Colonoscopy versus fecal immunochemical testing in colorectal-cancer screening.

BACKGROUND: Colonoscopy and fecal immunochemical testing (FIT) are accepted strategies for colorectal-cancer screening in the average-risk population. METHODS: In this randomized, controlled trial involving asymptomatic adults 50 to 69 years of age, we compared one-time colonoscopy in 26,703 subjects with FIT every 2 years in 26,599 subjects. The primary outcome was the rate of death from colorectal cancer at 10 years. This interim report describes rates of participation, diagnostic findings, and occurrence of major complications at completion of the baseline screening. Study outcomes were analyzed in both intention-to-screen and as-screened populations. RESULTS: The rate of participation was higher in the FIT group than in the colonoscopy group (34.2% vs. 24.6%, P<0.001). Colorectal cancer was found in 30 subjects (0.1%) in the colonoscopy group and 33 subjects (0.1%) in the FIT group (odds ratio, 0.99; 95% confidence interval [CI], 0.61 to 1.64; P=0.99). Advanced adenomas were detected in 514 subjects (1.9%) in the colonoscopy group and 231 subjects (0.9%) in the FIT group (odds ratio, 2.30; 95% CI, 1.97 to 2.69; P<0.001), and nonadvanced adenomas were detected in 1109 subjects (4.2%) in the colonoscopy group and 119 subjects (0.4%) in the FIT group (odds ratio, 9.80; 95% CI, 8.10 to 11.85; P<0.001). CONCLUSIONS: Subjects in the FIT group were more likely to participate in screening than were those in the colonoscopy group. On the baseline screening examination, the numbers of subjects in whom colorectal cancer was detected were similar in the two study groups, but more adenomas were identified in the colonoscopy group. (Funded by Instituto de Salud Carlos III and others; ClinicalTrials.gov number, NCT00906997.).

Rate of detection of advanced neoplasms in proximal colon by simulated sigmoidoscopy vs fecal immunochemical tests.

BACKGROUND & AIMS: We compared the ability of biennial fecal immunochemical testing (FIT) and one-time sigmoidoscopy to detect colon side-specific advanced neoplasms in a population-based, multicenter, nationwide, randomized controlled trial. METHODS: We identified asymptomatic men and women, 50-69 years old, through community health registries and randomly assigned them to groups that received a single colonoscopy examination or biennial FIT. Sigmoidoscopy yield was simulated from results obtained from the colonoscopy group, according to the criteria proposed in the UK Flexible Sigmoidoscopy Trial for colonoscopy referral. Patients who underwent FIT and were found to have ≥75 ng hemoglobin/mL were referred for colonoscopy. Data were analyzed from 5059 subjects in the colonoscopy group and 10,507 in the FIT group. The main outcome was rate of detection of any advanced neoplasm proximal to the splenic flexure. RESULTS: Advanced neoplasms were detected in 317 subjects (6.3%) in the sigmoidoscopy simulation group compared with 288 (2.7%) in the FIT group (odds ratio for sigmoidoscopy, 2.29; 95% confidence interval, 1.93-2.70; P = .0001). Sigmoidoscopy also detected advanced distal neoplasia in a higher percentage of patients than FIT (odds ratio, 2.61; 95% confidence interval, 2.20-3.10; P = .0001). The methods did not differ significantly in identifying patients with advanced proximal neoplasms (odds ratio, 1.17; 95% confidence interval, 0.78-1.76; P = .44). This was probably due to the lower performance of both strategies in detecting patients with proximal lesions (sigmoidoscopy detected these in 19.1% of patients and FIT in 14.9% of patients) vs distal ones (sigmoidoscopy detected these in 86.8% of patients and FIT in 33.5% of patients). Sigmoidoscopy, but not FIT, detected proximal lesions in lower percentages of women (especially those 50-59 years old) than men. CONCLUSIONS: Sigmoidoscopy and FIT have similar limitations in detecting advanced proximal neoplasms, which depend on patients' characteristics; sigmoidoscopy underperforms for women 50-59 years old. Screening strategies should be designed on the basis of target population to increase effectiveness and cost-effectiveness. ClinicalTrials.gov number: NCT00906997.

