Development of a greenhouse gas - air pollution interactions and synergies model for Korea (GAINS-Korea).

This study aimed to create Greenhouse Gas - Air Pollution Interactions and Synergies (GAINS)-Korea, an integrated model for evaluating climate and air quality policies in Korea, modeled after the international GAINS model. GAINS-Korea incorporates specific Korean data and enhances granularity for enabling local government-level analysis. The model includes source-receptor matrices used to simulate pollutant dispersion in Korea, generated through CAMx air quality modeling. GAINS-Korea's performance was evaluated by examining different scenarios for South Korea. The business as usual scenario projected emissions from 2010 to 2030, while the air quality scenario included policies to reduce air pollutants in line with air quality and greenhouse gas control plans. The maximum feasible reduction scenario incorporated more aggressive reduction technologies along with air quality measures. The developed model enabled the assessment of emission reduction effects by both greenhouse gas and air pollutant emission reduction policies across 17 local governments in Korea, including changes in PM2.5 (particulate matter less than 2.5 µm) concentration and associated benefits, such as reduced premature deaths. The model also provides a range of visualization tools for comparative analysis among different scenarios, making it a valuable resource for policy planning and evaluation, and supporting decision-making processes.

PM2.5 Forecast in Korea using the Long Short-Term Memory (LSTM) Model.

The National Institute of Environmental Research, under the Ministry of Environment of Korea, provides two-day forecasts, through AirKorea, of the concentration of particulate matter with diameters of ≤ 2.5 µm (PM2.5) in terms of four grades (low, moderate, high, and very high) over 19 districts nationwide. Particulate grades are subjectively designated by human forecasters based on forecast results from the Community Multiscale Air Quality (CMAQ) and artificial intelligence (AI) models in conjunction with weather patterns. This study evaluates forecasts from the long short-term memory (LSTM) algorithm relative to those from CMAQ-solely and AirKorea using observations from 2019. The skills of the one-day PM2.5 forecasts over the 19 districts were 39-70% for CMAQ, 72-79% for LSTM, and 73-80% for AirKorea; the AI forecasts showed comparable skills to the human forecasters at AirKorea. The one-day forecast skill levels of high and very high PM2.5 pollution grades are 31-98%, 31-74%, and 39-81% for the CMAQ-solely, the LSTM, and the AirKorea forecasts, respectively. Despite good skills for forecasting the high and very high events, CMAQ-solely forecasts also generate substantially higher false alarm rates (up to 86%) than the LSTM and AirKorea forecasts (up to 58%). Hence, applying only the LSTM model to the CMAQ forecasts can yield reasonable forecast skill levels comparable to the operational AirKorea forecasts that elaborately combine the CMAQ model, AI models, and human forecasters. The present results suggest that applications of appropriate AI models can greatly enhance PM2.5 forecast skills for Korea in a more objective way. Supplementary Information: The online version contains supplementary material available at 10.1007/s13143-022-00293-2.

A novel statistical-dynamical method for a seasonal forecast of particular matter in South Korea.

Societal concerns about air quality in East Asia are still growing despite country-level efforts to reduce air pollution emissions. In coping with this growing concern, the government and the public demand a longer­lead forecast of air quality to ensure sufficient response time until society prepares for countermeasures such as a temporary reduction of specific emission sources. Here we propose a novel method that produces skillful seasonal forecasting of wintertime (December to February) PM10 concentration over South Korea. The method is based on the idea that climate condition and air quality have co-variability in the seasonal time scales and that the state-of-art seasonal prediction model will benefit air quality forecasting. More specifically, a linear regression model is constructed to link observed winter PM10 concentration and climate variables where the predicted climate variables were furnished from NCEP CFSv2 forecast initialized during autumn. In this case, climate variables were selected as predictors of the model because they are not only physically related to air quality but also 'predictable' in CFS hindcast. Through analysis of retrospective forecasts of 20 winters for the period 2001-2020, we found this model shows statistically significant skill for the seasonal forecast of wintertime PM10 concentration.

