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The training of trainees to perform endoscopies is challenging. There is no standardized training program in Korea. Trainees usually learn to perform endoscopies under the supervision of an educator, an expert endoscopist. However, most of educators have never received formal training. For high quality and effecting training, formal training program for educators is needed. Also, specific assessment tools measuring performance and improving training are required. The use of simulators for acquiring, maintaining, and assessing skills in endoscopy has grown over the past decade. Many data suggest that simulation training may accelerate the acquisition of specific technical skills in endoscopy early in training. If we include education using simulators in basic endoscopy education, it will be of great help to shorten the endoscopy training time and improve the endoscopy training environment. A significant portion of medical lawsuits against gastroenterologists in Korea are related to complications related to sedation. Therefore, endoscopy education should include contents related to sedation education. Also, systematic and thorough education program along with assessment tool measuring true competence of sedation in endoscopy is needed. Changes should be made at all levels to improve our endoscopy training system.

Introduction: KRAS, BRAF, and DNA mismatch repair (MMR) mutations aid clinical decision-making for colorectal cancer (CRC) patients. To ensure accurate predictions, the prognostic utilities of these biomarkers and their combinations must be individualized for patients with various TNM stages. Methods: Here, we retrospectively analyzed the clinicopathological features of 904 Korean CRC patients who underwent CRC surgery in three teaching hospitals from 2011 to 2013; we also assessed the prognostic utilities of KRAS, BRAF, and MMR mutations in these patients. Results: The overall frequencies of KRAS and BRAF mutations were 35.8% and 3.2%, respectively. Sixty-nine patients (7.6%) lacking expression of ≥1 MMR protein were considered MMR protein deficient (MMR-D); the remaining patients were considered MMR protein intact. KRAS mutations constituted an independent risk factor for shorter overall survival (OS) in TNM stage I–IV and stage III patients. BRAF mutations were associated with shorter OS in TNM stage I–IV patients. MMR-D status was strongly positive prognostic in TNM stage I–II patients. Discussion/Conclusion: To our knowledge, this is the first multicenter study to explore the prognostic utilities of KRAS, BRAF, and MMR statuses in Korean CRC patients. Various combinations of KRAS, BRAF, and DNA MMR mutations serve as genetic signatures that affect tumor behavior; they are prognostic in CRC patients.

Supplementary Figure legends; Supplementary Materials and Methods: Detailed and expanded methods on cell lines, in-vitro assays, in-vivo tumor model, histology, and tumor specimens for all data presented.

Generation and characterization of villin-KITENIN/APCmin/+ mice.

Purpose and Experimental Design: The molecular events in the malignant progression of colon adenoma after loss of adenomatous polyposis coli (APC) are not fully understood. KITENIN (KAI1 C-terminal interacting tetraspanin) increases the invasiveness of colorectal cancer cells, and we identified a novel EGFR-independent oncogenic signal of EGF that works under coexpressed KITENIN and ErbB4. Here we tested whether elevated KITENIN and ErbB4 contribute to further progression of intestinal adenoma following APC loss.Results: The intestinal tissues of villin-KITENIN transgenic mice in which villin-driven KITENIN expression induces increased c-Jun expression exhibit mild epithelial cell proliferation but no epithelial lineage changes compared with those of nontransgenic mice. Among the four ErbB4 isoforms, JM-a/CYT-2 and JM-b/CYT-2 exhibited the highest AP-1 activity when cells coexpressing KITENIN and each isoform were stimulated by EGF. Interestingly, predominant overexpression of the ErB4-CYT-2 mRNA as well as increased EGFR expression were observed in intestinal adenoma of APCmin/+ mice, which makes the microenvironment of activated EGF signaling. When we crossed villin-KITENIN mice with APCmin/+ mice, intestinal tumor tissues in the crossed mice showed the characteristics of early-stage invading adenocarcinoma. In patients with colorectal cancer, ErbB4-CYT-2 mRNA expression was significantly greater in tumor tissues than in normal adjacent tissues, but no significant differences in tumor tissue expression were found between different colorectal cancer stages. Furthermore, the mRNA expression of KITENIN and that of ErbB4-CYT-2 were positively correlated in human colorectal cancer tissue.Conclusions: Elevated coexpression of KITENIN and ErbB4-CYT-2 promotes the transition of colon adenoma to adenocarcinoma within an APC loss–associated tumor microenvironment. Clin Cancer Res; 22(5); 1284–94. ©2015 AACR.