Participation and detection rates by age and sex for colonoscopy versus fecal immunochemical testing in colorectal cancer screening.

PURPOSE: To compare two strategies for colorectal cancer screening: one-time colonoscopy versus fecal immunochemical testing (FIT) (and colonoscopy for positive) every 2 years, in order to determine which strategy provides the highest participation and detection rates in groups of sex and age. METHODS: This analysis was performed with data from the first screening round within the COLONPREV study, a population-based, multicenter, nationwide trial carried out in Spain. Several logistic regression models were applied to identify the influence of the screening test on participation rates and detection of proximal and distal neoplasms, as well to identify the influence of age and sex: women aged 50-59 years, women aged 60-69 years, men aged 50-59 years, and men aged 60-69 years. RESULTS: Participation was higher in women than in men, especially among women aged 50-59 years (25.91 % for colonoscopy and 35.81 % for FIT). Crossover from colonoscopy to FIT was higher among women than men, especially among those aged 60-69 years (30.37 %). In general, detection of any neoplasm and advanced adenoma was higher with colonoscopy than with FIT, but no significant differences were found between the two strategies for colorectal cancer detection. Detection of advanced adenoma in both arms was lower in women [specifically in women aged 50-59 years (OR 0.31; 95 % CI 0.25-0.38) than in men aged 60-69 years]. Women aged 50-59 years in the colonoscopy arm had a higher probability of detection of advanced adenoma (OR 4.49; 95 % CI 3.18-6.35), as well as of detection of neoplasms in proximal and distal locations (proximal OR 19.34; 95 % CI 12.07-31.00; distal OR 11.04; 95 % CI 8.13-15.01) than women of the same age in the FIT arm. These differences were also observed in the remaining groups but to a lesser extent. CONCLUSION: Women were more likely to participate in a FIT-based strategy, especially those aged 50-59 years. The likelihood of detection of any neoplasm was higher in the colonoscopy arm for all the population groups studied, especially in women aged 50-59 years. Distinct population groups should be informed of the benefits of each screening strategy so that they may take informed decisions.

Relationship of colonoscopy-detected serrated polyps with synchronous advanced neoplasia in average-risk individuals.

BACKGROUND: Serrated cancers account for 10% to 20% of all colorectal cancers (CRC) and more than 30% of interval cancers. The presence of proximal serrated polyps and large (≥10 mm) serrated polyps (LSP) has been correlated with colorectal neoplasia. OBJECTIVE: To evaluate the prevalence of serrated polyps and their association with synchronous advanced neoplasia in a cohort of average-risk population and to assess the efficacy of one-time colonoscopy and a biennial fecal immunochemical test for reducing CRC-related mortality. This study focused on the sample of 5059 individuals belonging to the colonoscopy arm. DESIGN: Multicenter, randomized, controlled trial. SETTING: The ColonPrev study, a population-based, multicenter, nationwide, randomized, controlled trial. PATIENTS: A total of 5059 asymptomatic men and women aged 50 to 69 years. INTERVENTION: Colonoscopy. MAIN OUTCOME MEASUREMENTS: Prevalence of serrated polyps and their association with synchronous advanced neoplasia. RESULTS: Advanced neoplasia was detected in 520 individuals (10.3%) (CRC was detected in 27 [0.5%] and advanced adenomas in 493 [9.7%]). Serrated polyps were found in 1054 individuals (20.8%). A total of 329 individuals (6.5%) had proximal serrated polyps, and 90 (1.8%) had LSPs. Proximal serrated polyps or LSPs were associated with male sex (odds ratio [OR] 2.08, 95% confidence interval [CI], 1.76-4.45 and OR 1.65, 95% CI, 1.31-2.07, respectively). Also, LSPs were associated with advanced neoplasia (OR 2.49, 95% CI, 1.47-4.198), regardless of their proximal (OR 4.15, 95% CI, 1.69-10.15) or distal (OR 2.61, 95% CI, 1.48-4.58) locations. When we analyzed subtypes of serrated polyps, proximal hyperplasic polyps were related to advanced neoplasia (OR 1.61, 95% CI, 1.13-2.28), although no correlation with the location of the advanced neoplasia was observed. LIMITATIONS: Pathology criteria for the diagnosis of serrated polyps were not centrally reviewed. The morphology of the hyperplasic polyps (protruded or flat) was not recorded. Finally, because of the characteristics of a population-based study carried out in average-risk patients, the proportion of patients with CRC was relatively small. CONCLUSION: LSPs, but not proximal serrated polyps, are associated with the presence of synchronous advanced neoplasia. Further studies are needed to determine the risk of proximal hyperplastic polyps.

