Comparison of decompression tubes with metallic stents for the management of right-sided malignant colonic obstruction

BACKGROUND Emergency surgical resection is a standard treatment for right-sided malignant colonic obstruction; however, the procedure is associated with high rates of mortality and morbidity. Although a bridge to surgery can be created to obviate the need for emergency surgery, its effects on long-term outcomes and the most practical management strategies for right-sided malignant colonic obstruction remain unclear.AIM To determine the appropriate management approach for right-sided malignant colonic obstruction.METHODS Forty patients with right-sided malignant colonic obstruction who underwent curative resection from January 2007 to April 2017 were included in the study.We compared the perioperative and long-term outcomes of patients who received bridges to surgery established using decompression tubes and those created using self-expandable metallic stents(SEMS). The primary outcome was the overall survival duration(OS) and the secondary endpoints were the diseasefree survival(DFS) duration and the preoperative and postoperative morbidity rates. Analysis was performed on an intention-to-treat basis.RESULTS There were 21 patients in the decompression tube group and 19 in the SEMS group. There were no significant differences in the perioperative morbidity rates of the two groups. The OS rate was significantly higher in the decompression tube group than in the SEMS group(5-year OS rate; decompression tube 79.5%,SEMS 32%, P = 0.043). Multivariate analysis revealed that the bridge to surgery using a decompression tube was significantly associated with the OS(hazard ratio, 17.41; P = 0.004). The 3-year DFS rate was significantly higher in thedecompression tube group than in the SEMS group(68.9% vs 45.9%; log-rank test,P = 0.032). A propensity score–adjusted analysis also demonstrated that the prognosis was significantly better in the decompression tube group than in the SEMS group.CONCLUSION The bridge to surgery using trans-nasal and trans-anal decompression tubes for right-sided malignant colonic obstruction is safe and may improve long-term outcomes.

En bloc pancreaticoduodenectomy and right hemicolectomy for locally advanced right-sided colon cancer

AIM To assess the usefulness of en bloc right hemicolectomy with pancreaticoduodenectomy(RHCPD) for locally advanced right-sided colon cancer(LARCC).METHODS We retrospectively reviewed the database of Saitama Medical Center, Jichi Medical University, between January 2009 and December 2016. During this time, 299 patients underwent radical right hemicolectomy for right-sided colon cancer. Among them, 5 underwent RHCPD for LARCC with tumor infiltration to adjacent organs. Preoperative computed tomography(CT) was routinely performed to evaluate local tumor infiltration into adjacent organs. During the operation, we evaluated the resectability and the amount of infiltration into the adjacent organs without dissecting the adherent organs from the cancer. When we confirmed that radical resection was feasible and could lead to R0 resection, we performed RHCPD. The clinical data were carefully reviewed, and the demographic variables, intraoperative data, and postoperative parameters were recorded.RESULTS The median age of the 5 patients who underwent RHCPD for LARCC was 70 years. The tumors were located in the ascending colon(three patients) and transverse colon(two patients). Preoperative CT revealed infiltration of the tumor into the duodenum in all patients, the pancreas in four patients, the superior mesenteric vein(SMV) in two patients, and tumor thrombosis in the SMV in one patient. We performed RHCPD plus SMV resection in three patients. Major postoperative complications occurred in 3 patients(60%) as pancreatic fistula(grade B and grade C, according to International Study Group on Pancreatic Fistula Definition) and delayed gastric empty. None of the patients died during their hospital stay. A histological examination confirmed malignant infiltration into the duodenum and/or pancreas in 4 patients(80%), and no patients showed any malignant infiltration into the SMV. Two patients were histologically confirmed to have tumor thrombosis in the SMV. All of the tumors had clear resection margins(R0). The median follow-up time was 77 mo. During this period, two patients with tumor thrombosis died from liver metastasis. The overall survival rates were 80% at 1 year and 60% at 5 years. All patients with node-negative status(n = 2) survived for more than seven years.CONCLUSION This study showed that the long-term survival is possible for patients with LARCC if RHCPD is performed successfully, particularly in those with node-negative status.