Characterization of intestinal epithelial tissues from non-TG and KIT-TG mice.

Schematic showing the underlying mechanism of KITENIN/ErbB4-CYT-2 in colon tumor progression.

Effects of elevated KITENIN on cell proliferation and anoikis of intestinal epithelial cells.

Generation of villin-KITENIN transgenic (KIT-TG) mice.

Increased expression of ErbB4-CYT-2, but not ErbB4-CYT-1, isoform in human CRC mucosa.

Immunohistochemical analyses of nontumor intestinal tissues from the APCmin/+ mouse and the compound KIT-TG/APCmin/+ mouse.

Purpose: This study aimed to determine the correlation between protein induced by vitamin K absence or antagonist-II (PIVKA-II) and stereotactic body radiotherapy (SBRT) in patients with hepatocellular carcinoma (HCC). Materials and Methods: Sixty-one patients received SBRT between 2015 and 2020 with a median dose of 48 Gy (range, 39 to 60 Gy) with a median of 4 fractions. Changes in tumor markers before and after SBRT were analyzed. Results: The median follow-up period was 31 months (range, 12 to 64 months). The estimated 2-year in-field failure-free survival, progression-free survival (PFS), and overall survival rates were 82.0%, 39.3%, and 96.7%, respectively. Patients with decreased PIVKA-II levels through SBRT had significantly few in-field failures (p = 0.005). Patients with PIVKA-II levels of ≤25 mAU/mL after SBRT had significantly long PFS (p = 0.004). Conclusion: PIVKA-II could be a useful surrogate marker for response or survival outcomes in patients with localized HCC receiving SBRT.

The prospective Crohn's Disease Clinical Network and Cohort Study is a nationwide multicenter cohort study of patients with Crohn's disease (CD) in Korea, aiming to prospectively investigate the clinical features and long-term prognosis associated with CD.Patients diagnosed with CD between January 2009 and September 2019 were prospectively enrolled. They were divided into two cohorts according to the year of diagnosis: cohort 1 (diagnosed between 2009 and 2011) versus cohort 2 (between 2012 and 2019).A total of 1,175 patients were included, and the median follow-up duration was 68 months (interquartile range, 39.0 to 91.0 months). The treatment-free durations for thiopurines (p0.001) and anti-tumor necrosis factor agents (p=0.018) of cohort 2 were shorter than those of cohort 1. Among 887 patients with B1 behavior at diagnosis, 149 patients (16.8%) progressed to either B2 or B3 behavior during follow-up. Early use of thiopurine was associated with a reduced risk of behavioral progression (adjusted hazard ratio [aHR], 0.69; 95% confidence interval [CI], 0.50 to 0.90), and family history of inflammatory bowel disease was associated with an increased risk of behavioral progression (aHR, 2.29; 95% CI, 1.16 to 4.50). One hundred forty-one patients (12.0%) underwent intestinal resection, and the intestinal resection-free survival time was significantly longer in cohort 2 than in cohort 1 (p=0.003). The early use of thiopurines (aHR, 0.35; 95% CI, 0.23 to 0.51) was independently associated with a reduced risk of intestinal resection.The prognosis of CD in Korea appears to have improved over time, as evidenced by the decreasing intestinal resection rate. Early use of thiopurines was associated with an improved prognosis represented by a reduced risk of intestinal resection.