[Present situaltion of living-donor kidney transplantation in Spain and other countries: past, present and future of an excellent therapeutic option]. / Situación actual del trasplante renal de donante vivo en España y otros países: pasado, presente y futuro de una excelente opción terapéutica.

Kidney transplantation from living donor is an established treatment in Spain since the 60s but has maintained a low level of activity until 2000, when the number of procedures and hospitals that perform this therapy experienced a gradual increase, reaching the highest figure in our history in 2009, with 235 living donor kidney transplants (which represents 10% of renal transplant activity). The reasons why living donor kidney transplantation is emerging in our country are diverse and can be focused in four main areas. 1) Better outcomes obtained when using living donors for kidney transplantation than those obtained with kidneys from deceased donors. Younger recipients with better HLA matching, the good health of the donor, the absence of any damages that occur in the kidney secondary to brain death, the small ischemic time and the possibility of preemptive transplantation can explain the best graft and patient survival. 2) The scarcity of sources: the relaxation of entry criteria on the waiting list implies an increasing challenge of the demand for transplant without the contribution of living donor kidney transplantation, especially in young recipients where the chances of obtaining an age-appropriate deceased donor are lower, due to the change in the profile of the deceased donor (increasingly older). 3) Improvement in the safety of the donor: the excellent evaluation and monitoring of donors (based on international standards) plus the use of less invasive surgical techniques are related to a low complication rate and to survival expectancies of living donors being similar to those of the general population. 4) Barriers overcome: The training effort by the transplant teams, hospital and regional coordinations, and the National Transplant Organization is giving excellent results, visible in the gradual increase in the number of hospitals with a program of living donor kidney transplantation and its activity. In addition, desensitization programs and the national cross-over kidney transplantation program have removed barriers to transplantation in cases of ABO incompatibility or positive crossmatch.

Impact of age- and gender-specific cut-off values for the fecal immunochemical test for hemoglobin in colorectal cancer screening.

BACKGROUND: There is no information on the impact of age and gender on the diagnostic yield of different positivity thresholds for the fecal immunochemical test for hemoglobin (FIT). OBJECTIVES: To evaluate the performance of this test at distinct positivity cut-offs in a population-based colorectal cancer (CRC) screening program. METHODS: CRC detection rate (DR), and analysis of resources were evaluated retrospectively, at different cut-offs of FIT (20, 25, 30, 35 and 40µg Hb/g) respect to a reference value (15µg Hb/g), according to age and gender, in a screening population of 10,611 participants of the ColonPrev study (Quintero. NEJM 2013). RESULTS: At the reference cut-off value, 36 CRC and 252 advanced adenomas (AA) were diagnosed. Increasing the cut-off in women ≤60 years decreases colonoscopies performed by 44.5% without modifying the CRC (DR). Same CRC DR was observed in men ≤60 years and women >60 years increasing cut-off at 25-30µg Hb/g. In men >60 years, all increases in the cut-off affected the CRC DR, especially when the cut-off was increased from 35 to 40µg Hb/g (CRC miss rate 25%). CONCLUSIONS: To improve the performance of FIT in CRC screening programs, FIT cut-offs could be individualized by age and gender.

