Ultrasound transmural healing correlates with higher adalimumab drug concentration in Crohn's disease only in the short-term.

BACKGROUND: Anti-TNF drugs have revolutionized the treatment of Crohn's disease (CD) and have set new therapeutic targets. A direct correlation between anti-TNF trough levels and endoscopic healing in IBD patients has been established, but the association between drug levels and transmural healing assessed by ultrasound is not yet clearly defined. AIMS: To evaluate the correlation between the serum concentration of adalimumab (ADA) and sonographic transmural healing in CD patients at different times during the follow-up of patients. METHODS: In this retrospective, cross-sectional study all patients with CD who were undergoing treatment with ADA in our center were included. Intestinal ultrasound (IUS) was performed before the initiation of the drug and for response monitoring. ADA serum-through levels were compared between patients with and without transmural healing at different periods of time. RESULTS: 92 patients were included, all patients showed signs of inflammatory activity in the baseline IUS. In the IUS monitoring of the response to ADA, 34 (34.8%) patients presented transmural healing. Among patients in the first year of treatment, those with sonographic healing showed higher median levels than patients without transmural healing (12.0 µg/mL vs. 9.3 µg/mL, respectively; p= 0.007). There was no correlation found between adalimumab levels and sonographic healing in patients undergoing treatment for over a year. CONCLUSIONS: Higher adalimumab through levels were corelated with transmural healing with ultrasound during the first year of treatment. This correlation was not found after one year of treatment.

Artificial intelligence for dysplasia detection during surveillance colonoscopy in patients with ulcerative colitis: A cross-sectional, non-inferiority, diagnostic test comparison study.

BACKGROUND AND STUDY AIM: High-definition virtual chromoendoscopy, along with targeted biopsies, is recommended for dysplasia surveillance in ulcerative colitis patients at risk for colorectal cancer. Computer-aided detection (CADe) systems aim to improve colonic adenoma detection, however their efficacy in detecting polyps and adenomas in this context remains unclear. This study evaluates the CADe Discovery™ system's effectiveness in detecting colonic dysplasia in ulcerative colitis patients at risk for colorectal cancer. PATIENTS AND METHODS: A prospective cross-sectional, non-inferiority, diagnostic test comparison study was conducted on ulcerative colitis patients undergoing colorectal cancer surveillance colonoscopy between January 2021 and April 2021. Patients underwent virtual chromoendoscopy (VCE) with iSCAN 1 and 3 with optical enhancement. One endoscopist, blinded to CADe Discovery™ system results, examined colon sections, while a second endoscopist concurrently reviewed CADe images. Suspicious areas detected by both techniques underwent resection. Proportions of dysplastic lesions and patients with dysplasia detected by VCE or CADe were calculated. RESULTS: Fifty-two patients were included, and 48 lesions analyzed. VCE and CADe each detected 9 cases of dysplasia (21.4% and 20.0%, respectively; p=0.629) in 8 patients and 7 patients (15.4% vs. 13.5%, respectively; p=0.713). Sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy for dysplasia detection using VCE or CADe were 90% and 90%, 13% and 5%, 21% and 2%, 83% and 67%, and 29.2% and 22.9%, respectively. CONCLUSIONS: The CADe Discovery™ system shows similar diagnostic performance to VCE with iSCAN in detecting colonic dysplasia in ulcerative colitis patients at risk for colorectal cancer.

Effect of the SARS-CoV-2 pandemic on colorectal cancer diagnosis and prognosis.