A 54-year-old man was transferred from another hospital due to a hematoma in the third portion of the duodenum on abdomen CT. He had been admitted for 2 weeks due to vomiting at another hospital. He had abdominal discomfort and nausea without abdominal pain when he visited the Gwangyang Sarang Hospital. Other than a distended abdomen and mild general abdominal tenderness, the results of physical examination were unremarkable. Abdominal CT revealed an approximately 9 cm thick walled hematoma at the anteroinferior site of the duodenal third portion. Upper endoscopy revealed stenosis of the third portion of the duodenum without mucosal lesions. The endoscope was not advanced through the narrowed duodenal lumen. A retroperitoneal hematoma was diagnosed, and his state was classified as subacute rather than acute based on the duration. The surgeon did not recommend surgical treatment. Urgent treatment was unnecessary; he was managed conservatively. The size of the hematoma decreased from 9.0 cm to 5.8 cm on the following CT. He could begin to eat food on the 26th admission day, and he was discharged on the 31st admission day. The hematoma disappeared entirely on the following CT. This paper describes a rare case of idiopathic retroperitoneal hematoma with a spontaneous resolution.

Pelvic radiation therapy (RT) is a common treatment for malignancies, including gynecological, genitourinary, and lower gastrointestinal tract cancers. However, chronic radiation proctitis (RP) is an unavoidable side effect, and its clinical presentation varies from asymptomatic to potentially life-threatening. This study evaluated the clinical characteristics and risk factors of chronic RP.Patients with chronic RP (212) following RT for various pelvic cancers between January 2015 and December 2021 were enrolled. Clinical characteristics of RP were analyzed retrospectively. Severity was graded according to the Radiation Therapy Oncology Group (RTOG) modified rectal toxicity score and Vienna rectoscopy score (VRS), and risk factors were statistically analyzed.The most common pelvic cancer observed was cervical cancer. The patients received three-dimensional conformal RT (3D-CRT), intensity-modulated RT, or a combination of 3D-CRT and intracavitary RT (ICR). Rectal bleeding occurred in 70 (33.0%) patients. Previous abdominopelvic surgery and total radiation dose significantly correlated with the RTOG score and VRS. Previous abdominopelvic surgery, ICR, and total radiation dose were associated with chronic hemorrhagic RP. All patients with chronic hemorrhagic RP were treated with argon plasma coagulation (APC). 91.4% of cases required 1-3 APC sessions to resolve the bleeding, with a mean of 1.7 sessions.Our results showed that previous abdominopelvic surgery and total radiation dose were significant risk factors related to chronic RP, while total radiation dose was related to chronic hemorrhagic RP. We also showed that APC was effective and safe for chronic hemorrhagic RP.

Engulfment and cell motility 1 (ELMO1) plays a crucial role in the process of migration, chemotaxis, and metastasis of tumor cells. ELMO1 has been implicated in the pathogenesis of various cancers. However, the distinct function of ELMO1 in colorectal cancer (CRC) is unclear. We determined whether ELMO1 affects the oncogenic behavior of CRC cells and investigated its prognostic value in CRC patients.We investigated the impact of ELMO1 on tumor cell behavior using small interference RNA (siRNA) in CRC cell lines, including SW480 and DLD1. The expression of ELMO1 was investigated by reverse transcription-polymerase chain reaction (RT-PCR), immunohistochemistry, and enzyme-linked immunosorbent assay (ELISA) in cancer tissues and sera obtained from CRC patients.ELMO1 knockdown suppressed tumor cell proliferation in SW480 and DLD1 cells. ELMO1 knockdown-induced apoptosis through up-regulation of caspase-3, -7, and PARP activities and down-regulation of the anti-apoptotic Mcl-1 protein. ELMO1 knockdown-induced cell-cycle arrest by decreasing cyclin D1, cyclin-dependent kinase 2, 4 and 6, and the 25C cell division cycle (CDC25C). ELMO1 knockdown suppressed tumor cell invasion and migration. The expression of E-cadherin was increased, while that of Vimentin and Claudin 1 decreased following ELMO1 knockdown. The phosphorylation levels of PDK1, Akt, and GSK-3β and were down-regulated after ELMO1 knockdown. The expression of ELMO1 was found up-regulated in cancer tissues and sera taken from CRC patients. ELMO1 expression was significantly associated with tumor stage, lymph node metastasis, distant metastases, and poor survival.ELMO1 mediates tumor progression by increasing tumor cell motility and inhibiting apoptosis in human CRC.