Mineral metabolism disorders, vertebral fractures and aortic calcifications in stable kidney transplant recipients: The role of gender (EMITRAL study).

BACKGROUND AND OBJECTIVES: The relationship between mineral metabolism disorders, bone fractures and vascular calcifications in kidney transplant recipients has not been established. METHOD: We performed a cross-sectional study in 727 stable recipients from 28 Spanish transplant clinics. Mineral metabolism parameters, the semi-quantification of vertebral fractures and abdominal aortic calcifications were determined centrally. RESULTS: Vitamin D deficiency (25OHD3<15ng/ml) was more common in female recipients at CKD-T stages I-III (29.6% vs 44.4%; p=0.003). The inverse and significant correlation between 25OHD3 and PTH was gender-specific and women exhibited a steeper slope than men (p=0.01). Vertebral fractures (VFx) with deformity grade ≥2 were observed in 15% of recipients. Factors related to VFx differed by gender; in males, age (OR 1.04; 95% CI 1.01-1.06) and CsA treatment (OR: 3.2; 95% CI: 1.6-6.3); in females, age (OR 1.07; 95% CI: 1.03-1.12) and PTH levels (OR per 100pg/ml increase: 1.27; 95% CI: 1.043-1.542). Abdominal aortic calcifications were common (67.2%) and related to classical risk factors but not to mineral metabolism parameters. CONCLUSIONS: Vitamin D deficiency is more common among female kidney transplant recipients at earlier CKD-T stages, and it contributes to secondary hyperparathyroidism. Prevalent vertebral fractures are only related to high serum PTH levels in female recipients.

Economic evaluation of colorectal cancer (CRC) screening.

Because of its incidence and mortality colorectal cancer represents a serious public health issue in industrial countries. In order to reduce its social impact a number of screening strategies have been implemented, which allow an early diagnosis and treatment. These basically include faecal tests and studies that directly explore the colon and rectum. No strategy, whether alone or combined, has proven definitively more effective than the rest, but any such strategy is better than no screening at all. Selecting the most efficient strategy for inclusion in a population-wide program is an uncertain choice. Here we review the evidence available on the various economic evaluations, and conclude that no single method has been clearly identified as most cost-effective; further research in this setting is needed once common economic evaluation standards are established in order to alleviate the methodological heterogeneity prevailing in study results.

Risk of advanced proximal neoplasms according to distal colorectal findings: comparison of sigmoidoscopy-based strategies.

BACKGROUND: Screening for colorectal cancer with sigmoidoscopy benefits from the fact that distal findings predict the risk of advanced proximal neoplasms (APNs). This study was aimed at comparing the existing strategies of postsigmoidoscopy referral to colonoscopy in terms of accuracy and resources needed. METHODS: Asymptomatic individuals aged 50-69 years were eligible for a randomized controlled trial designed to compare colonoscopy and fecal immunochemical test. Sigmoidoscopy yield was estimated from results obtained in the colonoscopy arm according to three sets of criteria of colonoscopy referral (from those proposed in the UK Flexible Sigmoidoscopy, Screening for COlon REctum [SCORE], and Norwegian Colorectal Cancer Prevention [NORCCAP] trials). Advanced neoplasm detection rate, sensitivity, specificity, and number of individuals needed to refer for colonoscopy to detect one APN were calculated. Logistic regression analysis was performed to identify distal findings associated with APN. All statistical tests were two-sided. RESULTS: APN was found in 255 of 5059 (5.0%) individuals. Fulfillment of UK (6.2%), SCORE (12.0%), and NORCCAP (17.9%) criteria varied statistically significantly (P < .001). The NORCCAP strategy obtained the highest sensitivity for APN detection (36.9%), and the UK approach reached the highest specificity (94.6%). The number of individuals needed to refer for colonoscopy to detect one APN was 6 (95% confidence interval [CI] = 4 to 7), 8 (95% CI = 6 to 9), and 10 (95% CI = 8 to 12) when the UK, SCORE, and NORCCAP criteria were used, respectively. The logistic regression analysis identified distal adenoma ≥10 mm (odds ratio = 3.77; 95% CI = 2.52 to 5.65) as the strongest independent predictor of APN. CONCLUSIONS: Whereas the NORCCAP criteria achieved the highest sensitivity for APN detection, the UK recommendations benefited from the lowest number of individuals needed to refer for colonoscopy.

