods This retrospective cohort study included adult patients who underwent appendectomy and who were registered in the National Clinical Database (NCD) from 2014 to 2016. Patients with CA who underwent emergency appendectomy comprised the CA group. Patients with UA comprised the UA group. Patients with chronic or recurrent appendicitis who underwent elective appendectomy comprised the elective appendectomy (EA) group. Primary outcomes were all morbidity, serious morbidity, and mortality within 30 days after appendectomy. Results We included 109 256 patients in the study: 14 798 CA, 86 876 UA, and 7582 EA patients. Compared with the UA group, the rates of all morbidity, serious morbidity, and mortality were significantly higher in the CA group. All morbidity, serious morbidity, and mortality rates were significantly lower in the EA group than in the other two groups. Conclusions We confirmed that emergency surgery for CA places the patient at relatively higher risk. We also showed that the risk associated with EA is significantly lower than that for the other methods.

Abstract Background Metastasis of renal cell carcinoma (RCC) to the gallbladder is rare, and its clinicopathological feature remains poorly understood. We here present two cases of gallbladder metastasis from RCC presenting as a hypervascular polypoid lesion. Case presentation The first case was a 73-year-old man who had undergone right nephrectomy for clear cell RCC. Imaging studies detected a hypervascular polypoid lesion in the gallbladder 6 years after nephrectomy. Laparoscopic cholecystectomy was done. The pathological findings of the polypoid lesion showed proliferation of clear cells in the submucosal layer. Immunohistochemically, the tumor was positive for carbonic anhydrase 9 (CA9) but negative for cytokeratin 7 (CK7), suggestive of metastatic RCC. The second case was a 43-year-old man who had undergone right nephrectomy for clear cell RCC. Imaging studies revealed a hypervascular polypoid lesion of 20 mm in diameter in the gallbladder 1 year after nephrectomy. The patient underwent expanded cholecystectomy and extra-hepatic bile duct resection with lymphadenectomy. Microscopically, the polypoid lesion of the gallbladder was composed of clear cells in the submucosal layer. Immunohistochemical analysis showed positive staining for epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA) but negative staining for CK7, leading to the diagnosis of metastatic RCC. Conclusions Gallbladder metastasis from RCC is rare but should be considered when a hypervascular polypoid lesion in the gallbladder is detected during the follow-up period after RCC treatment.

Abstract Invasive cribriform carcinoma is a rare type of invasive breast carcinoma, and a few cases have been reported. Its features are a cribriform pattern resembling the histological structures of cribriform ductal carcinoma in situ and an excellent prognosis. However, the extent of progress for intraductal extension must be carefully evaluated.

Background: Treatment with TAS-102 has significantly improved the progression-free survival (PFS) and overall survival (OS) of patients with metastatic colorectal cancer (mCRC). Reportedly, the combination of TAS-102 plus bevacizumab extends the median PFS. The present study aimed to confirm the efficacy and safety of TAS-102 plus bevacizumab (biweekly administration) as third-line chemotherapy for patients with mCRC. Methods/Design: This is a single-arm, open-label, prospective, nonrandomized, multicenter phase II trial conducted in Japan. With a threshold and expected PFS of 2.1 and 3.5 months, respectively, the simulation results showed a sample size of 42 with α = 0.05 (both sides) for 90% power, based on the One-Arm Binomial test using the SWOG statistical tool. If the estimated dropout is 7%-8%, the target sample size is estimated to be 45. The TAS-CC4 study regimen comprised 28-day cycles with biweekly oral administration of TAS-102 (35 mg/m2 twice daily on days 1-5 and 15-19 of every 28-day cycle) and bevacizumab (5.0 mg/kg on days 1 and 15). The primary end point is the PFS; secondary end points include response rate (RR), OS, grade 3 neutropenia, and genetic alterations (KRAS/BRAF mutations) in the circulating cell-free DNA. Discussion: The present study can contribute to the determination of the effective dosing interval of TAS-102 and bevacizumab in patients with mCRC and is thought to lead to prophylaxis of neutropenia and prolongation of the treatment period.