Background/Aims: High-quality colonoscopy is essential to reduce colorectal cancer-related deaths. Little is known about colonoscopy quality in non-academic practice settings. We aimed to evaluate the quality of colonoscopies performed in community hospitals and nonhospital facilities. Methods: Colonoscopy data were collected from patients referred to six tertiary care centers after receiving colonoscopies at community hospitals and nonhospi tal facilities. Based on their photographs, we measured quality indicators includ ing cecal intubation rate, withdrawal time, adequacy of bowel preparation, and number of polyps. Results: Data from a total of 1,064 colonoscopies were analyzed. The overall ce cal intubation rate was 93.1%. The median withdrawal time was 8.3 minutes, but 31.3% of colonoscopies were withdrawn within 6 minutes. Community hospitals had longer withdrawal time and more polyps than nonhospital facilities (median withdrawal time: 9.9 minutes vs. 7.5 minutes, p < 0.001; mean number of polyps: 3.1 vs. 2.3, p = 0.001). Board-certified endoscopists had a higher rate of cecal intu bation than non-board-certified endoscopists (93.2% vs. 85.2%, p = 0.006). A total of 819 follow-up colonoscopies were performed at referral centers with a median interval of 28 days. In total, 2,546 polyps were detected at baseline, and 1,088 were newly identified (polyp miss rate, 29.9%). Multivariable analysis revealed that old er age (odds ratio [OR], 1.032; 95% confidence interval [CI], 1.020 to 1.044) and male sex (OR, 1.719; 95% CI, 1.281 to 2.308) were associated with increased risk of missed polyps. Conclusions: The quality of colonoscopies performed in community hospitals and nonhospital facilities was suboptimal. Systematic reporting, auditing, and feedback are needed for quality improvement.

Mucosa-associated lymphoid tissue (MALT) lymphoma predominantly involves the gastrointestinal tract, with the stomach being the most commonly affected site. Colonic involvement is quite rare. Hence, the etiology, clinical characteristics, treatment, and outcome of colonic MALT lymphoma are not well established. This paper reports a case of MALT lymphoma of the transverse colon, presenting as a subepithelial tumor in a 50-year-old woman. The patient received 3,060 cGy in 17 fractions with external beam radiation therapy for three weeks. At 2 months after radiation therapy, a colonoscopy examination revealed complete resolution and a scar change of the lesion. The follow-up at 24 months revealed no evidence of tumor recurrence after radiation therapy.

Background: Engulfment and cell motility 1 (ELMO1) plays a crucial role in the process of migration, chemotaxis, and metastasis of tumor cells. ELMO 1 has been implicated in the pathogenesis of various cancers. However, the distinct function of ELMO1 in colorectal cancer (CRC) is unclear. We determined whether ELMO1 affected the oncogenic behavior of CRC cells and investigated its prognostic value in CRC patients. Methods: We investigated the impact of ELMO1 on tumor cell behaviors using small interference RNA in CRC cell lines, including SW480 and DLD1. The expression of ELMO1 was investigated by reverse transcription-polymerase chain reaction, immunohistochemistry, and enzyme-linked immunosorbent assay in cancer tissues and sera taken from CRC patients. Results: ELMO1 knockdown suppressed tumor cell proliferation in SW480 and DLD1 cells. ELMO1 knockdown-induced apoptosis through up-regulation of caspase-3, -7, and PARP activities and down-regulation of the anti-apoptotic Mcl-1 protein. ELMO1 knockdown-induced cell cycle arrest by decreasing cyclin D1, cyclin-dependent kinase 2, 4 and 6, and the 25C cell division cycle (CDC25C). ELMO1 knockdown suppressed tumor cell invasion and migration. The expression of E-cadherin was increased, and Vimentin and Claudin 1 decreased with ELMO1 knockdown. The phosphorylation levels of PDK1, Akt, and GSK-3β and were down-regulated by ELMO1 knockdown. The expression of ELMO1 was up-regulated in cancer tissues and sera taken from CRC patients. ELMO1 expression was significantly associated with tumor stage, lymph node metastasis, distant metastases, and poor survival. Conclusions: These results indicate that ELMO1 mediates tumor progression by increasing tumor cell motility and inhibiting apoptosis in human CRC.