Statistical Seasonal Forecasting of Winter and Spring PM2.5 Concentrations Over the Korean Peninsula.

Concentrations of fine particulate matter smaller than 2.5 µm in diameter (PM2.5) over the Korean Peninsula experience year-to-year variations due to interannual variation in climate conditions. This study develops a multiple linear regression model based on slowly varying boundary conditions to predict winter and spring PM2.5 concentrations at 1-3-month lead times. Nation-wide observations of Korea, which began in 2015, is extended back to 2005 using the local Seoul government's observations, constructing a long-term dataset covering the 2005-2019 period. Using the forward selection stepwise regression approach, we identify sea surface temperature (SST), soil moisture, and 2-m air temperature as predictors for the model, while rejecting sea ice concentration and snow depth due to weak correlations with seasonal PM2.5 concentrations. For the wintertime (December-January-February, DJF), the model based on SSTs over the equatorial Atlantic and soil moisture over the eastern Europe along with the linear PM2.5 concentration trend generates a 3-month forecasts that shows a 0.69 correlation with observations. For the springtime (March-April-May, MAM), the accuracy of the model using SSTs over North Pacific and 2-m air temperature over East Asia increases to 0.75. Additionally, we find a linear relationship between the seasonal mean PM2.5 concentration and an extreme metric, i.e., seasonal number of high PM2.5 concentration days. Supplementary Information: The online version contains supplementary material available at 10.1007/s13143-022-00275-4.

A novel CMAQ-CNN hybrid model to forecast hourly surface-ozone concentrations 14 days in advance.

Issues regarding air quality and related health concerns have prompted this study, which develops an accurate and computationally fast, efficient hybrid modeling system that combines numerical modeling and machine learning for forecasting concentrations of surface ozone. Currently available numerical modeling systems for air quality predictions (e.g., CMAQ) can forecast 24 to 48 h in advance. In this study, we develop a modeling system based on a convolutional neural network (CNN) model that is not only fast but covers a temporal period of two weeks with a resolution as small as a single hour for 255 stations. The CNN model uses meteorology from the Weather Research and Forecasting model (processed by the Meteorology-Chemistry Interface Processor), forecasted air quality from the Community Multi-scale Air Quality Model (CMAQ), and previous 24-h concentrations of various measurable air quality parameters as inputs and predicts the following 14-day hourly surface ozone concentrations. The model achieves an average accuracy of 0.91 in terms of the index of agreement for the first day and 0.78 for the fourteenth day, while the average index of agreement for one day ahead prediction from the CMAQ is 0.77. Through this study, we intend to amalgamate the best features of numerical modeling (i.e., fine spatial resolution) and a deep neural network (i.e., computation speed and accuracy) to achieve more accurate spatio-temporal predictions of hourly ozone concentrations. Although the primary purpose of this study is the prediction of hourly ozone concentrations, the system can be extended to various other pollutants.

Oscillopsia associated with pseudoaccommodation in pseudophakia.

Oscillopsia associated with near fixation after multifocal intraocular lens (IOL) implantation has not been fully recognized. A 46-year-old woman presented with shaking of vision in both eyes during near fixation after uneventful implantation of a single-piece multifocal posterior chamber IOL in both eyes. There was no sign of zonular weakness in either eye before or during cataract surgery, and the postoperative course was uneventful. Visual acuity was 20/25 in both eyes without correction. There was no IOL oscillation with distant fixation; however, when she changed her focus from a distant to a near object, the IOLs started to oscillate in both eyes, which was assumed to be the cause of her oscillopsia. On cycloplegia, there was no IOL oscillation either with distant or near fixation. A rare cause of oscillopsia associated with pseudoaccommodation after IOL implantation should be recognized.

Comparative assessment of net CO2 exchange across an urbanization gradient in Korea based on eddy covariance measurements.

