Food-grade titanium dioxide (E171) and zinc oxide nanoparticles induce mitochondrial permeability and cardiac damage after oral exposure in rats.

Food-grade titanium dioxide (E171) and zinc oxide nanoparticles (ZnO NPs) are found in diverse products for human use. E171 is used as whitening agent in food and cosmetics, and ZnO NPs in food packaging. Their potential multi-organ toxicity has raised concerns on their safety. Since mitochondrial dysfunction is a key aspect of cardio-pathologies, here, we evaluate the effect of chronic exposure to E171 and ZnO NPs in rats on cardiac mitochondria. Changes in cardiac electrophysiology and body weight were measured. E171 reduced body weight more than 10% after 5 weeks. Both E171 and ZnO NPs increased systolic blood pressure (SBP) from 110-120 to 120-140 mmHg after 45 days of treatment. Both NPs altered the mitochondrial permeability transition pore (mPTP), reducing calcium requirement for permeability by 60% and 93% in E171- and ZnO NPs-exposed rats, respectively. Treatments also affected conformational state of adenine nucleotide translocase (ANT). E171 reduced the binding of EMA to Cys 159 in 30% and ZnO NPs in 57%. Mitochondrial aconitase activity was reduced by roughly 50% with both NPs, indicating oxidative stress. Transmission electron microscopy (TEM) revealed changes in mitochondrial morphology including sarcomere discontinuity, edema, and hypertrophy in rats exposed to both NPs. In conclusion, chronic oral exposure to NPs induces functional and morphological damage in cardiac mitochondria, with ZnO NPs being more toxic than E171, possibly due to their dissociation in free Zn2+ ion form. Therefore, chronic intake of these food additives could increase risk of cardiovascular disease.

Trends and sex differences in atrial fibrillation among patients hospitalized due to asthma: Insights from a nationwide population-based discharge database in Spain, 2016-2021.

AIMS: To analyze changes in the prevalence of atrial fibrillation (AF) in patients hospitalized due to asthma; to compare hospital outcomes in asthma patients with and without AF, assessing sex differences; to identify variables associated with the presence of AF; and to analyze the factors associated with in-hospital mortality (IHM) among asthma patients with AF. METHODS: We used data from the Registry of Specialized Care Activity-Basic Minimum Data Set to select all patients aged ≥40 years with an asthma diagnosis in Spain, from 2016 to 2021. We stratified the study population according to the presence of AF and sex. RESULTS: We identified 65,233 hospitalizations that met the inclusion criteria (14.85 % with AF). The prevalence of AF significantly increased over time, with the male sex being a protective factor for its presentation. IHM were significantly higher in patients with AF. Older age, being a woman, congestive heart failure, renal disease, obstructive sleep apnea, hypertension, and hyperthyroidism were associated with the presence of AF. Advanced age and the presence of cancer and COVID-19 were factors associated with a higher IHM, as well as admission to an intensive care unit and the use of invasive mechanical ventilation. There were no association of sex with the IHM. CONCLUSIONS: AF is highly prevalent among subjects hospitalized due to asthma, with this prevalence having increased significantly in Spain over time. The presence of AF in patients with asthma was associated significantly with a higher LOHS and IHM. Sex was not associated with IHM in these patients.

Trends in Anaphylaxis Hospitalizations among Adults in Spain and Their Relationship with Asthma-Analysis of Hospital Discharge data from 2016 to 2021.

(1) Background: Anaphylaxis is a rapid-onset, life-threatening hypersensitivity reaction. This study explores the epidemiological trends and clinical outcomes of adult patients with and without asthma hospitalized for anaphylaxis in Spain from 2016 to 2021. (2) Methods: Data from the Spanish National Hospital Discharge Database (RAE-CMBD) were analyzed. We stratified patients with anaphylaxis based on their asthma diagnosis and evaluated various comorbidities and clinical outcomes. Propensity score matching was used to match confounders. (3) Results: The total number of hospitalizations for anaphylaxis remained stable, with a decrease in 2020 probably due to the COVID-19 pandemic. Drug-induced anaphylaxis increased, in addition to being the main triggering factor. Asthma prevalence among those admitted for anaphylaxis emerged from 7.63% to 10.69%, with a higher frequency of respiratory failure and need for mechanical ventilation in this group; despite this, ICU admissions and in-hospital mortality did not differ significantly between asthmatics and non-asthmatics. Asthma was also not a risk factor for severe anaphylaxis. Multivariable analysis identified advanced age, ischemic heart disease, acute respiratory failure, and invasive mechanical ventilation as factors associated with severe anaphylaxis. (4) Conclusions: This study provides valuable information on the complexity of anaphylaxis, its relationship with asthma, and factors influencing its severity. Overall, clinical outcomes did not differ significantly in asthmatic patients compared to non-asthmatic patients, although asthmatic patients had more respiratory complications. Further research is necessary to delve deeper into the multifactorial nature of anaphylaxis and its implications in clinical practice.