CD47 is an immunoregulatory protein that is found on the cell surface and plays significant roles in cellular functions such as proliferation, apoptosis, migration, and immune homeostasis. CD47 is overexpressed in various human cancers and is associated with tumor development, progression, and poor prognosis. In this study, we analyzed the expression of CD47 to determine whether it affected the oncogenic behavior of colorectal cancer (CRC) and investigated the prognostic value of CD47 expression in patients with CRC. We investigated 468 patients with CRC who underwent curative surgery and examined the expression of CD47 in tumor and lymph node tissues by performing RT-PCR and immunohistochemistry. Apoptosis, proliferation, angiogenesis, and lymphangiogenesis were determined via a TUNEL assay and immunohistochemical staining for Ki-67, CD34, and D2-40. CD47 expression was increased in human CRC tumors and metastatic lymph nodes compared with normal colorectal mucosa and non-metastatic lymph node tissues. CD47 expression was significantly associated with perineural invasion, lymphovascular invasion, cell differentiation, cancer stage, depth of invasion, lymph node metastasis, distant metastasis, and poor survival. The mean apoptotic index and microvessel density value of CD47-positive tumors were significantly higher than those of CD47-negative tumors. However, no significant difference was observed between CD47 expression and Ki-67 labeling index or lymphatic vessel density. These results indicate that CD47 mediated the progression of CRC by inducing tumor cell apoptosis and angiogenesis.

Rationale: Rectal inflammatory myofibroblastic tumor (IMT) is an extremely rare mesenchymal tumor characterized by a mixture of spindle-shaped myofibroblasts or fibroblasts and inflammatory infiltration of lymphocytes and plasma cells. To date, only 8 cases of rectal IMT have been reported. Herein, we report an additional case of rectal IMT in a 28-year-old woman. Patient concerns: A 28-year-old woman presented with abdominal pain and hematochezia. Diagnoses: Colonoscopy showed a 3.0-cm subepithelial tumor with central ulceration, covered by white exudate in the rectum. Rectal magnetic resonance imaging revealed a 4.0 × 3.0-cm-sized well-defined subepithelial tumor in the right wall of the rectum, with suspicious right perirectal fat infiltration. Interventions: Laparoscopic anterior resection was performed. Microscopic examination of the surgical specimen revealed bland-looking spindle cells intermingled with lymphoplasma cells. Immunohistochemistry and fluorescence in situ hybridization showed anaplastic lymphoma kinase positivity and anaplastic lymphoma kinase positivity rearrangement. Rectal IMT was confirmed based on histological, immunohistochemical, and fluorescence in situ hybridization findings. The patient was doing well without evidence of tumor recurrence 1 year after the surgery. Lessons: Rectal IMT, despite its rarity, should be considered in the differential diagnosis of rectal cancer. Second, an accurate histopathologic diagnosis and complete surgical resection can be the most important approaches to offer a chance for the cure of rectal IMT.