BACKGROUND: It is important to quantify changes in CO2 sources and sinks with land use and land cover change. In the last several decades, carbon sources and sinks in East Asia have been altered by intensive land cover changes due to rapid economic growth and related urbanization. To understand impact of urbanization on carbon cycle in the monsoon Asia, we analyze net CO2 exchanges for various land cover types across an urbanization gradient in Korea covering high-rise high-density residential, suburban, cropland, and subtropical forest areas. RESULTS: Our analysis demonstrates that the urban residential and suburban areas are constant CO2 sources throughout the year (2.75 and 1.02 kg C m-2 year-1 at the urban and suburban sites), and the net CO2 emission indicate impacts of urban vegetation that responds to the seasonal progression of the monsoon. However, the total random uncertainties of measurement are much larger in the urban and suburban areas than at the nonurban sites, which can make it challenging to obtain accurate urban flux measurements. The cropland and forest sites are strong carbon sinks because of a double-cropping system and favorable climate conditions during the study period, respectively (- 0.73 and - 0.60 kg C m-2 year-1 at the cropland and forest sites, respectively). The urban area of high population density (15,000 persons km-2) shows a relatively weak CO2 emission rate per capita (0.7 t CO2 year-1 person-1), especially in winter because of a district heating system and smaller traffic volume. The suburban area shows larger net CO2 emissions per capita (4.9 t CO2 year-1 person-1) because of a high traffic volume, despite a smaller building fraction and population density (770 persons km-2). CONCLUSIONS: We show that in situ flux observation is challenging because of its larger random uncertainty and this larger uncertainty should be carefully considered in urban studies. Our findings indicate the important role of urban vegetation in the carbon balance and its interaction with the monsoon activity in East Asia. Urban planning in the monsoon Asia must consider interaction on change in the monsoon activity and urban structure and function for sustainable city in a changing climate.

Clinical Characteristics and Incidence of Perianal Diseases in Patients With Ulcerative Colitis.

PURPOSE: While perianal disease (PAD) is a characteristic of patients with Crohn disease, it has been overlooked in patients with ulcerative colitis (UC). Thus, our study aimed to analyze the incidence and the clinical features of PAD in patients with UC. METHODS: We reviewed the data on 944 patients with an initial diagnosis of UC from October 2003 to October 2015. PAD was categorized as hemorrhoids, anal fissures, abscesses, and fistulae after anoscopic examination by experienced proctologists. Data on patients' demographics, incidence and types of PAD, medications, surgical therapies, and clinical course were analyzed. RESULTS: The median follow-up period was 58 months (range, 12-142 months). Of the 944 UC patients, the cumulative incidence rates of PAD were 8.1% and 16.0% at 5 and 10 years, respectively. The incidence rates of bleeding hemorrhoids, anal fissures, abscesses, and fistulae at 10 years were 6.7%, 5.3%, 2.6%, and 3.4%, respectively. The cumulative incidence rates of perianal sepsis (abscess or fistula) were 2.2% and 4.5% at 5 and 10 years, respectively. In the multivariate analyses, male sex (risk ratio [RR], 4.6; 95% confidence interval [CI], 1.7-12.5) and extensive disease (RR, 4.2; 95% CI, 1.6-10.9) were significantly associated with the development of perianal sepsis. CONCLUSION: Although the clinical course of PAD in patients with UC is not serious, in clinical practice, PAD is not rare in such patients. Therefore, careful examination and appropriate management for PAD is needed if the quality of life for patients with UC is to be improved.

Comparison of partially-absorbable lightweight mesh with heavyweight mesh for inguinal hernia repair: multicenter randomized study.

