Genome-wide association study of Crohn's disease in Koreans revealed three new susceptibility loci and common attributes of genetic susceptibility across ethnic populations.

OBJECTIVE: Crohn's disease (CD) is an intractable inflammatory bowel disease (IBD) of unknown cause. Recent meta-analysis of the genome-wide association studies (GWAS) and Immunochip data identified 163 susceptibility loci to IBD in Caucasians, however there are limited studies in other populations. METHODS: We performed a GWAS and two validation studies in the Korean population comprising a total of 2311 patients with CD and 2442 controls. RESULTS: We confirmed four previously reported loci: TNFSF15, IL23R, the major histocompatibility complex region, and the RNASET2-FGFR1OP-CCR6 region. We identified three new susceptibility loci at genome-wide significance: rs6856616 at 4p14 (OR=1.43, combined p=3.60×10(-14)), rs11195128 at 10q25 (OR=1.42, combined p=1.55×10(-10)) and rs11235667 at 11q13 (OR=1.46, combined p=7.15×10(-9)), implicating ATG16L2 and/or FCHSD2 as novel susceptibility genes for CD. Further analysis of the 11q13 locus revealed a non-synonymous single nucleotide polymorphism (SNP) (R220W/rs11235604) in the evolutionarily conserved region of ATG16L2 with stronger association (OR=1.61, combined p=2.44×10(-12)) than rs11235667, suggesting ATG16L2 as a novel susceptibility gene for CD and rs11235604 to be a potential causal variant of the association. Two of the three SNPs (rs6856616 (p=0.00024) and rs11195128 (p=5.32×10(-5))) showed consistent patterns of association in the International IBD Genetics Consortium dataset. Together, the novel and replicated loci accounted for 5.31% of the total genetic variance for CD risk in Koreans. CONCLUSIONS: Our study provides new biological insight to CD and supports the complementary value of genetic studies in different populations.

Risk of adenomas with high-risk characteristics based on two previous colonoscopy.

BACKGROUND AND AIM: The recommended intervals between surveillance colonoscopies are based on the most recent examination findings. However, whether the two previous colonoscopies affect second surveillance colonoscopic findings is not established. The aim of this study is to estimate the risk of obtaining high-risk findings (HRF) on the next surveillance colonoscopy using the results of two previous colonoscopies, and to estimate the appropriate time interval for the next surveillance colonoscopy. METHODS: Among subjects who underwent screening colonoscopy during January 2002-December 2009, patients who underwent second surveillance colonoscopy before June 2012 were enrolled. "No adenoma" was defined as a hyperplastic polyp or no polyp, "low-risk findings (LRF)" as one or two small (< 1 cm) tubular adenomas, and "HRF" as advanced adenoma, cancer, or any sized multiple (≥ 3) adenomas. RESULTS: Among enrolled 852 subjects, 65 (7.6%) had HRF at second surveillance colonoscopy. Multivariate analysis showed that HRF on second surveillance colonoscopy were associated with male and HRF on screening colonoscopy (all, P < 0.01). In subjects with LRF on first surveillance colonoscopy, HRF on the screening colonoscopy significantly affected the detection of HRF on second surveillance colonoscopy (P < 0.01). Patients with HRF on screening colonoscopy and LRF on the first surveillance colonoscopy had no different risk of HRF on second surveillance colonoscopy from those with HRF on first surveillance colonoscopy (P > 0.05). CONCLUSIONS: The HRF on second surveillance are significantly associated with previous two colonoscopic results. In patients with LRF on first surveillance, screening colonoscopic findings should be considered to determine the optimal surveillance interval.

Comparative study of Helicobacter pylori eradication rates with 5-day quadruple "concomitant" therapy and 7-day standard triple therapy.