Background/aims This study compared the efficacy, compliance, and safety of bowel preparation between sodium picosulfate with magnesium citrate (SPMC) and oral sulfate solution (OSS). Methods A prospective randomized multicenter study was performed. Split preparation methods were performed in both groups; the SPMC group, 2 sachets on the day before, and 1 sachet on the day of the procedure, the OSS group, half of the OSS with 1 L of water on both the day before and the day of the procedure. The adenoma detection rate (ADR), adequacy of bowel preparation using the Boston Bowel Preparation Scale (BBPS) score, patient satisfaction on a visual analog scale (VAS), and safety were compared between the 2 groups. Results This study analyzed 229 patients (121 in the SPMC group and 108 in the OSS group). ADR showed no differences between 2 groups (51.7% vs. 41.7%, P> 0.05). The mean total BBPS score (7.95 vs. 8.11, P> 0.05) and adequate bowel preparation rate (94.9% vs. 96.3%, P> 0.05) were similar between the 2 groups. The mean VAS score for taste (7.62 vs. 6.87, P=0.006) was significantly higher in the SPMC group than in the OSS group. There were no significant differences in any other safety variables between the 2 groups except nausea symptom (36.1% vs. 20.3%, P=0.008). Conclusions Bowel preparation for colonoscopy using low volume OSS and SPMC yielded similar ADRs and levels of efficacy. SPMC had higher levels of satisfaction for taste and feeling than did OSS.

Background/Aims: The use of a low-volume bowel cleansing agent is associated with a greater willingness to undergo repeat colonoscopy. Oral sulfate solution (OSS) is a recently approved low-volume agent; however, its efficacy and safety in the elderly population remain unclear. We aimed to evaluate the efficacy, safety, and acceptability of the OSS preparation, in comparison to those of a standard polyethylene glycol (PEG; 4 L) preparation, in elderly patients. Methods: A multicenter, randomized, investigator-blinded study was conducted. Participants were randomized to receive OSS or 4-L PEG with a split-dose regimen. Bowel cleansing efficacy was assessed using the Boston Bowel Preparation Scale (BBPS). Acceptance, satisfaction, and preparation-related symptoms were recorded. Additionally, blood parameters were analyzed for electrolyte abnormalities and nephrotoxicity. Results: A total of 193 patients were analyzed. No group differences in overall bowel cleansing efficacy were observed, with “adequate” preparations achieved in 95.9% (93/97) and 94.8% (91/96) of patients in the OSS and 4L PEG groups, respectively (p=0.747). However, mean BBPS scores for the entire (p=0.010) and right colon (p=0.001) were significantly higher in the OSS group than in the 4-L PEG group. The severity of clinical adverse events and frequency of acute kidney injury were similarly low, and no clinically meaningful electrolyte changes were identified. Self-reported scores regarding amount (p

Appropriate colonoscopy withdrawal times for individual colonic segments are not well known. The relationship between withdrawal time and adenoma detection rate (ADR)/polyp detection rate (PDR) in individual colonic segments was examined in this study.This was a prospective observational study involving 724 patients who underwent colonoscopy screening or surveillance colonoscopy from October 2015 to February 2017 at 10 university hospitals.In the right side of the colon, the ADR (33.2% vs 13.7%, P .001), PDR, serrated polyp detection rate, and number of adenomas per colonoscopy (APC) were significantly higher when the colonoscopy withdrawal time was ≥2 minutes compared with 2 minutes. When the withdrawal time was ≥4 minutes in the proximal colon and ≥3 minutes in the left segment of the colon, the ADR, PDR, and APC were significantly higher compared with withdrawal times of 4 minutes and 3 minutes, respectively. Multivariate analyses showed that the ADR was significantly associated with withdrawal times of ≥2 minutes in the right side of the colon (odds ratio [OR], 2.98; 95% confidence interval [CI], 1.72-5.15; P .001), ≥4 minutes in the proximal colon (OR, 4.48; 95% CI, 3.15-6.36; P .001), and ≥3 minutes in the left segment of the colon (OR, 2.92; 95% CI, 1.74-4.91; P .001).The PDR and ADR appeared to be significantly increased when the withdrawal time was ≥2 minutes in the right-sided colon segment, ≥4 minutes in the proximal colon, and ≥3 minutes in the left-sided colon segment compared with shorter withdrawal times.