PURPOSE: Prosthetic mesh is widely used for inguinal hernia repair; however, pain and stiffness can develop. This study was a prospective, multicenter, single-blind, randomized trial to assess postoperative pain and quality of life according to mesh type after inguinal hernia repair. METHODS: Forty-seven patients who underwent Lichtenstein repair for unilateral inguinal hernia with prosthetic mesh were enrolled and randomly allocated to the partially-absorbable lightweight mesh (LW group, n = 24) or heavyweight mesh group (HW group, n = 23). Data were collected using a visual analogue scale (VAS), Carolinas Comfort Scale (CCS), and Activities Assessment Scale (AAS) at screening and postoperative day 1, 7, 90, and 120; foreign body sensation, sense of stiffness, and sense of pull during activity were also evaluated. RESULTS: There were no significant differences in patients' demographics and clinical characteristics between groups. The VAS at day 90 was significantly lower in the LW group (0.46 ± 0.78 vs. 0.96 ± 0.82, P = 0.027). The CCS and AAS were significantly lower in the LW group at day 1 (51.33 ± 20.29 vs. 64.65 ± 22.64, P = 0.047 and 39.83 ± 9.88 vs. 46.43 ± 7.82, P = 0.015, respectively). Foreign body sensation was significantly lower in the LW group at day 120 (4.2% vs. 30.4 %, P = 0.023), as was sense of stiffness (P = 0.023). The sense of pull during activity was lower in the LW group at day 90 and 120 (P = 0.012 and P = 0.022, respectively). There was no recurrence or serious complication during follow-up. CONCLUSION: Partially-absorbable lightweight prosthetic mesh can be used for inguinal hernia repair safely and improve functional outcomes and quality of life after surgery.

Evaluating the predictability of PM10 grades in Seoul, Korea using a neural network model based on synoptic patterns.

As of November 2014, the Korean Ministry of Environment (KME) has been forecasting the concentration of particulate matter with diameters ≤ 10 µm (PM10) classified into four grades: low (PM10 ≤ 30 µg m-3), moderate (30 < PM10 ≤ 80 µg m-3), high (80 < PM10 ≤ 150 µg m-3), and very high (PM10 > 150 µg m-3). The KME operational center generates PM10 forecasts using statistical and chemistry-transport models, but the overall performance and the hit rate for the four PM10 grades has not previously been evaluated. To provide a statistical reference for the current air quality forecasting system, we have developed a neural network model based on the synoptic patterns of several meteorological fields such as geopotential height, air temperature, relative humidity, and wind. Hindcast of the four PM10 grades in Seoul, Korea was performed for the cold seasons (October-March) of 2001-2014 when the high and very high PM10 grades are frequently observed. Because synoptic patterns of the meteorological fields are distinctive for each PM10 grade, these fields were adopted and quantified as predictors in the form of cosine similarities to train the neural network model. Using these predictors in conjunction with the PM10 concentration in Seoul from the day before prediction as an additional predictor, an overall hit rate of 69% was achieved; the hit rates for the low, moderate, high, and very high PM10 grades were 33%, 83%, 45%, and 33%, respectively. Our findings also suggest that the synoptic patterns of meteorological variables are reliable predictors for the identification of the favorable conditions for each PM10 grade, as well as for the transboundary transport of PM10 from China. This evaluation of PM10 predictability can be reliably used as a statistical reference and further, complement to the current air quality forecasting system.

Persistent Bleeding Following a Stapled Hemorrhoidopexy.

A stapled hemorrhoidopexy (SH) is widely used for treatment of patients with grades III and IV hemorrhoids. The SH is easy to perform, is associated with less pain and allows early return to normal activities. However, complications, whether severe or not, have been reported. Here, we present the case of a female patient with persistent bleeding after a SH. The bleeding was caused by the formation of granulation tissue at the stapler line, diagnosed with sigmoidoscopy, and successfully treated via transanal excision (TAE) under spinal anesthesia. The biopsy showed inflammatory granulation tissue. After the TAE, her symptom was completely gone.

Clinical impact of atypical endoscopic features in rectal neuroendocrine tumors.