Summary: Background: Although the laparoscopic approach reduces pain associated with abdominal surgery, postoperative pain remains a problem. Ultrasound-guided rectus sheath block and transversus abdominis plane block have become increasingly popular means of providing analgesia for laparoscopic surgery. Methods: Ninety patients were enrolled in this study. A laparoscopic puncture needle was inserted via the port, and levobupivacaine was injected into the correct plane through the peritoneum. The patients' postoperative pain intensity was assessed using a numeric rating scale. The effects of laparoscopic nerve block versus percutaneous anesthesia were compared. Results: This novel form of transperitoneal anesthesia did not jeopardize completion of the operative procedures. The percutaneous approach required more time for performance of the procedure than the transperitoneal technique. Conclusion: This new analgesia technique can become an optional postoperative treatment regimen for various laparoscopic abdominal surgeries. What we mainly want to suggest is that the transperitoneal approach has the advantage of a higher completion rate. A percutaneous technique is sometimes difficult with patients who have severe obesity and/or coagulation disorders. Additional studies are required to evaluate its benefits. Keywords: colorectal surgery, nerve block, postoperative pain, rectus sheath block, transversus abdominis plane block

Anal canal duplication (ACD) is a rare congenital malformation, usually detected early in life. We report a case of a 67-year-old female with symptomatic ACD associated with a presacral cyst. Physical examination revealed an accessory opening located in the midline, posterior to the true anus. Imaging examinations, including fistulography, endoanal ultrasonography, and magnetic resonance imaging, revealed a blind-ending fistulous tract without connecting with the rectum and a presacral cyst posterior to the rectum. Complete surgical excision of the tract with cyst was performed through a posterior sagittal approach. Histologic examination revealed squamous epithelium lining and smooth muscle bundles, thereby confirming ACD. The postoperative course was uneventful, and the patient was doing well; no recurrence was observed 4 years after surgery. ACD can present for the first time in infants, children, and adults. Imaging examinations are useful for the diagnosis and preoperative assessment of ACD. Therefore, ACD should be considered in the differential diagnosis, even in adults, when a posterior perineal orifice is encountered, particularly in female patients. Once ACD is suspected, intense imaging inspection is recommended to visualize the ACD and associated anomalies, and surgical removal is warranted to prevent inflammatory complications or malignant changes.

Mucinous adenocarcinoma arising in chronic fistula-in-ano is rare, and diagnosing it at an early stage is difficult. The role of endoanal ultrasonography in diagnosing the condition has not been discussed in the study. Herein, we report three cases of mucinous adenocarcinoma arising from anal fistulas in which endosonography played an important role in diagnosing malignant change. Three male patients with a 5- to 20-year history of anal fistula were referred to our hospital due to perianal induration, progressive anal pain, or mucopurulent secretion. In all three patients, endosonography revealed a multiloculated complex echoic mass with isoechoic solid components communicating with a trans-sphincteric fistula and sonography-guided biopsy under anesthesia revealed mucinous adenocarcinoma. All patients underwent abdominoperineal resection with lymph node dissection. One patient with a local recurrence died 3 years after surgery and two have remained disease-free for >6 years. These observations suggest that endosonography may be a reliable technique for the diagnosis of mucinous adenocarcinoma arising from chronic fistula-in-ano. Sonography-guided biopsy is useful for the definitive diagnosis of malignancy. Therefore, periodic endosonography assessment should be recommended for patients with persistent anal fistula, especially those with progressive clinical symptoms. Once malignancy is suspected, aggressive sonography-guided biopsy under anesthesia should be performed, which may enable an early diagnosis, curative treatment, and favorable long-term results.

Progression of cancer is often associated with interactions between cancer cells and extracellular matrix (ECM) surrounding them. Increasing evidence has suggested that accumulation of hyaluronan (HA), a major component of ECM, provides a favorable microenvironment for cancer progression. Pancreatic ductal adenocarcinoma (PDAC) is characterized typically by a dense desmoplastic stroma with a large amount of HA, making this molecule as an attractive target for therapy. Several studies have shown efficacy of inhibitors of HA synthesis or signaling for the treatment of PDAC. Recent studies have also demonstrated substantial improvements in the effects of chemotherapy by a targeted depletion of stromal HA in PDAC using an enzymatic agent. Thus, targeting HA has been recognized as a promising therapeutic strategy to treat this highly aggressive neoplasm. In this review article, we summarize our current understanding of the role of HA in the progression of PDAC and discuss possible therapeutic approaches targeting HA.

We herein present a surgically treated case of huge adrenal myelolipoma. A 62-year-old woman presented to our surgical outpatient clinic with a retroperitoneal tumor. A clinical examination revealed an elastic soft, smooth-surfaced, painless, child-head-sized tumor with poor mobility, which was located in the left upper abdomen. Computed tomography (CT) and magnetic resonance imaging (MRI) of the abdomen revealed an uneven tumor surrounding the stomach, spleen, pancreas, and left kidney, which was 20 × 18 × 10 cm in size. The retroperitoneal tumor was resected. The tumor was attached to the surrounding organs, including the pancreas, spleen, and left kidney, but had not directly invaded these organs. The tumor was yellow and elastic soft and covered with a thin film. The origin of the tumor was suggested to be the left adrenal gland. The weight of the excised tumor was 1500 g. The histopathological diagnosis was adrenal myelolipoma. The patient had an uneventful recovery and was discharged from the hospital on the thirteenth day after the operation. She has been followed up in our outpatient clinic.