BACKGROUND: Several studies have shown the superiority of concomitant quadruple therapy containing 3 antibiotics over triple therapy for Helicobacter pylori infection. The aim of this study was to compare concomitant quadruple therapy with standard triple therapy for first-line H. pylori eradication. METHODS: A total of 270 patients with proven H. pylori infection were randomly assigned to one of 2 regimens: amoxicillin 1000 mg with clarithromycin 500 mg and lansoprazole 30 mg twice daily for 7 days (triple therapy) or amoxicillin 1000 mg with clarithromycin 500 mg, metronidazole 500 mg, and lansoprazole 30 mg twice daily for 5 days (concomitant therapy). The success of eradication was evaluated 4 to 5 weeks after completion of treatment. RESULTS: Eradication rates were 86.1% in the triple therapy and 91.4% in the concomitant therapy (per protocol), but the difference was not statistically significant. Mild adverse events were more frequently reported in the concomitant-therapy group (35.6%) than in the triple-therapy group (25.2%) (P=0.09). CONCLUSIONS: Five-day quadruple concomitant therapy eradicated H. pylori in over 90% of patients. Accordingly, concomitant therapy is thought to be a promising alternative to triple therapy as a first-line treatment regimen for H. pylori eradication.

Is colonoscopic screening necessary for patients with gastric adenoma or cancer?

BACKGROUND: Since colorectal adenoma or cancer is commonly associated with gastric adenoma or cancer, early colorectal adenoma detection can affect the survival of gastric adenoma or cancer patients. AIMS: The purpose here was to investigate the colorectal adenoma or cancer prevalence and evaluate the necessity for screening colonoscopy in gastric adenoma or cancer patients. PATIENTS AND METHODS: From September 2005 through August 2010, 857 patients younger than 70 years who had gastric adenoma or cancer were enrolled. Healthy age- and sex-matched controls were selected from the general screening population. The prevalence and risk of colorectal adenoma or cancer were compared between the participants and the controls. RESULTS: Data from 416 patients in the gastric neoplasm group (123 with gastric adenoma and 293 with gastric cancer) and 416 healthy control group participants were included in the statistical analysis. The presence of gastric adenoma or cancer was an independent risk factor for colorectal neoplasm (OR = 1.348, 95 % CI = 1.001-1.815). Patients with diffuse type gastric cancer had a lower prevalence of colorectal adenoma or cancer than those with gastric adenoma or intestinal type cancer. In gastric cancer patients younger than 50 years, intestinal type histology was significantly associated with colorectal adenoma or cancer (OR = 3.838, 95 % CI = 1.077-13.677). CONCLUSIONS: The colorectal adenoma or cancer risk was significantly increased in patients with gastric adenoma or cancer. Therefore, screening colonoscopy should be considered for gastric adenoma or cancer patients including young patients, in the case of intestinal type gastric cancer.

Small bowel pseudomelanosis associated with oral iron therapy.

An accumulation of pigment deposits on mucosa, called melanosis or pseudomelanosis, of the small bowel is observed infrequently during endoscopic examination. We describe 6 cases of small bowel pseudomelanosis; the possible etiology of which was chronic iron intake. We observed numerous brown spots in duodenum, jejunum, and terminal ileum during upper and lower endoscopy. Interestingly, all patients have been taking oral iron for several years. Histology showed pigment depositions within macrophages of the lamina propria and a positive Prussian blue stain indicating hemosiderin deposition. Herein, we demonstrate that long term iron therapy may result in pseudomelanosis of small bowel, such as duodenum, jejunum, and ileum.

Effectiveness of three times daily lansoprazole/amoxicillin dual therapy for Helicobacter pylori infection in Korea.