AIM: To validate the association between atypical endoscopic features and lymph node metastasis (LNM). METHODS: A total of 247 patients with rectal neuroendocrine tumors (NETs) were analyzed. Endoscopic images were reviewed independently by two endoscopists, each of whom classified tumors by sized and endoscopic features, such as shape, color, and surface change (kappa coefficient 0.76 for inter-observer agreement). All of patients underwent computed tomography scans of abdomen and pelvis for evaluation of LNM. Univariate and multivariate analyses were performed to identify the factors associated with LNM. Additionally, the association between endoscopic atypical features and immunohistochemical staining of tumors was analyzed. RESULTS: Of 247 patients, 156 (63.2%) were male and 15 (6.1%) were showed positive for LNM. On univariate analysis, tumor size (P < 0.001), shape (P < 0.001), color (P < 0.001) and surface changes (P < 0.001) were significantly associated with LNM. On multivariate analysis, tumor size (OR = 11.53, 95%CI: 2.51-52.93, P = 0.002) and atypical surface (OR = 27.44, 95%CI: 5.96-126.34, P < 0.001) changes were independent risk factors for LNM. The likelihood of atypical endoscopic features increased as tumor size increased. Atypical endoscopic features were associated with LNM in rectal NETs < 10 mm (P = 0.005) and 10-19 mm (P = 0.041) in diameter. Immunohistochemical staining showed that the rate of atypical endoscopic features was higher in non L-cell tumors. CONCLUSION: Atypical endoscopic features as well as tumor size are predictive factors of LNM in patients with rectal NETs.

The Clinical Features and Predictive Risk Factors for Reoperation in Patients With Perianal Crohn Diseases; A Multi-Center Study of a Korean Inflammatory Bowel Disease Study Group.

PURPOSE: Perianal lesions are common in Crohn disease, but their clinical course is unpredictable. Nevertheless, predicting the clinical course after surgery for perianal Crohn disease (PCD) is important because repeated operations may decrease patient's quality of life. The aim of this study was to predict the risk of reoperation in patients with PCD. METHODS: From September 1994 to February 2010, 377 patients with PCD were recruited in twelve major tertiary university-affiliated hospitals and two specialized colorectal hospitals in Korea. Data on the patient's demographics, clinical features, and surgical outcomes were analyzed. RESULTS: Among 377 patients, 227 patients were ultimately included in the study. Among the 227 patients, 64 patients underwent at least one reoperation. The median period of reoperation following the first perianal surgery was 94 months. Overall 3-year, 5-year, and 10-year cumulative rates of reoperation-free individuals were 68.8%, 61.2%, and 50.5%, respectively. In multivariate analysis (Cox-regression hazard model), reoperation was significantly correlated with an age of onset less than 20 years (hazard ratio [HR], 1.93; 95% confidence interval [CI], 1.07-3.48; P = 0.03), history of abdominal surgery (HR, 1.99; 95% CI, 1.08-3.64; P = 0.03), and the type of surgery. Among types of surgery, fistulotomy or fistulectomy was associated with a decreased incidence of reoperation in comparison with incision and drainage (HR, 0.19; 95% CI, 0.09-0.42; P < 0.001). CONCLUSION: Young age of onset and a history of abdominal surgery were associated with a high risk of reoperation for PCD, and the risk of reoperation were relatively low in fistulotomy or fistulectomy procedures.

Clinical Features of Tuberculous Versus Crohn's Anal Fistulas, in Korea.