BACKGROUND AND STUDY AIMS: Our aim was to determine the impact of the SARS-CoV-2 pandemic on the diagnosis and prognosis of colorectal cancer (CRC). PATIENTS AND METHODS: This prospective cohort study included individuals diagnosed with CRC between March 13, 2019 and June 20, 2021 across 21 Spanish hospitals. Two time periods were compared: prepandemic (from March 13, 2019 to March 13, 2020) and pandemic (from March 14, 2020 to June 20, 2021, lockdown period and 1 year after lockdown). RESULTS: We observed a 46.9% decrease in the number of CRC diagnoses (95% confidence interval (CI): 45.1%-48.7%) during the lockdown and 29.7% decrease (95% CI: 28.1%-31.4%) in the year after the lockdown. The proportion of patients diagnosed at stage I significantly decreased during the pandemic (21.7% vs. 19.0%; p = 0.025). Centers that applied universal preprocedure SARS-CoV-2 PCR testing experienced a higher reduction in the number of colonoscopies performed during the pandemic post-lockdown (34.0% reduction; 95% CI: 33.6%-34.4% vs. 13.7; 95% CI: 13.4%-13.9%) and in the number of CRCs diagnosed (34.1% reduction; 95% CI: 31.4%-36.8% vs. 26.7%; 95% CI: 24.6%-28.8%). Curative treatment was received by 87.5% of patients diagnosed with rectal cancer prepandemic and 80.7% of patients during the pandemic post-lockdown period (p = 0.002). CONCLUSIONS: The COVID-19 pandemic has led to a decrease in the number of diagnosed CRC cases and in the proportion of stage I CRC. The reduction in the number of colonoscopies and CRC diagnoses was higher in centers that applied universal SARS-CoV-2 PCR screening before colonoscopy. In addition, the COVID-19 pandemic has affected curative treatment of rectal cancers.

Fecal immunochemical test for hemoglobin versus fecal calprotectin to monitor endoscopic activity in inflammatory bowel disease.

AIM: endoscopy identifies inflammatory activity, however, it is an unpleasant test and is not always accessible. The aim of the study was to compare the usefulness of quantitative fecal immunochemical test (FIT) versus fecal calprotectin (FC) to determine endoscopic activity in patients with inflammatory bowel disease (IBD). METHODS: cross-sectional prospective observational study. The stool samples were collected within three days before starting the preparation for the colonoscopy. We used the Mayo index for ulcerative colitis (UC) and the simplified endoscopic index for Crohn's disease (CD). Mucosal healing (MH) was defined as the score 0 points in each of the endoscopic indices. RESULTS: eighty-four patients were included, 40 (47.6 %) with UC. In patients with IBD, FIT and FC showed a significant correlation with the presence of inflammatory activity/MH on endoscopy, with no statistically significant differences between the two receiver-operating characteristic (ROC) curves. Both tests improved their diagnostic performance when assessing patients with UC; the Spearman correlations between FIT and FC and endoscopic inflammatory activity were r = 0.6 (p = 0.0001) and r = 0.7 (p = 0.0001), respectively. In Crohn's disease, the diagnostic utility of both tests was lower. CONCLUSIONS: FIT is an alternative to monitor endoscopic activity among ulcerative colitis patients. In Crohn's disease, more studies are needed to determine the role of fecal biomarkers.

Fecal immunochemical test for hemoglobin versus fecal calprotectin to monitor endoscopic activity in inflammatory bowel disease

Aim: endoscopy identifies inflammatory activity, however, it is an unpleasant test and is not always accessible. The aim of the study was to compare the usefulness of quantitative fecal immunochemical test (FIT) versus fecal calprotectin (FC) to determine endoscopic activity in patients with inflammatory bowel disease (IBD). Methods: cross-sectional prospective observational study. The stool samples were collected within three days before starting the preparation for the colonoscopy. We used the Mayo index for ulcerative colitis (UC) and the simplified endoscopic index for Crohn’s disease (CD). Mucosal healing (MH) was defined as the score 0 points in each of the endoscopic indices. Results: eighty-four patients were included, 40 (47.6 %) with UC. In patients with IBD, FIT and FC showed a significant correlation with the presence of inflammatory activity/MH on endoscopy, with no statistically significant differences between the two receiver-operating characteristic (ROC) curves. Both tests improved their diagnostic performance when assessing patients with UC; the Spearman correlations between FIT and FC and endoscopic inflammatory activity were r = 0.6 (p = 0.0001) and r = 0.7 (p = 0.0001), respectively. In Crohn’s disease, the diagnostic utility of both tests was lower. Conclusions: FIT is an alternative to monitor endoscopic activity among ulcerative colitis patients. In Crohn’s disease, more studies are needed to determine the role of fecal biomarkers. (AU)