AIM: We compared three times daily dual therapy with standard triple therapy for effectiveness and safety in H. pylori infection. METHODS: Two hundred and four H. pylori positive patients with peptic ulcer were randomly assigned to one of two regimens: (i) triple therapy with amoxicillin, clarithromycin and lansoprazole twice daily for 2 weeks or (ii) dual therapy with amoxicillin and lansoprazole three times daily for 2 weeks. The success of eradication was evaluated 4 to 5 weeks after completing treatment. RESULTS: The eradication rate was 82.8% in the triple therapy group and 78.4% in the dual therapy group by per protocol analysis. This difference was not significant (P= 0.573). Adverse events were more frequent in the triple therapy group than in the dual therapy group (P= 0.002). CONCLUSIONS: Because dual therapy had fewer side effects than triple therapy and a similar eradication rate, dual therapy may provide an acceptable alternative first line therapy for H. pylori eradication in Korea.

Validation of a Mayo post-operative mortality risk prediction model in Korean cirrhotic patients.

BACKGROUND: Patients with cirrhosis have an increased risk of mortality after surgery. In 2007, a new model was suggested to calculate mortality risk at specific time points after surgery at the Mayo clinic. AIMS: We investigated the mortality risks in Korean cirrhotic patients who underwent various surgeries and applied the Mayo clinic model to our study populations. METHODS: We conducted a retrospective review of the charts of 160 patients with cirrhosis who underwent surgical procedures under general anaesthesia between January 1996 and December 2006 at two hospitals. RESULTS: The overall 30-, 90-day and 1-year mortality rates were 7.5, 9.4 and 10.6% respectively. In multivariate analysis, the Child-Turcotte-Pugh (CTP) score, model for end-stage liver disease (MELD) and the American Society of Anesthesiologists (ASA) physical status classification and age were significantly associated with mortality. The area under the receiver operating characteristic (AUROC) from the calculated value using Mayo model as a predictor of 30-, 90-day and 1-year mortality was 0.832, 0.803 and 0.822 respectively, of which, 1-year mortality was significantly different from AUROC of mortality prediction based on our patient's data (P=0.025). In addition, the mean of predicted 1-year mortality rate (22.6±12.0%) using Mayo model was significantly higher than that from observed (8.9±1.4%, P<0.01). CONCLUSIONS: The CTP score or MELD score or ASA physical class and age were found to be significant predictors of post-operative mortality in cirrhotic patients. The risk prediction model developed at the Mayo clinic showed good performance in Korean cirrhotic patients. However, we found that the model tended to overestimate mortality, especially 1 year after surgery.

Effectiveness and safety of repeated quadruple therapy in Helicobacter pylori infection after failure of second-line quadruple therapy: repeated quadruple therapy as a third-line therapy.

BACKGROUNDS: Quadruple therapy using a proton-pump inhibitor, bismuth, metronidazole, and tetracycline is a standard second-line therapy for Helicobacter pylori infection, achieving an eradication rate of about 80% in Korea. A standard third-line therapy is not currently established, although various protocols have been proposed. We performed this study to evaluate the effectiveness of a retrial with quadruple therapy before starting a third-line treatment with new drugs. MATERIALS AND METHODS: In 80 of 746 patients treated with a second-line quadruple therapy at the Korea University Ansan Hospital between January 2002 and September 2010, treatment for H. pylori had failed, and 45 of these patients were eligible for this study. Eradication of H. pylori was assessed by repeated endoscopy or by the (13) C-urea breath test at least 4 weeks after therapy. The patients with treatment failure were treated again with quadruple regimen for 2 weeks and reevaluated for treatment effectiveness and safety. RESULTS: The eradication rate with second-line quadruple therapy was 86.9%. Of the 80 patients who failed treatment for H. pylori with the initial second-line quadruple therapy, 64 patients were treated again with the same regimen. Of the 45 retreated patients in this study, three patients were lost to follow-up and two complied poorly with medication. The eradication rate in the 40 patients retreated was 75.0% at per-protocol analysis. Seventeen patients experienced mild adverse events. CONCLUSIONS: A retrial of quadruple therapy before use of a third-line therapy may be safe and effective for patients who fail to respond to second-line quadruple therapy.

Endovascular management for isolated spontaneous dissection of the superior mesenteric artery: report of two cases and literature review.