BACKGROUND AND AIMS: In Western countries, tuberculous anal fistula may not be an issue because tuberculosis [TB] is not common, and this is a very rare form of extrapulmonary manifestation of TB. However in TB-endemic countries, careful diagnostic differentiation is required because the clinical features of TB anal fistula and Crohn's disease [CD] anal fistula are similar, with distinguishing features remaining unclear. We aimed to analyse the clinical features of TB versus CD anal fistulas. METHOD: Among 13872 patients who underwent anal fistula surgery from 2003 to 2014, 87 patients with TB fistulas and 116 patients with CD fistulas were included. Data on the annual incidence of TB and CD, as well as the clinical, pathological, ultrasonographic, colonoscopic and surgical data were analysed. RESULTS: Compared with CD, the TB group was older [median: 37 vs 22 years] and underlying chronic illness was more common [20.3% vs 2.6%]. In the TB group, 46 patients [59.7%] showed active or inactive pulmonary TB, and acid-fast bacilli and caseating granuloma were found in 56.3% and 62.1%, respectively. During colonoscopy, mucosal lesions were observed more frequently in CD [96.9% vs 16.9%]. CONCLUSIONS: TB anal fistula is clinically very similar to CD anal fistula. In Korea, the incidence of CD anal fistula has recently increased in prevalence, whereas the prevalence of TB anal fistula is decreasing but is still persistent. We recommend that clinicians should prepare for a possibility of TB as well as CD anal fistula in TB-endemic countries including Korea.

Iris-fixated phakic intraocular lens implantation after retinal detachment surgery: long-term clinical results.

PURPOSE: To assess the efficacy and safety of iris-fixated phakic intraocular lens (pIOL) implantation to correct myopia in eyes with previous retinal detachment (RD) surgery. SETTING: Department of Ophthalmology, Soonchunhyang University College of Medicine, Seoul, South Korea. DESIGN: Retrospective case series. METHODS: Patients having pIOL implantation in both eyes were enrolled. Eyes that had scleral buckling or encircling (RD group) and healthy fellow eyes (non-RD group) were evaluated over a 6-year follow-up. The corrected distance visual acuity (CDVA), endothelial cell density (ECD), intraoperative complications, and long-term complications were safety outcomes. Uncorrected distance visual acuity (UDVA), predictability, and stability of refraction were efficacy outcomes. RESULTS: The study comprised 34 eyes (17 patients). The mean postoperative CDVA and ECD were not significantly different between groups, and no patient lost CDVA. The rate of transient intraocular pressure spike was significantly higher in the RD group (P=.043). After 3 years and 6 years, the mean postoperative UDVA was 0.06 logMAR ± 0.09 (SD) and 0.08 ± 0.10 logMAR, respectively, in the RD group and 0.04 ± 0.08 logMAR and 0.04 ± 0.09 logMAR, respectively, in the non-RD group (P=.518 and P=.478, respectively). The rate of eyes within ±0.50 diopter of the desired refraction and the postoperative refraction was not significantly different between groups. No eye had vitreoretinal changes requiring secondary surgical intervention. CONCLUSION: Iris-fixated pIOL implantation corrected the myopic refractive error in patients who had scleral buckling or encircling surgery for RD with a high degree of efficacy, safety, and long-term stability. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Comparison of preoperative and postoperative ocular biometry in eyes with phakic intraocular lens implantations.

PURPOSE: To compare preoperative and postoperative ocular biometry in patients with iris-fixated phakic intraocular lens (pIOLs): Artisan and Artiflex. MATERIALS AND METHODS: This study included 40 eyes with Artisan and 36 eyes with Artiflex pIOL implants. Anterior chamber depth (ACD) and axial length (AL) were measured by applanation ultrasonography (A-scan) and partial coherence interferometry (IOLMaster) preoperatively and 3 months after pIOL implantation. RESULTS: ACD measurements after Artisan or Artiflex pIOL implantation were smaller than preoperative measurements. Specifically, the difference after Artisan pIOL implantation was -1.07 ± 0.17 mm by A-scan and -0.08 ± 0.08 mm by IOLMaster. The difference after Artiflex pIOL implantation was -1.31 ± 0.15 mm by A-scan and -0.05 ± 0.07 mm by IOLMaster. After Artisan pIOL implantation, differences in AL measurements by A-scan were insignificant (difference: -0.03 ± 0.15 mm), whereas postoperative AL measurements by IOLMaster were significantly longer than preoperative measurements (difference: 0.12 ± 0.07 mm). After Artiflex pIOL implantation, AL measurements by both A-scan and IOLMaster were significantly longer than preoperative measurements (difference: 0.09 ± 0.16 mm by A-scan and 0.07 ± 0.10 mm by IOLMaster). In the Artiflex group, differences in AL measurements by A-scan correlated with the central thickness of the Artiflex pIOL. CONCLUSION: ACD and AL measurements were influenced by iris-fixated phakic IOL implantation.