Tubulocystic carcinoma of the bile duct is extremely rare and has not been reported in the literature. We reported a case of cystic neoplasm of the liver with distinct histopathological features that could not be clearly classified as of either mucinous or intraductal papillary neoplasm. A 68-year-old Japanese patient had a multicystic biliary tumor within the liver. This tumor was detected on follow-up of polymyalgia rheumatica. The exophytic, multicystic, 35 × 50 mm mass was composed of complex tubulocystic structures. We initially suspected cystadenocarcinoma of the liver and performed radical operation. However, pathology ultimately showed it to be very rare tubulocystic carcinoma that derived from the bile duct. We reviewed the literature and describe the process of our differential diagnosis.

This report presents an operative case of advanced descending colon cancer in an adult patient with intestinal malrotation. A 63-year-old Japanese male was suffering from left side abdominal pain, abdominal distension, and constipation. An endoscopic examination revealed an advanced tumor in the descending colon. Computed tomography (CT) of the abdomen revealed the thickening of the descending colon wall and superior mesenteric vein rotation. An opaque enema detected severe stenosis of the descending colon. An abdominal X-ray examination revealed the dilation of the colon and small intestine with niveau. At the insertion of an ileus tube, the C-loop of the duodenum was observed to be absent and the small intestine was located on the right side of the abdomen. After the decompression of the bowel contents, laparotomy was performed. Descending colon cancer was observed to have directly invaded the left side of the transverse colon. Left hemicolectomy, lymph node dissection, and appendectomy were performed. The patient had an uneventful recovery and was discharged from the hospital on the 16th day after surgery. This report presents a rare operative case of descending colon cancer in an adult patient with intestinal malrotation.

An 83-year-old Japanese man was admitted to our hospital for gastric adenocarcinoma mimicking a submucosal tumor in the gastric body. Considering his general condition, partial resection of the stomach and dissection of regional lymph nodes were performed; a dome-shaped tumor that was largely covered by normal mucosa and having a shallow central stellate ulcer was removed. Histopathologically, the carcinoma cell nests were surrounded by prominent lymphoid stroma. Sarcoid-like epithelioid granulomas were noted both in the tumor stroma and in the regional lymph node with metastasis. Epstein-Barr virus (EBV)-encoded RNA (EBER) in situ hybridization showed an intense and diffuse positive reaction in the carcinoma cells and no reaction in the surrounding gastric and lymphoid tissues. While the presence of lymphoid stroma is a characteristic finding in EBV-associated lymphoepithelioma-like carcinoma, sarcoid-like epithelioid granulomas might be associated with latent EBV infection.

Objective: This study aimed to evaluate the effect of continuing preoperative aspirin monotherapy on surgical outcomes in patients receiving antiplatelet therapy (APT). Background: The effectiveness of continuing preoperative aspirin monotherapy in patients undergoing APT in preventing thromboembolic consequences is mostly unknown. Methods: This prospective multicenter cohort study on the Safety and Feasibility of Gastroenterological Surgery in Patients Undergoing Antithrombotic Therapy (GSATT study) conducted at 14 clinical centers enrolled and screened patients between October 2019 and December 2021. The participants (n= 1170) were assigned to the continued-APT group, discontinued-APT group, or non-APT group, and the surgical outcomes of each group were compared. Propensity score matching performed between the continued and discontinued-APT groups to investigate the effect of continuing preoperative aspirin therapy on thromboembolic complications. Results: The rate of thromboembolic complications in the continued- APT group was substantially lower than that in the non-APT or discontinued- APT groups (0.5% vs 2.6% vs. 2.9%; P=0.027). Multivariate investigation of the entire cohort revealed that discontinuation of APT (P< 0.001) and chronic anticoagulant use (P<0.001) were independent risk factors for postoperative thromboembolism. The post-matching evaluation demonstrated that the rates of thromboembolic complications were significantly different between the continued and discontinued-APT groups (0.6% vs 3.3%; P=0.012). Conclusions: APT discontinuation after elective gastroenterological surgery increases the risk of thromboembolic consequences, whereas continuing preoperative aspirin greatly reduces this risk. The continuation of preoperative aspirin therapy in APT-received patients is considered one of the best alternatives for preventing thromboembolism during elective gastroenterological surgery. [ABSTRACT FROM AUTHOR]