The clinical course and treatment strategies of isolated superior mesenteric artery (SMA) dissection have not been fully investigated. Two cases of uncontrolled abdominal pain caused by isolated SMA dissection were successfully treated with percutaneous endovascular stent placement. At follow-up 6 months later, computed tomography confirmed that the lesions had stabilized. The patients remained symptom free at 14- and 13-month follow-up, respectively. The present report describes these two cases of isolated SMA dissection treated successfully with percutaneous endovascular stent placement, along with a review of the related literature.

Clinical characteristics of small bowel tumors diagnosed by double-balloon endoscopy: KASID multi-center study.

BACKGROUND: Small bowel tumors are relatively rare, and their confirmative diagnosis before surgery is not easy. AIMS: This study was performed to investigate the clinical characteristics of patients with small bowel tumors who received double-balloon enteroscopy (DBE). Secondary end points were to evaluate the usefulness and safety of DBE for the diagnosis of patients with suspected SB tumors derived from other previous procedures. METHODS: We retrospectively analyzed consecutive DBE examinations to explore the small intestine in eight university hospitals over a 5-year period. RESULTS: A total of 877 DBE examinations (per oral 487, per anal 390) were performed in 645 patients (405 males, mean age 48.2 years). Small bowel tumors were diagnosed in 112 patients (17.4%), of which 38 patients had benign polyps, 29 had gastrointestinal stromal tumors/leiomyomata, 18 had lymphomas, 14 had adenocarcinomas, five had metastatic or invasive cancers, five had lipomas, and three patients had cystic tumors. The main reasons for DBE among patients with small bowel tumors were obscure gastrointestinal bleeding (OGIB, 40.2%) followed by abnormal imaging study (25.2%). The concordance rate of diagnoses based on DBE with diagnoses based on small bowel follow-through, CT, and capsule endoscopy among patients with small bowel tumors was 68.9% (42/61), 75.3% (70/93), and 78.3% (18/23), respectively. Therapeutic plans were changed due to the DBE results in 64.2% of patients with small bowel tumors. CONCLUSIONS: Approximately one-sixth of patients who received DBE had small bowel tumors, and the most common reason for DBE among patients with small bowel tumors was OGIB. DBE is a useful method for the confirmative diagnosis of small bowel tumors and has a good clinical impact on therapeutic plans and short-term clinical results.

Clinical courses after administration of oral corticosteroids in patients with severely cholestatic acute hepatitis A; three cases.

Acute hepatitis A is currently outbreaking in Korea. Although prognosis of acute hepatitis A is generally favorable, a minority of patients are accompanied by fatal complications. Severe cholestasis is one of the important causes of prolonged hospitalization in patients with acute hepatitis A. In such cases, higher chances of additional complications and increased medical costs are inevitable. We report three cases of severely cholestatic hepatitis A, who showed favorable responses to oral corticosteroids. Thirty milligram of prednisolone was initiated and tapered according to the responses. Rapid improvement was observed in all cases without side effects. We suggest that corticosteroid administration can be useful in hepatitis A patients with severe cholestasis who do not show improvement by conservative managements. Clinical trial will be needed to evaluate effectiveness of corticosteroids in these patients.

[Clinical characteristics of chronic pancreatitis according to the history of pancreatitis].