Endoscopic submucosal dissection for nonpedunculated submucosal invasive colorectal cancer: is it feasible?

BACKGROUND/AIMS: There have been no definite indications for additional surgical resection after endoscopic submucosal dissection (ESD) of submucosal invasive colorectal cancer (SICC). The aims of this study were to evaluate the feasibility of ESD for nonpedunculated SICC and to determine the need for subsequent surgery after ESD. PATIENTS AND METHODS: A total of 150 patients with nonpedunculated SICC in resected specimens after ESD were analyzed. Among them, 75 patients underwent subsequent surgery after ESD. Clinical outcomes of ESD and histopathological risk factors for lymph node (LN) metastasis were evaluated. RESULTS: The en-bloc resection and complete resection (R0) rates of ESD were 98% (147/150) and 95.3% (143/150), respectively. None of the patients had delayed bleeding after ESD. Perforations occurred in seven patients (4.7%), which were successfully treated by endoscopic clipping. After subsequent surgery for 75 patients, LN metastases were found in 10 cases (13.3%). The incidence of LN metastasis was significantly higher in tumors featuring submucosal invasion of at least 1500 µm, lymphovascular invasion, and tumor budding. Multivariate analysis showed that lymphovascular invasion (P=0.034) and tumor budding (P=0.015) were significantly associated with LN metastasis. Among the 150 patients, no local recurrence or distant metastasis was detected, except one patient with risk factors and who refused subsequent surgery, during the overall median follow-up of 34 months (range, 5-63 months). CONCLUSION: ESD is feasible and may be considered as an alternative treatment option for carefully selected cases of nonpedunculated SICC, provided that the appropriate histopathological curative criteria are fulfilled in completely resectable ESD specimens.

Rectal neuroendocrine and L-cell tumors: diagnostic dilemma and therapeutic strategy.

Rectal neuroendocrine tumors (NETs) are currently divided into L-cell and non-L-cell types. In the World Health Organization 2010 classification, L-cell tumors are defined as borderline, whereas non-L-cell tumors are considered to represent malignancies. To establish differential diagnostic criteria and therapeutic strategy, we investigated the pathologic features of rectal NETs associated with lymph node metastasis and the clinicopathologic significance of the L-cell phenotype. We analyzed 284 patients with rectal NETs. Factors, including T stage, mitosis, histologic pattern, lymphatic invasion, tumor border, and lymph node metastasis, were retrospectively evaluated. We also evaluated tumor immunoreactivity for L-cell markers, including glucagon-like peptide 1, pancreatic peptide, and peptide YY, in 240 cases. L-cell immunoreactivity was detected in 189 of 240 NETs (79%). Of the factors evaluated, only age and the frequency of lymphatic invasion were significantly different between patients with L-cell and non-L-cell tumors. Of the 284 patients, 18 (6.3%) had lymph node metastases. Lymphatic invasion and T stage were independent risk factors for lymph node metastasis. Subgroup analysis based on tumor size showed lymph node metastasis in 0%, 4%, 24%, and 100% of patients with NETs with a size of <5, 5 to 9, 10 to 14, and ≥ 15 mm, respectively. Depth of tumor invasion, lymphatic invasion, and mitosis were correlated with tumor size (P<0.0001). In conclusion, L-cell phenotype alone does not guarantee favorable biological characteristics. The clinical management of rectal NETs should depend on tumor size. Careful pathologic examination of lymphatic invasion is necessary.

Can endoscopic submucosal dissection technique be an alternative treatment option for a difficult giant (≥ 30 mm) pedunculated colorectal polyp?