Bowel function and quality of life after minimally invasive colectomy with D3 lymphadenectomy for right-sided colon adenocarcinoma

BACKGROUND Changes in bowel function after right-sided colectomy are not well understood compared to those associated with left-sided colectomy or rectal resection.In particular,there are concerns about bowel function after right-sided colectomy with complete mesocolic excision,which has become popular in the West.AIM To evaluate the functional outcomes of patients who underwent right-sided colectomy with D3 lymphadenectomy for colon cancer.METHODS Functional data from patients who underwent minimally invasive right-sided colectomy for colon cancer from October 2017 to September 2018 were prospectively collected.Functional outcomes were evaluated preoperatively and at 3,6,12,and 18 mo postoperatively.RESULTS Prior to surgery,57 patients answered the questionnaire,and 47 responded at three months,52 at 6 mo,52 at 12 mo,and 25 at 18 mo postoperatively.Most scales of quality of life and bowel function improved significantly over time.Urgency persisted to a high degree throughout the period without a significant change over time.The use of medications for defecation was about 10%over the entire period.Gas(P=0.023)and fecal frequency(P<0.001)increased,and bowel dysfunction group(P=0.028)was more common among patients taking medication.At six months,resected bowel and colon lengths were significantly different as a risk factor between the dysfunction group and the no dysfunction group[odd ratio(OR):1.095,P=0.026;OR:1.147,P=0.031,respectively]in univariate analysis,but not in multivariate analysis.CONCLUSION Despite D3 lymphadenectomy,most bowel symptoms improved over time after right-sided colectomy using a minimally invasive approach,and continuous medication was needed in only approximately 10%of patients.

Carcinoma located in a right-sided sigmoid colon:A case report

BACKGROUND A right-sided sigmoid colon is an extremely rare anatomic variation that should be considered as a possibility by surgeons and radiologists before surgery.Here,we report the first clinical case of a carcinoma in a right-sided sigmoid colon revealed by a preoperative computed tomography(CT).CASE SUMMARY A 56-year-old Chinese man was admitted to the hospital with abdominal pain.CT revealed a redundant sigmoid colon with a mass on the right side of the cecum and ascending colon.Laparoscopy confirmed an abnormal course in the descending colon and sigmoid colon.Subsequently,hemicolectomy was performed in an open manner after laparoscopic exploration.Pathological examination revealed an infiltrative mucinous adenocarcinoma with two lymph node metastases.The patient was discharged without any complications after a week.There were no signs of recurrence or metastasis during the 3-month followup period.CONCLUSION We report a rare anomaly of a right-sided sigmoid colon with carcinoma,which should be differentiated from ascending colon cancer and pericecal hernia to prevent errors and other surgical complications.

A Comparative Study of the Short-Term Efficacy of Laparoscopic Radical Resection of Right-Sided Colon Cancer with Two Different Surgeon Positions and Trocar Placements