BACKGROUND/AIMS: Chronic pancreatitis (CP) is characterized clinically by a broad spectrum of variable features depending on many factors such as etiology, stage of the disease, and the presence of local complications. The aims of this study were to investigate the clinical aspect of CP and to analyze the characteristics according to the history of pancreatitis. METHODS: Eighty nine medical records from the patients who were diagnosed as CP at Korea University Ansan Hospital from January 1997 through December 2007 were reviewed retrospectively. After patients were divided into two groups according to the previous history of pancreatitis: the group I (n=34, no history of pancreatitis) and II (n=43, history of pancreatitis more than once), the clinical characteristics of two groups were compared. RESULTS: The mean age was 50+/-13.2 years and the male to female ratio was 5:1. Alcohol was the cause of CP in 71.9%, and 23.6% had no evident cause. Age (53.4+/-15.5 vs. 46.2+/-11.5, p=0.021), etiology (idiopathic 41.2% vs. 11.6%, p=0.004), and the presence of abdominal pain (73.5% vs. 100%, p=0.030) were significantly different between group I and II. However, in comparison of other factors that reflected the advanced stage of CP such as presence of pancreatic calcification, complications, and Cambridge grade on ERCP, there was no significant difference. CONCLUSIONS: Since CP which present, as the first manifestation shows much an advanced stage, the method for early diagnosis of CP is particularly needed.

[A case of advanced hepatocellular carcinoma with portal vein tumor invasion controlled by percutaneous ethanol injection therapy].

Portal vein invasion is a grave prognostic indicator in the setting of hepatocellular carcinoma (HCC). There is currently no effective method for preventing the invasion of HCC into the main portal vein. We report here a case of advanced HCC with portal vein tumor thrombosis that was effectively treated with percutaneous ethanol injection (PEI), having previously enabled subsequent successive transarterial chemoembolization (TACE). A 60-year-old male patient was diagnosed with a huge HCC, based on computed tomography and angiographic findings. Despite two sessions of TACE, the tumor invaded the right portal vein. PEI was performed on the malignant portal vein thrombosis, and three sessions thereof reduced the extent of tumor thrombi in the portal vein. Successive TACEs were performed to treat the HCC in the hepatic parenchyma. The patient was still living 19 months after the first PEI with no evidence of tumor recurrence, and his liver function remained well preserved.

[Two cases of toxic hepatitis caused by arrowroot juice].

Herbal remedies and health foods are widely used, and their side effects have been reported. We describe two cases of symptomatic toxic hepatitis that developed in middle-aged women after ingesting arrowroot juice. The clinical manifestations were nausea, vomiting, and jaundice. The diagnosis of toxic hepatitis was made using the Roussel Uclaf Causality Assessment Method score on the basis of the patient's history and laboratory data. After supportive care, the patients showed rapid improvements of clinical symptoms, laboratory findings, and liver stiffness. Clinicians should be aware that the consumption of arrowroot juice can cause toxic hepatitis.

Comparative study of Helicobacter pylori eradication rates of twice-versus four-times-daily amoxicillin administered with proton pump inhibitor and clarithromycin: a randomized study.

BACKGROUND: Proton pump inhibitor (PPI)-containing triple therapy with clarithromycin and amoxicillin is now a standard regimen for Helicobacter pylori eradication in Korea. Amoxicillin has time-dependent bactericidal activity against H. pylori; we therefore assumed a dosing schedule of amoxicillin would affect the eradication rate of H. pylori. The purpose of this study was to evaluate and compare the efficacy of different amoxicillin dosing schedules for the eradication of H. pylori. MATERIALS AND METHODS: One hundred and eighty-six patients with H. pylori infection were eligible for this study. Patients were randomly assigned to one of two regimens: amoxicillin 1000 mg with clarithromycin 500 mg and omeprazole 20 mg twice daily for 2 weeks (BID group, n = 93), or amoxicillin 500 mg four times daily with clarithromycin 500 mg and omeprazole 20 mg twice daily for 2 weeks (QID group, n = 93). The success of H. pylori eradication was evaluated 4-5 weeks after completing treatment. RESULTS: Overall eradication rate was 90.3%, and eradication rates were 91.4% in the BID group and 89.2% in the QID group (p = 0.62). Compliances was 95.7% in the BID group and 93.5% in the QID group (p = 0.516); this was the only factor that significantly affected H. pylori eradication in this study. Side effects in both groups were generally mild. CONCLUSIONS: Amoxicillin regimens with PPI and clarithromycin are found to be equally effective and safe in both the BID and QID groups for H. pylori eradication. Therefore, considering patient's comfort, we recommend a twice daily amoxicillin regimen.