Recomendaciones de la Sociedad Valenciana de Patología Digestiva sobre uso de consultas no presenciales y telemedicina / Recommendations of the Valencian Society of Digestive Pathology for the use of telemedicine and non-contact consultations

La pandemia COVID-19 ha supuesto un cambio cualitativo en el modo de atender a los pacientes en consultas ambulatorias. La necesidad de toma de medidas de aislamiento social como prevención para el contagio por el SARS-CoV-2 ha obligado al uso de consultas telemáticas y telefónicas en la mayoría de unidades médicas y quirúrgicas. La especialidad de Aparato Digestivo, por las características de sus pacientes y el apoyo frecuente en técnicas complementarias para el diagnóstico, es especialmente adecuada para realizar consultas no presenciales. En este documento se plantean una serie de recomendaciones que pueden servir como guía para el establecimiento o mejora de consultas no presenciales de Medicina Digestiva.(AU)

The COVID-19 pandemic has meant a qualitative change in the way patients are treated in outpatient clinics. The need to take measures of social isolation as prevention for contagion by the new coronavirus has forced the use of telematic and telephone consultations in most medical and surgical units. The specialty of digestive medicine, due to the characteristics of its patients and frequent support in complementary techniques for diagnosis, is especially suitable for the use of non-contact consultations. In this document a series of recommendations are proposed that can serve as a guide for the establishment or improvement of non-face-to-face digestive medicine consultations.(AU)

Adherence to endoscopic surveillance for advanced lesions and colorectal cancer in inflammatory bowel disease: an AEG and GETECCU collaborative cohort study.

BACKGROUND AND AIMS: Patients with colonic inflammatory bowel disease (IBD) have a high risk of colorectal cancer (CRC). Current guidelines recommend endoscopic surveillance, yet epidemiological studies show poor compliance. The aims of our study were to analyse adherence to endoscopic surveillance, its impact on advanced colorectal lesions, and risk factors of non-adherence. METHODS: A retrospective multicentre study of IBD patients with criteria for CRC surveillance, diagnosed between 2005 and 2008 and followed up to 2020, was performed. Following European guidelines, patients were stratified into risk groups and adherence was considered when surveillance was performed according to the recommendations (±1 year). Cox-proportional regression analyses were used to compare the risk of lesions. p-values below 0.05 were considered significant. RESULTS: A total of 1031 patients (732 ulcerative colitis, 259 Crohn's disease and 40 indeterminate colitis; mean age of 36 ± 15 years) were recruited from 25 Spanish centres. Endoscopic screening was performed in 86% of cases. Adherence to guidelines was 27% (95% confidence interval, CI = 24-29). Advanced lesions and CRC were detected in 38 (4%) and 7 (0.7%) patients respectively. Adherence was associated with increased detection of advanced lesions (HR = 3.59; 95% CI = 1.3-10.1; p = 0.016). Risk of delay or non-performance of endoscopic follow-up was higher as risk groups increased (OR = 3.524; 95% CI = 2.462-5.044; p < 0.001 and OR = 4.291; 95%CI = 2.409-7.644; p < 0.001 for intermediate- and high- vs low-risk groups). CONCLUSIONS: Adherence to endoscopic surveillance allows earlier detection of advanced lesions but is low. Groups at higher risk of CRC are associated with lower adherence.

Recommendations of the Valencian Society of Digestive Pathology for the use of telemedicine and non-contact consultations. / Recomendaciones de la Sociedad Valenciana de Patología Digestiva sobre uso de consultas no presenciales y telemedicina.

The COVID-19 pandemic has meant a qualitative change in the way patients are treated in outpatient clinics. The need to take measures of social isolation as prevention for contagion by the new coronavirus has forced the use of telematic and telephone consultations in most medical and surgical units. The specialty of digestive medicine, due to the characteristics of its patients and frequent support in complementary techniques for diagnosis, is especially suitable for the use of non-contact consultations. In this document a series of recommendations are proposed that can serve as a guide for the establishment or improvement of non-face-to-face digestive medicine consultations.