Objective: To investigate the short-term efficacy of laparoscopic radical resection of right-sided colon cancer with two different surgeon positions and trocar placements. Methods: The data of 78 patients who underwent laparoscopic radical resection of right-sided colon cancer between January 2018 and August 2019 were retrospectively analysed. The surgical method was selected by the patients. The patients were divided into two groups according to the surgeons’ positioning habits and trocar placements. The group with the lead surgeon standing between the patient’s legs had 35 patients, and the group with the lead surgeon standing at the left side of the patient had 43 patients. The operation time, intraoperative blood loss, postoperative anal gas evacuation time, postoperative urinary catheter indwelling time, postoperative hospital stay, C-reactive protein (CRP) level on the first day after surgery, and postoperative pathological data and complications were compared between the two groups. Results: All patients underwent the laparoscopic radical resection of right-sided colon cancer, none converting to laparotomy. No significant difference (P > 0.05) in intraoperative blood loss (57.6 ± 21.3 ml vs 60.2 ± 35.3 ml), postoperative anal gas evacuation time (3.5 ± 1.1 d vs 3.8 ± 1.3 d), postoperative urinary catheter indwelling time (2.6 ± 1.3 d vs 2.4 ± 1.2 d), postoperative hospital stay (7.1 ± 1.8 d vs 7.5 ± 2.1 d), or CRP level on the first day after surgery (54.7 ± 9.6 mg/L vs 53.9 ± 8.2 mg/L) was detected between the two groups. The operation time was shorter in the group with the lead surgeon standing between the patient’s legs (185.2 ± 25.6 min vs 196.2 ±19.7 min) (P < 0.05). The two groups did not differ significantly in the tumour length (4.2 ± 1.3 cm vs 3.9 ± 1.5 cm), number of dissected lymph nodes (27.5 ± 11.6 vs 25.1 ± 15.4), pathological type, or postoperative pathological tumour-node-metastasis stage (P > 0.05). No patients died or had anastomotic fistula during their postoperative hospital stay, and the incidence of postoperative complications did not differ between the two groups (22.9% (8/35) vs 23.3% (10/42);P > 0.05). Conclusion: Under the principle of radical resection, the surgeon should adopt the most suitable standing position and trocar placement according to the specific situation. If the surgeon stands between the patient’s legs, this might shorten the operation time and promote a smoother surgery.

HSP27:a candidate differentially expressed protein between left-and right-sided colon carcinomas

Objective:The aim of the study was to screen differentially expressed proteins between left-and right-sided colon cancers by proteomics techniques and provide molecular genetic basis for oncobiological difference between left-and rightsided colon cancers.Methods:Tissue samples including left-and right-sided colon cancers were collected and preserved in the-80 ℃ refrigeratory.In the first part of our experiment,protein separating was performed by using two-dimensional gel electrophoresis(2-DE) and the images of the gels were acquired by the scanner and then analyzed to find the differentially expression protein-spots in different groups.The peptide mass fingerprintings(PMF) was acquired by matrix assisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF-MS) and the proteins were identified by data searching in the Mascot-database.Differentially expression proteins were assayed by RT-PCR,Western blot,and immunohistochemical methods.Results:The 55 differentially expressed protein spots were screened and 23 spots of them were identified.Compared to right-sided colon cancer,15 proteins up-regulated and 8 proteins down-regulated including HSP27 in left-sided colon cancer.HSP27 expressed higher in right-sided than in left-sided colon cancers by RT-PCR,Western blot and immunohistochemical methods.Conclusion:There were differentially expressed proteins between left-and right-sided colon cancers,especially differences in HSP27 expression in mRNA and protein level,which were molecular genetic basis for oncobiological difference between left-and right-sided colon cancers.

Analysis of 72 patients with colorectal high-grade neuroendocrine neoplasms from three Chinese hospitals

BACKGROUND Colorectal high-grade neuroendocrine neoplasms(HGNENs)are rare and constitute less than 1%of all colorectal malignancies.Based on their morphological differentiation and proliferation identity,these neoplasms present heterogeneous clinicopathologic features.Opinions regarding treatment strategies for and improvement of the clinical outcomes of these patients remain controversial.AIM To delineate the clinicopathologic features of and explore the prognostic factors for this rare malignancy.METHODS This observational study reviewed the data of 72 consecutive patients with colorectal HGNENs from three Chinese hospitals between 2000 and 2019.The clinicopathologic characteristics and follow-up data were carefully collected from their medical records,outpatient reexaminations,and telephone interviews.A survival analysis was conducted to evaluate their outcomes and to identify the prognostic factors for this disease.RESULTS According to the latest recommendations for the classification and nomenclature of colorectal HGNENs,61(84.7%)patients in our cohort had poorly differentiated neoplasms,which were categorized as high-grade neuroendocrine carcinomas(HGNECs),and the remaining 11(15.3%)patients had well differentiated neoplasms,which were categorized as high-grade neuroendocrine tumors(HGNETs).Most of the neoplasms(63.9%)were located at the rectum.More than half of the patients(51.4%)presented with distant metastasis at the date of diagnosis.All patients were followed for a median duration of 15.5 mo.In the entire cohort,the median survival time was 31 mo,and the 3-year and 5-year survival rates were 44.3%and 36.3%,respectively.Both the univariate and multivariate analyses demonstrated that increasing age,HGNEC type,and distant metastasis were risk factors for poor clinical outcomes.CONCLUSION Colorectal HGNENs are rare and aggressive malignancies with poor clinical outcomes.However,patients with younger age,good morphological differentiation,and without metastatic disease can have a relatively favorable prognosis.