Food-grade titanium dioxide and zinc oxide nanoparticles induce toxicity and cardiac damage after oral exposure in rats.

BACKGROUND: Metallic nanoparticles (NPs) are widely used as food additives for human consumption. NPs reach the bloodstream given their small size, getting in contact with all body organs and cells. NPs have adverse effects on the respiratory and intestinal tract; however, few studies have focused on the toxic consequences of orally ingested metallic NPs on the cardiovascular system. Here, the effects of two food-grade additives on the cardiovascular system were analyzed. METHODS: Titanium dioxide labeled as E171 and zinc oxide (ZnO) NPs were orally administered to Wistar rats using an esophageal cannula at 10 mg/kg bw every other day for 90 days. We evaluated cardiac cell morphology and death, expression of apoptotic and autophagic proteins in cardiac mitochondria, mitochondrial dysfunction, and concentration of metals on cardiac tissue. RESULTS: Heart histology showed important morphological changes such as presence of cellular infiltrates, collagen deposition and mitochondrial alterations in hearts from rats exposed to E171 and ZnO NPs. Intracellular Cyt-C levels dropped, while TUNEL positive cells increased. No significant changes in the expression of inflammatory cytokines were detected. Both NPs altered mitochondrial function indicating cardiac dysfunction, which was associated with an elevated concentration of calcium. ZnO NPs induced expression of caspases 3 and 9 and two autophagic proteins, LC3B and beclin-1, and had the strongest effect compared to E171. CONCLUSIONS: E171 and ZnO NPs induce adverse cardiovascular effects in rats after 90 days of exposure, thus food intake containing these additives, should be taken into consideration, since they translocate into the bloodstream and cause cardiovascular damage.

Trends and Hospital Outcomes in HOSPITAL Admissions for Anaphylaxis in Children with and without Asthma in Spain (2016-2021).

(1) Background: To assess and compare the temporal trends in the incidence, characteristics and hospital outcomes among children with and without asthma who were hospitalized with anaphylaxis in Spain from 2016 to 2021, and identify the variables associated with severe anaphylaxis among children with asthma. (2) Methods: An observational, retrospective study was conducted using a population-based database. The study population included pediatric patients with anaphylaxis. This population was stratified based on whether they had asthma. (3) Results: The number of hospital admissions was stable from 2016 to 2019, dropping in 2020 and raising to the highest number in 2021. A total of 60.63% of hospitalizations occurred in boys and the most common anaphylactic reactions were due to food consumption (67.28%), increasing over time. The in-hospital mortality (IHM) remained stable and under 1% in all the years studied. The incidence of anaphylaxis was 2.14 times higher in children with asthma than in those without asthma (IRR 2.14; 95% CI 1.87-2.44). Furthermore, it was 1.79 times higher in boys with asthma than in those without asthma (IRR 1.79; 95% CI 1.06-2.45) and 2.68 times higher in girls with asthma than in those without asthma (IRR 2.68; 95% CI 2.23-3.12). Asthma was not associated with severe anaphylaxis (OR 1.31; 95% CI 0.88-1.96). (4) Conclusions: The number of hospitalizations for anaphylaxis in children remained stable from 2016 to 2019, dropping in 2020 and recovering in 2021. IHM was low and remained stable during the study period. The incidence of hospitalizations for anaphylaxis was higher in asthmatic children than in non-asthmatics, but there were no differences in the occurrence of severe anaphylaxis among them.