Gastrointestinal quality of life improvement of renal transplant recipients converted from mycophenolate mofetil to enteric-coated mycophenolate sodium drugs or agents: mycophenolate mofetil and enteric-coated mycophenolate sodium.

BACKGROUND: In renal transplant (RT) recipients, treatment with enteric-coated mycophenolate sodium (EC-MPS) improves gastrointestinal (GI) tolerability compared with mycophenolate mofetil (MMF). The impact of conversion from MMF to EC-MPS on patient's health-related quality of life (HRQoL) using GI-specific instruments has been scarcely evaluated in randomized trials. METHODS: The present randomized, multicenter, open-labeled, 12-week study included RT recipients experiencing GI adverse events due to MMF treatment. Patients were randomized to continue with MMF (n=54) or change to EC-MPS (n=59). Patients were converted at equimolar doses, and dose was optimized between weeks 2 and 6 to achieve maximum tolerated dose. RESULTS: Incidence of GI complications (particularly diarrhea) was significantly lower in the EC-MPS group (67.8% vs. 87.0%, P=0.015). The baseline-adjusted mean global scores at 12 weeks in GI quality of life index were significantly higher in the EC-MPS group versus MMF (P=0.014). Results at 12 weeks for all secondary scales indicated better HRQoL in the EC-MPS group compared with the MMF group (Gastrointestinal Symptom Rating Scale, Psychological General Well-Being Index, and overall treatment effect). In the EC-MPS group, a higher percentage of patients were receiving intermediate doses of mycophenolic acid (720 mg/day) at 12 weeks compared with MMF (55.4% vs. 27.4%, P=0.003), whereas no differences were observed for high doses (>720 mg/day). CONCLUSIONS: In RT patients with GI undesirable effects due to MMF, switching from MMF to EC-MPS may enable an increase in the maximum tolerated dose of mycophenolic acid and reduce GI complications, thus enhancing patients' GI HRQoL.

Mineral metabolism disorders, vertebral fractures and aortic calcifications in stable kidney transplant recipients: The role of gender (EMITRAL study) / Alteraciones del metabolismo mineral, fracturas vertebrales, y calcificaciones aórticas en receptores estables de trasplante renal: papel del género (estudio EMITRAL)

Antecedentes y objetivos: La relación entre las alteraciones del metabolismo mineral, las fracturas óseas y las calcificaciones vasculares en receptores de un trasplante renal no han sido establecidas. Método: Realizamos un estudio transversal en 727 receptores estables procedentes de 28 centros de trasplante españoles. Se determinaron de manera centralizada los parámetros del metabolismo mineral; también se centralizó la semicuantificación de las fracturas vertebrales y de las calcificaciones de la aorta abdominal. Resultados: La deficiencia de vitamina D (25OHD3 < 15ng/ml) fue más frecuente en mujeres y en los estadios CKD-T I-III (29,6 vs. 44,4%; p=0,003). La relación inversa y significativa observada entre los niveles de 25OHD3 y PTH fue modificada por el género de tal manera que la pendiente fue mayor en las mujeres que en los hombres (p=0,01). Un 15% de los receptores mostró alguna fractura vertebral (VFx) con un grado de deformidad ≥2. Los factores relacionados con la VFx diferían en función del género: en los hombres, la edad (OR: 1,04; IC 95%: 1,01-1,06) y el tratamiento con CsA (OR: 3,2; IC 95: 1,6-6,3); en las mujeres la edad (OR: 1,07; IC 95%: 1,03-1,12) y los niveles de PTH (OR per 100pg/ml increase: 1,27; IC 95%: 1,043-1,542). Las calcificaciones de la aorta abdominal fueron comunes (67,2%) y se relacionaron con los factores de riesgo clásicos, pero no con los parámetros del metabolismo mineral. Conclusiones: La deficiencia de vitamina D es más frecuente en las mujeres receptoras de un trasplante renal y en los estadios más tempranos de la CKD-T, y es un factor que contribuye al desarrollo de hiperparatiroidismo secundario. Las VFx prevalentes están relacionadas con unos niveles más elevados de PTH solamente en las mujeres (AU)