Perivascular epithelioid cell neoplasm of the colon

A 17-year-old female presented with rectal bleeding from an ulcerated sigmoid mass in 1994.Initial pathological evaluation revealed a rare clear cell neoplasm of the colon,possibly originating from kidneys,adrenals,lung or a gynecologic source as a metastatic lesion.Extensive imaging studies were negative,and over the next 15 years,she remained well with no recurrence.The original resected neoplasm was reviewed and reclassified as a perivascular epithelioid cell neoplasm (PEComa).Although the long-term natural history of PEComas requires definition,increased clinical and pathological awareness should lead to increased recognition of an apparently rare type of colonic neoplasm that likely occurs more often than is currently appreciated.

Incidence of colorectal neoplasms among male pilots

AIM: To assess the prevalence of colorectal neoplasms (adenomas, advanced adenomas and colorectal cancers) among Israeli military and commercial airline pilots.

Pan-immune-inflammation value as a prognostic biomarker for colon cancer and its variation by primary tumor location

BACKGROUND A growing body of research indicates significant differences between left-sided colon cancers(LCC)and right-sided colon cancers(RCC).Pan-immune-inflammation value(PIV)is a systemic immune response marker that can predict the prognosis of patients with colon cancer.However,the specific distinction between PIV of LCC and RCC remains unclear.AIM To investigate the prognostic and clinical significance of PIV in LCC and RCC patients.METHODS This multicenter retrospective cohort study included 1510 patients with colon cancer,comprising 801 with LCC and 709 with RCC.We used generalized lifting regression analysis to evaluate the relative impact of PIV on disease-free survival(DFS)in these patients.Kaplan-Meier analysis,as well as univariate and multivariate analyses,were used to examine the risk factors for DFS.The correlation between PIV and the clinical characteristics was statistically analyzed in these patients.RESULTS A total of 1510 patients{872 female patients(58%);median age 63 years[interquartile ranges(IQR):54-71];patients with LCC 801(53%);median follow-up 44.17 months(IQR 29.67-62.32)}were identified.PIV was significantly higher in patients with RCC[median(IQR):214.34(121.78-386.72)vs 175.87(111.92-286.84),P<0.001].After propensity score matching,no difference in PIV was observed between patients with LCC and RCC[median(IQR):182.42(111.88-297.65)vs 189.45(109.44-316.02);P=0.987].PIV thresholds for DFS were 227.84 in LCC and 145.99 in RCC.High PIV(>227.84)was associated with worse DFS in LCC[PIV-high:Adjusted hazard ratio(aHR)=2.39;95%confidence interval:1.70-3.38;P<0.001]but not in RCC(PIV-high:aHR=0.72;95%confidence interval:0.48-1.08;P=0.114).CONCLUSION These findings suggest that PIV may predict recurrence in patients with LCC but not RCC,underscoring the importance of tumor location when using PIV as a colon cancer biomarker.