Mapeo de la percepción individual y del entorno organizacional para la práctica clínica basada en la evidencia entre enfermeras renales en España / Mapping of individual perception and the organizational environment for evidence-based clinical practice among renal nurses in Spain

Objetivo: Analizar la percepción de las enfermeras renales en España en relación con el entorno organizacional para la práctica clínica basada en la evidencia (PCBE); y determinar qué factores profesionales y del contexto influyen en esta percepción. Material y Método: Estudio observacional transversal multicéntrico, en 15 servicios de nefrología de distintos hospitales en España y 2 centros de diálisis. Se utilizaron los instrumentos Practice Environment Scale of Nursing Work Index (PES-NWI) y Evidence Based Practice Questionnarie (EBPQ). Se realizó un análisis estadístico descriptivo, bivariado (ANOVA, Kruskall-Wallis), y regresión logística con la puntuación total del EBPQ como variable dependiente.Resultados: Se recibieron 397 encuestas (participación 84,28%), tras depuración encuestas, fueron válidas 382 (81,1% población): 82,7% mujeres, edad media 42 años, media de experiencia profesional como enfermera 18,2 años (12,2 años en nefrología), 94,8% clínicas, 81,9% de hemodiálisis. Puntuación media PES-NWI 62,35±15,10 (IC 95%: 60,78-48,06). Presentaron menores puntuaciones en algunos factores del PES-NWI las enfermeras de centros >500 enfermeras, que trabajan en hemodiálisis y >11 años de experien-cia profesional. Las enfermeras gestoras presentaron mayores puntuaciones en todos los factores del PES-NWI. Puntuación media EBPQ 81,05±21,92 (IC 95%: 78,70-83,4). Presentaron mayores puntuaciones en varios factores del EBPQ las enfermeras con menor experiencia profesional, mejor puntuación en PES-NWI y que poseían estudios de postgrado.Conclusiones: Los factores que más influyen en la percepción de las enfermeras renales en España son la experiencia profesional, el rol dentro de la organización, un contexto favorable y la formación de postgrado.(AU)

Objective: To analyze the perception of renal nurses in Spain regarding the organizational environment for evidence-based clinical practice (EBCP), and to determine what professional and context factors influence such perception.Material and Method: A crosssectional observational multicenter study was carried out in 15 nephrology services from different Spanish hospitals and 2 dialysis centers. The Practice Environment Scale of Nursing Work Index (PES-NWI) and Evidence-Based Practice Questionnaire (EBPQ) tools were used. A descriptive, bivariate statistical analysis (ANOVA, Kruskall-Wallis) and logistic regression were performed with the EBPQ total score as the dependent variable.Results: A total of 397 surveys were received (participation rate: 84.28%), and after processing the surveys 382 were valid (81.1% of the population): 82.7% were women, with a mean age of 42 years, a mean of 18.2 years of professional experience as a nurse (12.2 years in nephrology), 94.8% were clinical nurses, and 81.9% worked in hemodialysis. The average PES-NWI score was 62.35±15.10 (95% CI:60.78-48.06). Nurses in centers with more than 500 nurses, those who worked in hemodialysis, and those with more than 11 years of professional experience had lower scores on some PES-NWI factors. Nurse managers had higher scores in all PES-NWI factors. The average EBPQ score was 81.05±21.92 (95% CI:78.70-83.4). Nurses with less professional experience the better PES-NWI scores; also, postgraduate nurses had higher scores on several EBPQ factors. Conclusions: Factors that most influence the perception of Spanish renal nurses are professional experience, role within the organization, a favorable context, and postgraduate education.(AU)

Trends in asthma hospitalizations among adults in Spain: Analysis of hospital discharge data from 2011 to 2020.

AIMS: To analyze trends in asthma hospitalizations in patients over 15 years of age in Spain. To identify possible changes in incidence, demographic characteristics, clinical conditions, and outcomes. METHODS: We conducted an observational retrospective epidemiological study using the Spanish National Hospital Discharge Database and included all patients hospitalized with a diagnosis of asthma from 2011 to 2020. RESULTS: A total of 1,102,923 patients were hospitalized with a code for asthma in any diagnostic position; of these, 153,749 (13.94%) had asthma coded as the primary diagnosis (asthma exacerbation). The number of patients with an asthma exacerbation decreased over time, from 15,356 in 2011 to 8804 in 2020. In-hospital mortality (IHM) remained low (around 1.5%) and stable in this subgroup of patients. When the diagnosis of asthma appeared in any diagnostic position, hospitalizations increased for all ages and sexes. In this case, a significant change was observed for IHM, which increased from 3.27% in 2011-12 to 4.36% in 2019-20 (p < 0.001). The main risk factors for IHM in both cases were age over 65 years, need for mechanical ventilation, and associated diagnoses of pneumonia, heart disease, or atrial fibrillation. In contrast, obesity was a predictor of lower mortality. CONCLUSION: Our results suggest a decline in the incidence of hospitalizations for asthma exacerbations from 2011 to 2020. In contrast, the number of patients with asthma in any diagnostic position increased progressively, as did mortality, probably owing to an increase in comorbidities in a gradually ageing population.