Virtual chromoendoscopy with iSCAN as an alternative method to dye-spray chromoendoscopy for dysplasia detection in long-standing colonic inflammatory bowel disease: a case-control study.

OBJECTIVE: Patients with long-standing colonic inflammatory bowel disease (cIBD) are at increased risk of developing colorectal cancer (CRC). Dye-spray chromoendoscopy (DCE) with targeted biopsies is the preferred technique for surveillance of dysplasia. Virtual chromoendoscopy (VCE) are arising to improve detection rates and adherence to surveillance guidelines, although its role is not yet well defined. The purpose of this study is to assess the effectiveness of VCE with iSCAN as an alternative method for dysplasia detection in cIBD. METHODS: Retrospective case-control study with 191 patients included, 98 in the DCE (Indigo carmine) group and 93 in the VCE (iSCAN, twin-mode 1-3) group. The dysplasia detection and the exploration time were analysed. A logistic regression analysis was performed to ascertain the factors related to colonic dysplasia. RESULTS: A total of 44 dysplastic lesions were detected in 21 (11%) patients. No differences were found in the per lesion and the per patient analysis (dysplastic versus non-dysplastic). Median withdrawal time was shorter in the VCE group than in the DCE group (9 min versus 14 min; p < .001). Location of lesions in the right colon was independently associated with an increased risk for colonic dysplasia (OR = 4.04, 95%CI 1.11-14.65; p = .034) after adjusting for age at inclusion, age at diagnosis, high risk for CRC and Kudo pit pattern. CONCLUSIONS: VCE with iSCAN presents a similar diagnostic performance to conventional DCE in the detection of colonic dysplasia in patients with long-standing cIBD. Furthermore, VCE with iSCAN is a less time-consuming surveillance alternative to DCE.

Hemostatic spray powder TC-325 for GI bleeding in a nationwide study: survival and predictors of failure via competing risks analysis.

BACKGROUND AND AIMS: TC-325 (Hemospray, Cook Medical, Winston-Salem, NC) is an inorganic hemostatic powder recently approved by the U.S. Food and Drug Administration. This study aimed to examine the effectiveness, safety, and predictors of TC-325 failure in a large real-life cohort. METHODS: This was a retrospective study conducted at 21 Spanish centers. All patients treated with TC-325 until September 2018 were included. The primary outcome was treatment failure, defined as failed intraprocedural hemostasis or recurrent bleeding within the first 30 postprocedural days. Secondary outcomes included safety and survival. Risk and predictors of failure were assessed via competing-risk models. RESULTS: The cohort comprised 261 patients, of whom 219 (83.9%) presented with upper gastrointestinal bleeding (GIB). The most common causes were peptic ulcer (28%), malignancy (18.4%), and therapeutic endoscopy-related GIB (17.6%). TC-325 was used as rescue therapy in 191 (73.2%) patients. The rate of intraprocedural hemostasis was 93.5% (95% confidence interval [CI], 90%-96%). Risks of TC-325 failure at postprocedural days 3, 7, and 30 were 21.1%, 24.6%, and 27.4%, respectively. On multivariate analysis, spurting bleeding (P = .004), use of vasoactive drugs (P = .02), and hypotension (P = .008) were independent predictors of failure. Overall 30-day survival was 81.9% (95% CI, 76%-86%) and intraprocedural hemostasis was associated with a better prognosis (adjusted hazard ratio, 0.29; P = .006). Two severe adverse events were noted. CONCLUSION: TC-325 was safe and effective for intraprocedural hemostasis in more than 90% of patients, regardless of the cause or site of bleeding and its use as rescue therapy. In this high-risk cohort treated with TC-325, the 30-day failure rate exceeded 25% and was highest with spurting bleeding or hemodynamic instability.

Determinants of Severity in Acute Pancreatitis: A Nation-wide Multicenter Prospective Cohort Study.