Malignant myopericytoma originating from the colon: A case report

BACKGROUND Myopericytoma is a benign tumor that typically occurs within subcutaneous tissue and most often involves the distal extremities,followed by the proximal extremities,neck,thoracic vertebrae and oral cavity.Complete resection is often curative.Malignant myopericytoma is extremely rare and has a poor prognosis.Here,we report for the first time a case of malignant myopericytoma originating from the colon.CASE SUMMARY A 69-year-old male was admitted to our hospital with right upper quadrant pain for five days.Imaging suggested a liver mass with hemorrhage.A malignant hepatic tumor was the initial diagnosis.Surgical resection was performed after a complete preoperative work up.Initial postoperative pathology suggested that the mass was a malignant myoblastoma unrelated to the liver.Four months after the first surgery,an enhanced computed tomography(CT)scan revealed a recurrence of the tumor.The diagnosis of malignant myopericytoma derived from the colon was confirmed on histopathological examination of the specimen from the second surgery.The patient did not return to the hospital regularly for surveillance.The first postoperative abdominal CT examination six months after the second surgery demonstrated multiple liver metastases.Survival time between the diagnosis of the tumor to death was approximately one year.CONCLUSION Malignant myopericytoma is a rare cancer.Preoperative diagnosis may be difficult.Due to a lack of treatment options,prognosis is poor.

Unexpected right-sided sigmoid colon in laparoscopy: A case report and review of literature

BACKGROUND The presence of a right-sided sigmoid colon is a rare anatomical variation usually discovered incidentally during surgical interventions.This case report details an unexpected right-sided sigmoid colon identified during a laparoscopic appendectomy and examines the pertinent literature to explore its clinical importance.CASE SUMMARY A 71-year-old woman presented with acute appendicitis.A preoperative computed tomography(CT)scan showed peri-appendiceal inflammation but no significant anatomical abnormalities.During laparoscopic surgery,an unexpected finding was encountered:The sigmoid colon was situated on the right side and exhibited an abnormal relationship with the cecum and ascending colon.Postoperative pathological examination confirmed appendicitis with no additional pathological findings.The right-sided sigmoid colon anomaly was verified through intraoperative assessment and later re-evaluation with CT and colonographic imaging.The patient underwent a laparoscopic appendectomy and experienced a smooth postoperative recovery.CONCLUSION This case highlights the necessity of being attentive to anatomical variations during laparoscopic surgery,particularly when managing appendicitis.A review of the literature indicated that the occurrence of a right-sided sigmoid colon is infrequent and may be associated with anomalies in midgut rotation during embryonic development.Awareness of this variation can help prevent surgical complications and inform future clinical practice.

Inhibitory effect of sulindac against chemically induced primary colonic tumours by N methyl N nitrosourea in mice

AIM To investigate the chemopreventive effect of sulindac, one of the nonstroidal anti inflammatory drugs (NSAIDs), on the growth of N methyl N nitrosourea (MNU) induced mouse colonic tumors.

Prevention of metastasis to liver by using 5-FU intraperitoneal chemotherapy in nude mice inoculated with human colonic cancer cells

AIMS Using a new approach of regional adjuvant chemotherapy to prevent cancer cells hepatic metasta- sis after radical surgery of large bowel cancer. METHODS A model of liver with metastasis of hu- man colonic cancer (HCC) cells in nude mice was used to observe the effect in prevention of metastasis of HCC cells inoculated via spleen applied with early postoper- ative intraperitoneal (IP) chemotherapy using large dose of 5-FU. RESULTS The incidence of metastasis to liver was decreased by 40%,the mean number of metastatic liv- er nodules in each animal was reduced by 50.89% and the mean survival times of each animal was prolonged by 48.21% by using 5-FU 40 mg/NS 40 ml/kg IP for two consecutive days as compared with the controls. CONCLUSIONS IP is a new and more effective re- gional adjuvant chemotheraputic approach in the pre- vention of liver metastasis HCC cells after radical surgery of large bowel cancer.