Background and objectives: The relationship between mineral metabolism disorders, bone fractures and vascular calcifications in kidney transplant recipients has not been established. Method: We performed a cross-sectional study in 727 stable recipients from 28 Spanish transplant clinics. Mineral metabolism parameters, the semi-quantification of vertebral fractures and abdominal aortic calcifications were determined centrally. Results: Vitamin D deficiency (25OHD3 < 15 ng/ml) was more common in female recipients at CKD-T stages I–III (29.6% vs 44.4%; p=0.003). The inverse and significant correlation between 25OHD3 and PTH was gender-specific and women exhibited a steeper slope than men (p=0.01). Vertebral fractures (VFx) with deformity grade ≥2 were observed in 15% of recipients. Factors related to VFx differed by gender; in males, age (OR 1.04; 95% CI 1.01-1.06) and CsA treatment (OR: 3.2; 95% CI: 1.6-6.3); in females, age (OR 1.07; 95% CI: 1.03-1.12) and PTH levels (OR per 100 pg/ml increase: 1.27; 95% CI: 1.043-1.542). Abdominal aortic calcifications were common (67.2%) and related to classical risk factors but not to mineral metabolism parameters. Conclusions: Vitamin D deficiency is more common among female kidney transplant recipients at earlier CKD-T stages, and it contributes to secondary hyperparathyroidism. Prevalent vertebral fractures are only related to high serum PTH levels in female recipients (AU)

Objetivos y metodología de las Recomendaciones de la SEN-ONT sobre trasplante renal de donante vivo / Objectives and methodology of SEN-ONT recommendations for living-donor kidney transplantation

No disponible

No disponible

Situación actual del trasplante renal de donante vivo en España y otros países: pasado, presente y futuro de una excelente opción terapéutica / Present situation of living-donor kidney transplantation in Spain and other countries: past, present and future of an excellent therapeutic option

El trasplante renal de donante vivo es un tratamiento establecido en España desde los años sesenta, pero ha mantenido unos escasos niveles de actividad hasta el año 2000, fecha en que comienza un incremento progresivo en el número de procedimientos y de hospitales que realizan esta terapia, alcanzando en el año 2009 la cifra más alta de nuestra historia, con 235 trasplantes renales de donante vivo (que suponen un 10% de la actividad de trasplante renal). Los motivos por los que el trasplante renal de donante vivo está emergiendo en nuestro país son diversos y pueden englobarse en cuatro grandes apartados: 1) M ejores resultados que el trasplante renal de donante fallecido. Receptores más jóvenes con una mejor compatibilidad HLA, el buen estado de salud del donante, la ausencia de los posibles daños que se producen en el riñón secundariamente a la muerte encefálica, el menor tiempo de isquemia y la posibilidad de realizar el trasplante anticipado explican la mejor supervivencia de injerto y de paciente. 2) Necesidad de trasplante de vivo: la flexibilización de criterios de entrada en lista de espera conlleva una mayor dificultad de atender a la demanda de trasplante sin ayuda del trasplante renal de donante vivo, sobre todo en receptores jóvenes en los que las posibilidades de obtener un órgano adecuado a su edad son menores, debido al cambio en el perfil de los donantes fallecidos (cada vez de mayor edad). 3) M ejora en la seguridad del donante: la excelente evaluación y seguimiento de los donantes (basada en estándares internacionales), además de la utilización de técnicas quirúrgicas menos invasivas, conlleva un bajo índice de complicaciones y una esperanza de vida de los donantes similar a la de la población general. 4) Obstáculos superados: el esfuerzo en formación realizado por los equipos de trasplante, coordinaciones hospitalarias, autonómicas y la Organización Nacional de Trasplantes (ONT) está dando excelentes resultados, visibles en el progresivo aumento en el número de hospitales con programa de trasplante renal de donante vivo y en su actividad. Por otra parte, los programas de desensibilización y el programa nacional de donación renal cruzada han eliminado las barreras al trasplante en los casos de incompatibilidad ABO o prueba cruzada positiva (AU)