Influencia de la orientación de la luz arterial del catéter venoso central tunelizado para hemodiálisis en la disfunción precoz / Influence of arterial lumen orientation of the tunnelled central venous catheter for haemodialysis on early dysfunction

Objetivo: El objetivo del estudio fue analizar si la orientación lateral o medial de la luz arterial de los catéteres influye en su disfunción precoz.Material y Método: Estudio observacional prospectivo de 24 meses de duración. Se incluyeron pacientes adultos en hemodiálisis a los que se les canaliza por vez primera un catéter venoso tunelizado modelo Palindrome® o Bioflo Duramax®. Variables: orientación de luz arterial, modelo de catéter, socio-demográficas-clínicas, flujos de bomba de sangre, presiones arteriales y venosas, conductancia, complicaciones y características definitorias de disfunción precoz.Resultados: Se estudiaron 178 pacientes, con una edad media 64,4±15,1 años; 108 hombres; 105 con luz arterial en orientación lateral y 73 con orientación medial. Hubo disfunción precoz en 30 casos (16,9%): orientación lateral 63,3% (n=19) vs orientación medial 36,7% (n=11), (p=0,621). En todos los casos con disfunción precoz, fue necesario invertir las luces de los catéteres a las conexiones del circuito extracorpóreo, por un flujo de bomba<250 ml/min, siendo más frecuente en los catéteres Palindrome® con luz arterial en orientación lateral, 87,5% (n=7) vs orientación medial 12,5% (n=1), (p=0,063).Conclusiones: En nuestra muestra, la orientación de la luz arterial no influyó en la disfunción precoz de los catéteres. (AU)

Introduction: Dysfunction and infections are the most frequent causes of removal of tunneled central venous hemodialysis catheters. Objective: To analyse whether the lateral or medial orientation of the catheter’s arterial line influences early dysfunction. Material and Method: Prospective observational study of 24 months’ duration. Adult hemodialysis patients undergoing first-time cannulation of a tunneled venous catheter of the Palindrome® or Bioflo Duramax® model were included. Variables: arterial line orientation, catheter model, socio-demographic and clinical characteristics, blood pump flows, arterial and venous pressures, conductance, complications and defining characteristics of early dysfunction. Results: A total of 178 patients were studied, mean age 64.4±15.1 years; 108 men; 105 with arterial line in lateral orientation and 73 with medial orientation. There was early dysfunction in 30 cases (16.9%): lateral orientation 63.3% (n=19) vs medial orientation 36.7% (n=11), (p=0.621). In all cases with early dysfunction, it was necessary to reverse the catheter line to the extracorporeal circuit connections, due to a pump flow <250 ml/min, being more frequent in Palindrome® catheters with arterial line in lateral orientation, 87.5% (n=7) vs medial orientation 12.5% (n=1), (p=0.063). (AU)

Recent Advances in Designing Fibrous Biomaterials for the Domain of Biomedical, Clinical, and Environmental Applications.

Unique properties and potential applications of nanofibers have emerged as innovative approaches and opportunities in the biomedical, healthcare, environmental, and biosensor fields. Electrospinning and centrifugal spinning strategies have gained considerable attention among all kinds of strategies to produce nanofibers. These techniques produce nanofibers with high porosity and surface area, adequate pore architecture, and diverse chemical compositions. The extraordinary characteristics of nanofibers have unveiled new gates in nanomedicine to establish innovative fiber-based formulations for biomedical use, healthcare, and a wide range of other applications. The present review aims to provide a comprehensive overview of nanofibers and their broad range of applications, including drug delivery, biomedical scaffolds, tissue/bone-tissue engineering, dental applications, and environmental remediation in a single place. The review begins with a brief introduction followed by potential applications of nanofibers. Finally, the future perspectives and current challenges of nanofibers are demonstrated. This review will help researchers to engineer more efficient multifunctional nanofibers with improved characteristics for their effective use in broad areas. We strongly believe this review is a reader's delight and will help in dealing with the fundamental principles and applications of nanofiber-based scaffolds. This review will assist students and a broad range of scientific communities to understand the significance of nanofibers in several domains of nanotechnology, nanomedicine, biotechnology, and environmental remediation, which will set a benchmark for further research.