[A case of systemic amyloidosis with pancreatic involvement mimicking autoimmune pancreatitis].

Systemic amyloidosis is a disorder characterized by extracellular deposition of amyloid in various organs and tissues including the kidney, heart, and liver. However, pancreatic involvement is rare, and has not been reported in Korea. Systemic amyloisosis involving pancreas needs to be differentiated from several pancreatic diseases because of diffuse pancreatic enlargement and partial stricture or obstruction of main pancreatic duct. Recently, we experienced a 60-year old man who was suspected as autoimmune pancreatitis or infiltrative disorders on imaging studies, and finally diagnosed as systemic amyloidosis involving pancreas and liver on biopsy examination. We report the case with review of the relevant literatures.

[Accessibility of peritoneal organs according to the routes of approach in NOTES].

BACKGROUND/AIMS: Natural orifice transluminal endoscopic surgery (NOTES) is a new era of minimally invasive surgery which has the potential to offer scarless surgery. So far, numerous reports on various routes to peritoneal organs in NOTES have been published. In case of transgastric approach, it is more inconvenient than transcolonic approach to access upper abdominal organs because of retroflexion. However, most data were subjective and there was no report examining the best access route for the exploration of peritoneal organs. The aim of this study was to evaluate the best access route according to the abdominal organs objectively. METHODS: Six female pigs weighing 30 to 35 kg were placed under general anesthesia. Incisions were made on both anterior wall of stomach body and rectosigmoid colon 15 to 20 cm above anal verge, respectively. Then, via each incision site, we evaluated the endoscopic visibility and checked the elapsed time to access abdominal organs in sequence [(gallbladder (GB), spleen, bladder, uterus, and ovary)]. RESULTS: On comparison of the mean time to approach each organs, GB and ovary showed statistical difference in the mean time to approach between transgastric and transcolonic approaches. It took relatively shorter time to access GB via transcolonic route than transgastric route (352.3+/-80.1 sec vs. 222.2+/-82.0 sec, p=0.021). Next, we evaluated the time to access upper organs (GB and spleen) and lower organs (bladder, uterus and ovary). In case of lower organs, it showed no difference in time between transgastric and transcolonic approaches. However, to explore upper organs, transcolonic route was more favorable than transgastric route (351.8+/-80.7 sec vs. 273.3+/-110.3 sec, p=0.002). CONCLUSIONS: For exploration of lower organs, there is statistically no significant difference in time between transgastric and transcolonic approaches. But, in case of upper organs, transcolonic approach is superior to transgastric approach.

[Analysis of the factors that affect the mortality rate in severe acute pancreatitis].

BACKGROUND/AIMS: Severe acute pancreatitis occurs in about 20% of the patients with acute pancreatitis and can be associated with multiorgan failure and local complications. In patients with predicted severe acute pancreatitis, overall mortality rates are about 15-30%. The aim of this study was to determine the factors correlated with mortality in patients with severe acute pancreatitis. METHODS: We reviewed five hundread and seventy two consecutive cases of acute pancreatitis from January, 2000 to December, 2005. Of them, 109 patients who fulfilled the criteria of Atlanta classification for severe acute pancreatitis were enrolled. Data were collected by chart reviews including age, gender, etiology, body mass index (BMI), modified Glasgow score, APACHE II score, APACHE III score, Balthazar CT index, and other laboratory parameters performed within 48 hours after the initial admission. RESULTS: Severe acute pancreatitis was most commonly caused by alcohol. Overall mortality rate was 20.2% in severe acute pancreatitis and 10 (45%) deaths occurred within the first week. Multiple logistic regression analysis identified serum creatinine, corrected calcium concentrations, and CT index as predictors of mortality in patients with severe acute pancreatitis. The risk score (R) was calculated by combining 3 prognostic values with regression coefficients; R=2.512 loge (creatinine mg/dL)+1.729 loge (CT index)??4.780 loge (corrected calcium mg/dL). The AUC for this score was 0.877 and a cutoff level of 0 was determined to predict the mortality with 83.3% sensitivity and 89.5% specificity. CONCLUSIONS: The newly designed risk score comprising 3 parameters can be used as the significant early predictor for hospital mortality in severe acute pancreatitis.