OBJECTIVE: The aim of this study was to compare and validate the different classifications of severity in acute pancreatitis (AP) and to investigate which characteristics of the disease are associated with worse outcomes. SUMMARY OF BACKGROUND DATA: AP is a heterogeneous disease, ranging from uneventful cases to patients with considerable morbidity and high mortality rates. Severity classifications based on legitimate determinants of severity are important to correctly describe the course of disease. METHODS: A prospective multicenter cohort study involving patients with AP from 23 hospitals in Spain. The Atlanta Classification (AC), Revised Atlanta Classification (RAC), and Determinant-based Classification (DBC) were compared. Binary logistic multivariate analysis was performed to investigate independent determinants of severity. RESULTS: A total of 1655 patients were included; 70 patients (4.2%) died. RAC and DBC were equally superior to AC for describing the clinical course of AP. Although any kind of organ failure was associated with increased morbidity and mortality, persistent organ failure (POF) was the most significant determinant of severity. All local complications were associated with worse outcomes. Infected pancreatic necrosis correlated with high morbidity, but in the presence of POF, it was not associated to higher mortality when compared with sterile necrotizing pancreatitis. Exacerbation of previous comorbidity was associated with increased morbidity and mortality. CONCLUSION: The RAC and DBC both signify an advance in the description and differentiation of AP patients. Herein, we describe the complications of the disease independently associated to morbidity and mortality. Our findings are valuable not only when designing future studies on AP but also for the improvement of current classifications.

Real-life chromoendoscopy for neoplasia detection and characterisation in long-standing IBD.

OBJECTIVE: Outside clinical trials, the effectiveness of chromoendoscopy (CE) for long-standing IBD surveillance is controversial. We aimed to assess the effectiveness of CE for neoplasia detection and characterisation, in real-life. DESIGN: From June 2012 to 2014, patients with IBD were prospectively included in a multicentre cohort study. Each colonic segment was evaluated with white light followed by 0.4% indigo carmine CE. Specific lesions' features were recorded. Optical diagnosis was assessed. Dysplasia detection rate between expert and non-expert endoscopists and learning curve were ascertained. RESULTS: Ninety-four (15.7%) dysplastic (1 cancer, 5 high-grade dysplasia, 88 low-grade dysplasia) and 503 (84.3%) non-dysplastic lesions were detected in 350 patients (47% female; mean disease duration: 17 years). Colonoscopies were performed with standard definition (41.5%) or high definition (58.5%). Dysplasia miss rate with white light was 40/94 (57.4% incremental yield for CE). CE-incremental detection yield for dysplasia was comparable between standard definition and high definition (51.5% vs 52.3%, p=0.30). Dysplasia detection rate was comparable between expert and non-expert (18.5% vs 13.1%, p=0.20). No significant learning curve was observed (8.2% vs 14.2%, p=0.46). Sensitivity, specificity, and positive and negative predictive values for dysplasia optical diagnosis were 70%, 90%, 58% and 94%, respectively. Endoscopic characteristics predictive of dysplasia were: proximal location, loss of innominate lines, polypoid morphology and Kudo pit pattern III-V. CONCLUSIONS: CE presents a high diagnostic yield for neoplasia detection, irrespectively of the technology and experience available in any centre. In vivo, CE optical diagnosis is highly accurate for ruling out dysplasia, especially in expert hands. Lesion characteristics can aid the endoscopist for in situ therapeutic decisions. TRIAL REGISTRATION NUMBER: NCT02543762.

Chemoprevention of polyp recurrence with curcumin followed by silibinin in a case of multiple colorectal adenomas

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Chemoprevention of polyp recurrence with curcumin followed by silibinin in a case of multiple colorectal adenomas.