Patterns of lymph node metastasis are different in colon and rectal carcinomas

AIM:To describe patterns of lymph node metastasis in invasive colon and rectal carcinomas.METHODS:Clinical data of 2340 patients with colorectal carcinoma(stageⅠ to Ⅲ) who received radical resection,was retrospectively reviewed.Of the 2340 patients,1314 patients suffered from rectal carcinoma and 1026 from colon carcinoma.Patients with rectal cancer who received neoadjuvant chemoradiation therapy were excluded.Statistical analysis was performed using MannWhitney,χ 2 and Cochran's and Mantel-Haenszel tests(SPSS 15.0).A two-tailed P < 0.05 was considered statistically significant.RESULTS:Lymph node retrieval in the rectal carcinoma group was significantly lower than that in the colon carcinoma group(P < 0.001),while positive lymph node retrieval in the rectal carcinoma group was significantly higher than that in the colon carcinoma group(P < 0.001).The proportion of lymph node positive(N+) cases was higher(patients with one or more positive lymph nodes) in the rectal carcinoma group(P = 0.004).The number of N+ cases was compared at different T stages(T1-T4) to eliminate background bias and the results were confirmed(P < 0.001).In addition,the lymph node ratio(the ratio of number of positive lymph nodes over the number of lymph nodes examined) of stage Ⅲ cases in the rectal carcinoma group was significantly higher than that in the colon carcinoma group(P < 0.001).CONCLUSION:Rectal carcinomas seem more prone to metastasize to the lymph nodes than colon carcinomas,which may be of potential clinical significance.

Tumor growth inhibition effect of hIL-6 on colon cancer cells transfected with the target gene by retroviral vector

AIM To observe the tumor inhibitory effects bytransfecting IL-6 cDNA into colon cancer cell lineHT-29 with retroviral vector pZIP cDNA.METHODS Human IL-6 gene was reconstructedin retrovirus vector and transfected into incasingcells PA317 by lipofectamine mediated method,the clones of the cells transferred with hlL-6were selected by G418,and targeted HT-29 cellswere infected with the virus granules secretedfrom PA317 and also selected by G418.Test genetranscription and expression level byhybridization,ELISA and MTT assay,etc.Analyze tumor inhibitory effects according to thecell growth curve,plating forming rate andtumorigenicity in nude mice.RESULT Successfully constructed andtransfected recombinant expressing vectorspZIPIL-6 cDNA and got positive transfected celllines.The colon cancer cell line(HT-29 IL-5)transfected with the hlL-5 gene by retroviralvector was established.The log proliferationperiod and the doubling time of this cell line wasbetween 4 to 7 days and 2.5 days according tothe direct cell count,the cell proliferation wasobviously inhibited with MTT assay,the platinginhibitory rate was 50% by plating efficiencytest.When HT-29 IL-6 cells were inoculated intothe nude mice subcutaneously,carcinogenicactivity of the solid tumor was found superior tothe control group and the size of tumor was notsignificantly enlarged.Injection of combinationvirus fluid containing 11.-6 gene intotransplantation tumors could inhibit the growthand development of the tumor.CONCLUSION IL-6 could inhibit the growth andproliferation of colon cancer cells by retroviralvector-mediated transduction.

Malignant schwannoma of the pancreas involving transversal colon treated with en-bloc resection

Pancreatic schwannoma is a very uncommon tumor of the pancreas,with only 27 cases reported.Most pancreatic schwannomas are benign,with only four malignant tumors reported.We describe a case of giant malignant schwannoma of the pancreatic body and tail,which involved the transverse colon.The tumor was treated successfully with en bloc distal splenopancreatectomy and colon resection.This is believed to be the first reported radical operation for malignant schwannoma of the pancreatic body,with infiltration of the transverse colon,with excellent longterm results.The patient is alive and well 28 mo after the operation.The authors conclude that pancreatic schwannomas should be considered in the differential diagnosis of cystic neoplasms of the pancreas,although the diagnosis can only be confirmed by microscopic examination.In the case of the benign tumors,local excision is adequate,but in the case of malignant schwannoma,oncological standards must be fulfilled.