Comparison of postpolypectomy bleeding between epinephrine and saline submucosal injection for large colon polyps by conventional polypectomy: a prospective randomized, multicenter study.

AIM: To evaluate and compare the clinical outcomes of prophylactic submucosal saline-epinephrine injection and saline injection alone for large colon polyps by conventional polypectomy. METHODS: A prospective study was conducted from July 2003 to July 2004 at 11 tertiary endoscopic centers. Large colon polyps (> 10 mm in diameter) were randomized to undergo endoscopic polypectomy with submucosal saline-epinephrine injection (epinephrine group) or normal saline injection (saline group). Endoscopic polypectomy was performed by the conventional snare method, and early (< 12 h) and late bleeding complications (12 h-30 d) were observed. RESULTS: A total of 561 polyps in 486 patients were resected by endoscopic polypectomy. Overall, bleeding complications occurred in 7.6% (37/486) of the patients, including 4.9% (12/244) in the epinephrine group, and 10.3% (25/242) in the saline group. Early and late postpolypectomy bleeding (PPB) occurred in 6.6% (32/486) and 1% (5/486) of the patients, respectively, including 4.5% (11/244), 0.4% (1/244) in the epinephrine group, and 8.7% (21/242), 1.7% (4/242) in the saline group. No significant differences in the rates of overall, early and late PPB were observed between the 2 groups. Multivariate stepwise logistic regression analysis revealed that large size (> 2 cm) and neoplastic polyps were independently and significantly associated with the presence of PPB. CONCLUSION: The prophylactic submucosal injection of diluted epinephrine does not appear to provide an additional advantage over the saline injection alone for the prevention of PPB.

Clinical significance of small colorectal adenoma less than 10 mm: the KASID study.

BACKGROUND/AIMS: Polypectomy is the current modality of choice to prevent benign colorectal adenoma from progressing to an invasive cancer. However, in cases of small colorectal adenoma, it remains unclear as to whether polypectomy is actually an effective treatment modality. We evaluated the clinical significance of polypectomy in cases of small colorectal adenomas, measuring less than 10 mm. METHODOLOGY: All colonoscopies were performed at 11 Korean tertiary medical centers, between July 2003 and March 2004. A total of 5996 colorectal adenomas were detected and divided into 5 groups according to their size (Group 1; 1-5 mm, Group 2; 6-7 mm, Group 3; 8-9 mm, Group 4; 10-19 mm, Group 5; more than 20 mm). The term 'advanced adenoma' refers here to tubular adenomas with diameters of at least 10 mm, or to tubulovillous, villous, or high-grade dysplasia, irrespective of size. 'Cancer' here is defined as the invasion of malignant cells beyond the muscularis mucosa. RESULTS: As the sizes of the adenomas increased, the prevalence of advanced adenoma was also observed to increase. In Groups 2 and 3, the prevalence of tubulovillous or villous adenoma were higher than was expected (5.2% and 6.6%, p < 0.001). Interestingly enough, in Group 2, the prevalence of cancer was at least as high as in Group 4 (0.7% vs. 0.5%, p < 0.001). CONCLUSIONS: In cases of small colorectal adenomas, measuring between 6 and 9 mm, the prevalence of cancer was at least as high as that seen in the cases of colorectal adenomas measuring between 10 and 19 mm. Therefore, small colorectal adenomas measuring between 6 and 9 mm should not be ignored, in order to decrease the prevalence of colorectal cancer.