Chemoprevention is a practical approach to reduce the risk of various cancers including colorectal cancer (CRC). The goal is to reduce the incidence of pre-neoplastic adenomatous polyps and prevent its progression to CRC. Curcumin and silibinin prevent intestinal polyp formation in mice. Curcumin sensitizes silymarin to exert synergistic anticancer activity in colon cancer cells. Patients presenting with multiple colorectal adenomatous polyps (MCRA) have a high lifetime risk for CRC. We present a 57-year-old man with MCRA, without deleterious germline APC or MYH mutations. Our patient had 54 polyps in the first colonoscopy, most of 3 to 8 mm and one of 20 mm with high grade dysplasia / adenocarcinoma. Four subsequent colonoscopies showed continuous development of adenomatous polyps treated by polypectomy for the most part and some with heat. After the treatment with curcumin for 3 months and a half followed by silibinin for 9 months, we find many less polyps than in the previous colonoscopies, going from the finding of 40 adenomas of 3-6 mm in the pre-treatment colonoscopy to 3 polyps after treatment.

Papel del digestólogo en el manejo del paciente obeso / Role of the gastroenterologist in the management of the obese patient

La obesidad es una enfermedad con una elevada prevalencia a nivel mundial en la que el digestólogo puede tener una labor importante. Por una parte, algunas enfermedades digestivas son más frecuentes en este grupo de pacientes y es posible que sea necesario evaluarlos antes de la cirugía. Por otra, la cirugía bariátrica puede presentar complicaciones digestivas a corto y largo plazo en las que sea imprescindible nuestra actuación. Además, no podemos olvidar el papel que el tratamiento endoscópico puede tener en la pérdida de peso. El objetivo de la presente revisión es destacar el papel del digestólogo en el manejo del paciente obeso candidato y/o sometido a tratamiento quirúrgico o endoscópico de la obesidad (AU)

Abstract Obesity is a highly prevalent disease worldwide, and one in which gastroenterologists can play an important role. Some digestive diseases are more common in obese patients, and preoperative evaluation may be required in some cases. Additionally, bariatric surgery can lead to digestive complications in the short and long term that require intervention, and endoscopic treatment can be an important factor in weight loss. The aim of this review is to highlight the role of the gastroenterologist in the management of obese patients who are either scheduled for or have undergone surgical or endoscopic treatment for obesity (AU)

Role of the gastroenterologist in the management of the obese patient. / Papel del digestólogo en el manejo del paciente obeso.

Obesity is a highly prevalent disease worldwide, and one in which gastroenterologists can play an important role. Some digestive diseases are more common in obese patients, and preoperative evaluation may be required in some cases. Additionally, bariatric surgery can lead to digestive complications in the short and long term that require intervention, and endoscopic treatment can be an important factor in weight loss. The aim of this review is to highlight the role of the gastroenterologist in the management of obese patients who are either scheduled for or have undergone surgical or endoscopic treatment for obesity.

Diagnosis, treatment and long-term outcomes of autoimmune pancreatitis in Spain based on the International Consensus Diagnostic Criteria: A multi-centre study.

OBJECTIVES: Autoimmune pancreatitis (AIP) is a form of chronic pancreatitis that has been reported worldwide for the last two decades. The aim of this study is to analyse the clinical profile of patients from Spain with AIP, as well as treatments, relapses and long-term outcomes. METHODS: Data from 59 patients with suspected AIP that had been diagnosed in 15 institutions are retrospectively analysed. Subjects are classified according to the International Consensus Diagnostic Criteria (ICDC). Patients with type 1 AIP (AIP1) and type 2 AIP (AIP2) are compared. Kaplan-Meier methodology is used to estimate the overall survival without relapses. RESULTS: Fifty-two patients met ICDC, 45 patients were AIP1 (86.5%). Common manifestations included abdominal pain (65.4%) and obstructive jaundice (51.9%). Diffuse enlargement of pancreas was present in 51.0%; other organ involvement was present in 61.5%. Serum IgG4 increased in 76.7% of AIP1 patients vs. 20.0% in AIP2 (p = 0.028). Tissue specimens were obtained in 76.9%. Initial successful treatment with steroids or surgery was achieved in 79.8% and 17.3%, respectively. Maintenance treatment was given in 59.6%. Relapses were present in 40.4% of AIP1, with a median of 483 days. Successful long-term remission was achieved in 86.4%. CONCLUSIONS: AIP1 is the most frequent form of AIP in Spain in our dataset. Regularly, ICDC allows AIP diagnosis without the need for surgery. Steroid and chirurgic treatments were effective and safe in most patients with AIP, although maintenance was required many times because of their tendency to relapse. Long-term serious consequences were uncommon.