Rectal cancer at the peritoneal reflection. Preoperative MRI accuracy and histophatologic correlation. Prospective study.

INTRODUCTION: To investigate magnetic resonance imaging (MRI) accuracy for determining the location of rectal tumors with respect to the peritoneal reflection (PR) and its potential involvement. METHODS: Prospective study of 161 patients ongoing surgery for rectal cancer. A double-ink method has been aplied to examine surgical specimen, orange ink for the serosal surface and indian ink for the mesorrectal margin, and assess preoperative MRI accuracy. RESULTS: Twenty-two tumors were located above, 65 at and 74 below PR. MRI accuracy was 90.6% for determining tumor's location with respect to the PR and 80.5% for defining peritoneal involvement. For classifying tumors according to their intra or extraperitoneal location an accuracy of 92.5% was set for MRI. Histophatologic peritoneal involvement was found in 28.7% of tumors located above or at the PR. CONCLUSIONS: Magnetic resonance imaging accurately predicts the location of rectal tumors with respect to the PR and its potential involvement. The double-ink method is useful to assess serosal involvement (pT4a) and to distinguish mesorrectal fascia from the peritonealized surface.

Systemic epigallocatechin gallate protects against retinal degeneration and hepatic oxidative stress in the P23H-1 rat.

Retinitis pigmentosa (RP) is a group of inherited retinal disorders that lead to photoreceptor loss. RP has been reported to be related to oxidative stress, autophagy, and inflammation. (-)-Epigallocatechin gallate (EGCG), the most abundant catechin-based flavonoid in green tea leaves, has significant antioxidant, anti-carcinogenic, antimicrobial, and neuroprotective properties. EGCG, given its low molecular weight and hydrophilic properties, can cross the blood-retinal barrier and is able to reach different ocular tissues such as the lens, cornea, and retina. EGCG has been shown to provide retinal protection against ischemia; sodium nitroprusside-, N-methyl-D-aspartate-, lipopolysaccharide-, light-, sodium iodate-, or H2O2-induced damage and diabetic retinopathy. This suggests that systemic EGCG administration has the potential to protect against retinal degenerative or neurodegenerative diseases such as RP. The aim of this work was to investigate whether EGCG can protect against RP progression in the animal P23H line 1, the model of RP. Albino P23H rats were crossed with pigmented Long Evans rats to produce offspring exhibiting the clinical features of RP. Pigmented P23H rats were treated via intraperitoneal injection with saline or EGCG at a dose of 25 mg/kg every week from P100 to P160 and then compared to wild-type Long Evans rats. Rats treated with EGCG showed better visual and retinal electrical function with increased contrast sensitivity and b-wave values compared with those observed in P23H rats treated with vehicle. EGCG reduced lipid peroxidation and increased total antioxidant capacity and catalase and superoxide dismutase activities. No differences were observed in visual acuity, nitrate levels, nitrite levels or glutathione S-transferase activity. In conclusion, EGCG not only reduced the loss of visual function in P23H rats but also improved the levels of antioxidant enzymes and reduced oxidative damage. This study was approved by the Institutional Animal Care and Use Committee (CEICA) from the University of Zaragoza under project license PI12/14 on July 11, 2014.

Effects of Daily Melatonin Supplementation on Visual Loss, Circadian Rhythms, and Hepatic Oxidative Damage in a Rodent Model of Retinitis Pigmentosa.

Retinitis pigmentosa (RP) is a group of inherited neurodegenerative diseases characterized by a progressive loss of visual function that primarily affect photoreceptors, resulting in the complete disorganization and remodeling of the retina. Progression of the disease is enhanced by increased oxidative stress in the retina, aqueous humor, plasma, and liver of RP animal models and patients. Melatonin has beneficial effects against age-related macular degeneration, glaucoma, and diabetic retinopathy, in which oxidative stress plays a key role. In the present study, we used the P23HxLE rat as an animal model of RP. Melatonin treatment (10 mg/kg b.w. daily in drinking water for 6 months) improved the parameters of visual function and decreased the rate of desynchronization of the circadian rhythm, both in P23HxLE and wild-type rats. Melatonin reduced oxidative stress and increased antioxidant defenses in P23HxLE animals. In wild-type animals, melatonin did not modify any of the oxidative stress markers analyzed and reduced the levels of total antioxidant defenses. Treatment with melatonin improved visual function, circadian synchronization, and hepatic oxidative stress in P23HxLE rats, an RP model, and had beneficial effects against age-related visual damage in wild-type rats.