Kidney transplantation from living donor is an established treatment in Spain since the 60s but has maintained a low level of activity until 2000, when the number of procedures and hospit als t hat perf orm t his t herapy experienced a gradual increase, reaching the highest figure in our history in 2009, with 235 living donor kidney transplants (which represents 10% of renal transplant activity). The reasons why living donor kidney transplantation is emerging in our country are diverse and can be focused in four main areas. 1) Better outcomes obtained when using living donors for kidney transplantation than those obtained with kidneys from deceased donors. Younger recipients with better HLA matching, the good health of the donor, the absence of any damages that occur in the kidney secondary to brain death, the small ischemic time and the possibility of preemptive transplantation can explain the best graft and patient survival. 2) The scarcity of sources: the relaxation of entry criteria on the waiting list implies an increasing challenge of the demand for transplant without the contribution of living donor kidney transplantation, especially in young recipients where the chances of obtaining an age-appropriate deceased donor are lower, due to the change in the profile of the deceased donor (increasingly older). 3) Improvement in the safety of the donor: the excellent evaluation and monitoring of donors (based on international standards) plus the use of less invasive surgical techniques are related to a low complication rate and to survival expectancies of living donors being similar to those of the general population. 4) Barriers overcome: the training effort by the transplant teams, hospital and regional coordinations, and the National Transplant Organization is giving excellent results, visible in the gradual increase in the number of hospitals with a program of living donor kidney transplantation and its activity. In addition, desensitization programs and the national cross-over kidney transplantation program have removed barriers to transplantation in cases of ABO incompatibility or positive crossmatch (AU)

Modelación 3-D para análisis e instrumentación sísmica de la represa La Plata, Puerto Rico

El presente trabajo propone una manera analítica de identificar la localización más adecuada para localizar la instrumentación de Movimiento Fuerte en la represa La Plata en Toa Alta, Puerto Rico. Un modelo tridimensional de elementos finitos fue desarrollado considerando la estructura (represa), el efecto estático y dinámico del agua y el suelo bajo su fundación. Pruebas sencillas para obtener las propiedades dinámicas del concreto y la roca fueron implementadas en el sitio. Tres modelos fueron definidos a través de relaciones de módulos entre el hormigón y la roca de 1, 3.7 y 12.4. Los análisis de los modelos fueron desarrollados en el dominio del tiempo usando un registro artificial de aceleraciones diseñado para la región y diferentes valores de amortiguamiento. Los criterios para localizar la instrumentación fueron: la ubicación de los desplazamientos máximos, la ubicación de las aceleraciones máximas, la captura de los tres primeros modos de vibración de la represa y la aparición del efecto de balanceo (rocking). Dichos puntos estuvieron en general hacia la cresta de la represa en la cercanía del edificio de oficinas. El análisis permitió ubicar la instrumentación de una manera racional y observar la variación de los esfuerzos de tensión en el concreto y aparición de fisuras para las diferentes relaciones de módulos usadas. También se llevo a cabo el trabajo de campo para la instalación de los acelerómetros. (AU)