Density, spatial distribution and mortality rate of the sea urchin Diadema mexicanum (Diadematoida: Diadematidae) at two reefs of Bahías de Huatulco, Oaxaca, Mexico / Densidad, distribución espacial y tasa de mortalidad de Diadema mexicanum (Diadematoida: Diadematidae) en dos arrecifes de Bahías de Huatulco, Oaxaca, México

Abstract Diadema mexicanum, a conspicuous inhabitant along the Mexican Pacific coast, is a key species for the dynamics of coral reefs; nevertheless, studies on population dynamics for this species are scarce. Monthly sampling was carried out between April 2008 and March 2009 at Isla Montosa and La Entrega, Oaxaca, Mexico using belt transects. Population density was estimated as well as abundance using Zippin's model. The relationship of density with sea-bottom temperature, salinity, pH, and pluvial precipitation was analyzed using a step by step multiple regression analysis. Spatial distribution was analyzed using Morisita's, Poisson and negative binomial models. Natural mortality rate was calculated using modified Berry's model. Mean density was 3.4 ± 0.66 ind·m-2 in La Entrega and 1.2 ± 0.4 ind·m-2 in Isla Montosa. Abundance of D. mexicanum in La Entrega was 12166 ± 25 individuals and 2675 ± 33 individuals in Isla Montosa. In Isla Montosa there was a positive relationship of density with salinity and negative with sea-bottom temperature, whereas in La Entrega there was not a significant relationship of density with any recorded environmental variable. Monthly mortality rate was 0.10 in La Entrega and 0.15 in Isla Montosa. Spatial distribution pattern was aggregated for both localities during the sampling period with oscillations in the intensity of aggregation. Higher density and abundance, and a low mortality rate, indicate better conditions for the population of D. mexicanum in La Entrega, contrasting with those of Isla Montosa where apparently there are more stressful conditions associated to stronger oceanographic conditions and a higher sedimentation rate resulting from the proximity of the Copalita River. Rev. Biol. Trop. 63 (Suppl. 2): 173-182. Epub 2015 June 01.

Resumen . Diadema mexicanum es un habitante conspicuo de las costas del Pacífico Mexicano y una especie clave en los arrecifes de coral, sin embargo son escasos los estudios acerca de la dinámica poblacional de esta especie. En el presente trabajo se muestreó mensualmente de abril 2008 a marzo 2009 en Isla Montosa y La Entrega usando transectos de banda. Se estimó la densidad poblacional, así como la abundancia mediante el modelo de Zippin. Se evaluó la relación entre la variación mensual de la densidad y la temperatura, salinidad, pH y precipitación pluvial usando un análisis de regresión lineal múltiple paso a paso. La distribución espacial se analizó con los modelos de Morisita, Poisson y Binomial Negativa. Se calculó la tasa de mortalidad natural usando el modelo de Berry modificado. La densidad media fue 3.4 ± 0.66 ind m-2 en La Entrega y 1.2 ± 0.4 ind m-2 en Isla Montosa. La abundancia en La Entrega fue 12 166 ± 25 individuos y 2 675 ± 33 individuos en Isla Montosa. Se registró una relación positiva de la densidad con la salinidad y negativa con la temperatura en Isla Montosa, mientras que en La Entrega ninguna variable ambiental se relacionó significativamente con la densidad. La distribución espacial fue agregada en ambas localidades con oscilaciones en la intensidad de agregación. La mortalidad mensual fue 0.1 en La Entrega y 0.15 en Isla Montosa. Los resultados indican mejores condiciones para la población de D. mexicanum en La Entrega en comparación con Isla Montosa, donde las condiciones oceanográficas son más severas y la tasa de sedimentación es más alta, asociada a la cercanía del Río Copalita.