Ultrasound-based criteria for adequate peripheral venous access in therapeutic apheresis procedures.

BACKGROUND: Apheresis procedures require adequate vascular access to achieve adequate inlet flow rates. Central dialysis-type catheters are often used in apheresis, despite their multiple risks. Peripheral venous access is a safe and effective option for many patients. AIM: We previously demonstrated that ultrasound guidance reduces central venous catheter use in apheresis patients; however, no validated criteria for preprocedural evaluation of peripheral veins exist. Here, we hypothesized that ultrasound-based criteria could predict the adequacy of a peripheral vein for apheresis procedures. PATIENTS/METHODS: In this pilot cohort study, we reviewed the procedural outcomes for 50 cases of peripheral venous procedures that used our ultrasound-based criteria. RESULTS: Of the procedures that met our criteria, 96% (46/48) were successfully completed. Overall, our criteria had 100% sensitivity, 50% specificity, 96% positive predictive value, and 100% negative predictive value. CONCLUSION: Our criteria justify an evidence-based ultrasound-guided standard for evaluation of peripheral venous access for apheresis procedures.

Speeding in the city of Xalapa, Mexico: Prevalence and associated factors.

OBJECTIVE: To estimate the prevalence of speeding in the city of Xalapa, Veracruz, in Mexico and to identify factors potentially associated to this risk behavior. METHODS: A cross-sectional study was conducted on December 2019 in Xalapa, Veracruz. Speed measurement was conducted in a random sample of 10% of all the main roads in the urban area (n = 12). Observations were conducted over the course of one week at different times spending no more than 1.5 h in each site at a time. All vehicles circulating in each observation site during the data collection were included in the sample. Characteristics of drivers, vehicles and the environment were also collected and analyzed, using logistic regression analysis and a multiple ordinal regression model to identify factors associated to speeding and more serious violations of speed limits. RESULTS: Average speed of the 3,390 vehicles observed was 50.97 km/h. Prevalence of speeding was 65.66% (95%-CI: 64.04-67.26%); 26.96% (95%-CI: 25.47-28.49) exceeded the speed limit by 50%. Speeding and more serious violations of speed limits were more frequent in light vehicles, residential zones and during weekends. More serious violations of speed limits were also more frequent on smaller roads, where speed limit were lower and during morning hours. CONCLUSIONS: The great majority of vehicles transgress speed limits in Xalapa, Veracruz. Our results support the urgent need to implement speed control measures in the city. Changes in road infrastructure design, as well as promoting a comprehensive speeding legislation (with adequate speed limits and correctly enforced) aimed at reducing exposure to this key risk factor are recommended. As evaluation of road safety interventions is key, our data could be used as a baseline to evaluate the effects and impact of future interventions implemented in this Mexican city.

Rectal cancer at the peritoneal reflection. Preoperative MRI accuracy and histophatologic correlation. Prospective study. / Cáncer de recto a nivel de la reflexión peritoneal. Exactitud de la RM preoperatoria y correlación anatomopatológica. Estudio prospectivo.

INTRODUCTION: To investigate magnetic resonance imaging (MRI) accuracy for determining the location of rectal tumors with respect to the peritoneal reflection (PR) and its potential involvement. METHODS: Prospective study of 161 patients ongoing surgery for rectal cancer. A double-ink method has been aplied to examine surgical specimen, orange ink for the serosal surface and indian ink for the mesorrectal margin, and assess preoperative MRI accuracy. RESULTS: Twenty-two tumors were located above, 65 at and 74 below PR. MRI accuracy was 90.6% for determining tumor's location with respect to the PR and 80.5% for defining peritoneal involvement. For classifying tumors according to their intra or extraperitoneal location an accuracy of 92.5% was set for MRI. Histophatologic peritoneal involvement was found in 28.7% of tumors located above or at the PR. CONCLUSIONS: Magnetic resonance imaging accurately predicts the location of rectal tumors with respect to the PR and its potential involvement. The double-ink method is useful to assess serosal involvement (pT4a) and to distinguish mesorrectal fascia from the peritonealized surface.