Sessile serrated adenomas/polyps (SSA/Ps) are precancerous lesions that account for one-third of colorectal cancers. The endoscopic and pathologic differentiation between SSA/Ps without dysplasia (SSA/POs) and SSA/Ps with dysplasia or adenocarcinoma (SSA/PDAs) can be difficult. This study aimed to assess the clinical characteristics of SSA/PDs. This multicenter retrospective cohort study included 532 patients who underwent endoscopic resection and were pathologically diagnosed with SSA/POs and SSA/PDAs. Initially, medical, endoscopic, and histopathological records of patients who underwent endoscopic resection of SSA/POs and SSA/PDAs at eight university hospitals in Korea between January 2005 and December 2015 were reviewed. A total of 307 (57.7%) patients were detected in men and 319 (60.0%) were located in the proximal colon. Most SSA/Ps had a flat, slightly elevated, or sessile morphology. The most prevalent endoscopic findings of SSA/Ps were nodular surface (244, 45.9%), disrupted vascular pattern (232, 43.6%), altered fold contour (141, 26.5%), dome-shaped morphology (135, 25.4%), and pale color (115, 21.6%). SSA/POs were more commonly found in the proximal colon, compared to SSA/PDAs. SSA/PDAs displayed 0-Ip, Isp, IIb or IIa + IIc morphologies more frequently, while SSA/POs displayed 0-Is or IIa morphology more frequently. The frequency of a rim of debris/bubbles was significantly higher in SSA/POs, while nodular surface and disrupted vascular pattern were significantly higher in SSA/PDAs. In the univariate analysis of endoscopic features, SSA/PDAs were significantly associated with the distal colon location, 0-Isp and IIb morphologies, nodular surface, and disrupted vascular pattern. In the multivariate analysis, 0-IIb, nodular surface, and disrupted vascular pattern were significantly associated with SSA/PDAs. SSA/Ps with 0-IIb morphology, nodular surface and disrupted vascular pattern are associated with an increased risk of dysplasia or adenocarcinoma.

Self-expandable metal stent (SEMS) placement is commonly used for palliation of left-sided malignant colorectal obstruction (MCO). However, right-sided MCO is usually treated surgically. Recent studies that compared palliative SEMS insertion and emergency surgery in right-sided MCOs have reported conflicting results. This study aimed to compare the effectiveness of palliative SEMS placement in left-sided MCOs and right-sided MCOs and to investigate the predictive factors for clinical success and risk factors for complications. Data from 469 patients who underwent palliative SEMS placement for MCO at 6 hospitals in the Honam province of South Korea between 2009 and 2018 were reviewed. Among them, 69 patients with right-sided MCO and 400 patients with left-sided MCO who underwent SEMS placement for palliative purposes were enrolled. Clinical success, overall survival, complications, and predictive factors for clinical success and risk factors for complications were included as the main outcome measures. The clinical success rates were 97.1% (65/67) in right-sided MCO patients and 88.2% (353/400) in left-sided MCO patients. Complications including stent migration, tumor ingrowth, outgrowth, perforation, bacteremia/fever, and bleeding occurred in 10.1% (7/69) of right-sided MCO patients and 19.9% (79/400) of left-sided MCO patients. The mean overall survival of right-sided MCO was 28.02 months and 18.23 months for left-sided MCO. In multivariate logistic regression analysis, T3 stage tumors and the use of uncovered stents were significant factors for the clinical success of SEMS. The use of covered stents and performance status score of 0 to 2 were independent significant risk factors for complications. Palliative SEMS placement in right-sided MCO showed better clinical success rates than left-sided MCO. The use of uncovered stents is recommended for higher clinical success rates and lower complication rates.