BACKGROUND: Snare polypectomy of a giant pedunculated colorectal polyp is sometimes technically demanding, and, therefore, piecemeal resection is inevitable, despite the relative risk of invasive cancer and postpolypectomy bleeding. OBJECTIVE: The aim of this study was to evaluate the efficacy and safety of endoscopic submucosal dissection in comparison with conventional snare polypectomy for giant pedunculated polyps DESIGN AND SETTINGS: We retrospectively reviewed the clinical outcomes and complications of endoscopic polypectomy for giant pedunculated polyps from October 2006 to November 2011. PATIENTS: All the patients who underwent endoscopic submucosal dissection (n = 23) or snare polypectomy (n = 20) for pedunculated polyps ≥ 3 cm were enrolled consecutively. In the case of a giant pedunculated polyp with 1) poor visualization of the stalk, 2) technical difficulties in snare positioning for en bloc resection, or 3) need for trimming of the head, we did not attempt piecemeal snare polypectomy, and we performed endoscopic submucosal dissection instead. (These were arbitrarily defined as "difficult" giant pedunculated polyps.) MAIN OUTCOME MEASURES: Data on the patient's demography, endoscopic and histopathologic findings, clinical outcomes, and complications were analyzed. RESULTS: Among the 43 giant pedunculated polyps, 23 polyps were defined as "difficult" polyps and were removed with endoscopic submucosal dissection. Subpedunculated (stalk <1 cm) type was more common in the "difficult" polyp group (p = 0.01). The overall incidence of cancer was 18.6% (8/43). En bloc resection rates were 100% (23/23) in the endoscopic submucosal dissection group and 90% (18/20) in the snare polypectomy group. The procedure times of snare polypectomy and endoscopic submucosal dissection group did not differ significantly (41.7 ± 13.7 minutes vs 44.9 ± 35.6 minutes, p = 0.70). Postpolypectomy bleeding was noted in 1 case (4.3%) in the endoscopic submucosal dissection group and in 3 cases (15%) in the snare polypectomy group. CONCLUSIONS: Endoscopic submucosal dissection, as well as the snare polypectomy for giant pedunculated polyps, appeared to be effective without major complications and can be an alternative option to achieve en bloc resection, particularly for difficult cases, such as giant subpedunculated polyps.

Endoscopic submucosal dissection for colorectal tumors--1,000 colorectal ESD cases: one specialized institute's experiences.

PURPOSE: Endoscopic submucosal dissection (ESD) is a very useful endoscopic technique, making it possible to perform en bloc resection regardless of lesion size. Since the introduction of ESD at our hospital, we have performed 1,000 colorectal ESDs during 56 months. The purpose of this study was to evaluate the clinical outcomes of our colorectal ESD experience and to access the efficacy and safety of colorectal ESD. METHODS: Between October 2006 and August 2011, we performed ESD on 1,000 consecutive colorectal tumors in 966 patients. We evaluated the clinical outcomes of all said cases. RESULTS: The mean resected tumor size was 24.1 ± 13.3 (3-145) mm. Our overall endoscopic en bloc resection rate was 97.5% (975/1,000), and our R0 resection rate was 91.2% (912/1,000) respectively. Our perforation rate was 5.3% (53/1,000). Of these 53 perforations, 50 cases were treated through conservative management with/without endoscopic clipping, whereas the remaining 3 patients received laparoscopic operation. Pathological examination showed adenocarcinoma in 37.2% of cases (372/1,000) and neuroendocrine tumors in 11.2% (112/1,000). We recommended additional radical surgery to 82 patients who had a risk of lymph node metastasis. Follow-up colonoscopies were performed on 722 patients. During the median follow-up period of 13 (1-62) months, there were three recurrences (0.4%). CONCLUSIONS: ESD is technically difficult, with a substantial risk of perforation. However, ESD enabled en bloc resection and pathologically complete resection of large colorectal epithelial tumors and submucosal tumors. As experience with the technique increases, ESD may gradually replace piecemeal endoscopic mucosal resection and radical colon resection in the treatment of colorectal tumors.