Inhibitory effect of modified citrus pectin on liver metastases in a mouse colon cancer model

AIM: To discuss the expression of glactin-3 in liver metastasis of colon cancer and its inhibition by modi- fied citrus pectin (MCP) in mice. METHODS: Seventy-five Balb/c mice were randomly di- vided into negative control group (n = 15), positive con- trol group (n = 15), low MCP concentration group (n = 15), middle MCP concentration group (n = 15) and high MCP concentration group (n = 15). CT26 colon cancer cells were injected into the subcapsule of mouse spleen in positive control group, low, middle and high MCP concentrations groups, except in negative control, to set up a colon cancer liver metastasis model. The concen- tration of MCP in drinking water was 0.0%, 0.0%, 1.0%, 2.5% and 5.0% (wt/vol), respectively. Liver metastasis of colon cancer was observed after 3 wk. Enzyme-linked immunosorbent assay (ELISA) was used to detect the concentration of galectin-3 in serum. Expression of ga- lectin-3 in liver metastasis was detected by immunohis- tochemistry. RESULTS: Except for the negative group, the percent- age of liver metastasis in the other 4 groups was 100%, 80%, 73.3% and 60%, respectively. The number of liver metastases in high MCP concentration group was significantly less than that in positive control group (P = 0.008). Except for the negative group, the median volume of implanted spleen tumor in the other 4 groups was 1.51 cm3, 0.93 cm3, 0.77 cm3 and 0.70 cm3, respec- tively. The volume of implanted tumor in middle and high MCP concentration groups was significantly smaller than that in positive control group (P = 0.019; P = 0.003). The concentration of serum galectin-3 in positive control and MCP treatment groups was significantly higher than that in the negative control group. However, there was no significant difference between them. Except for the negative control group, the expression of galectin-3 in liver metastases of the other 4 groups showed no sig- nificant difference. CONCLUSION: Expression of galetin-3 increases sig- nificantly in liver metastasis of colon cancer, which can be effectively inhibited by MCP.

Efficacy of cap-assisted colonoscopy according to lesion location and endoscopist training level

AIM: To evaluate the efficacy of cap-assisted colonoscopy(CAC) for detection of colorectal polyps and adenomas according to the lesion location and endoscopist training level.METHODS: Patients 20 years or older, who underwent their first screening colonoscopy in a single tertiary center from May 2011 to December 2012 were enrolled in this study. All patients underwent either CAC or standard colonoscopy(SC), and all of the procedures were performed by 11 endoscopists(8 trainees and 3 experts). All procedures were performed with highdefinition colonoscopes and narrow band imaging. The eight trainees had experiences of performing 150 to 500 colonoscopies, and the three experts had experiences of performing more than 3000 colonoscopies. A 4-mmlong transparent cap was attached to the end of a colonoscope in the CAC group. We retrospectively evaluated the number of polyps and adenomas, polyp detection rate(PDR), and the number of adenomas and adenoma detection rate(ADR) according to the lesion location and endoscopist training level between CAC and SC. We also evaluated the number of polyps and adenomas according to their size between CAC and SC.RESULTS: Overall, PDR and ADR using CAC were significantly higher than those using SC for both whole colon(48.5% vs 40.7%, P = 0.012; 35.7% vs 28.3%, P = 0.012) and right-side colon(35.3% vs 26.6%, P = 0.002; 27.0% vs 16.9%, P < 0.001). The number of polyps and adenomas per patient using CAC was significantly higher than that using SC for both the whole colon(1.07 ± 1.59 vs 0.82 ± 1.31, P = 0.008; 0.72 ± 1.32 vs 0.50 ± 1.01, P = 0.003) and right-side colon(0.66 ± 1.18 vs 0.41 ± 0.83, P < 0.001; 0.46 ± 0.97 vs 0.25 ± 0.67, P < 0.001). In the trainee group, the PDR and ADR using CAC were significantly higher than those using SC for both the whole colon(46.7% vs 39.7%, P = 0.040; 33.9% vs 26.0%, P =0.012) and right-side colon(34.2% vs 26.5%, P = 0.015; 25.3% vs 15.9%, P = 0.001). In the expert group, the PDR and ADR using CAC were significantly higher than those using SC only for the right-side colon(42.1% vs 27.0%, P =0.035; 36.8% vs 21.0%, P = 0.020).CONCLUSION: CAC is more effective than SC for detection of colorectal polyps and adenomas, especially when performed by trainees and when the lesions are located in the right-side colon.