Computed Tomography With Intravenous Contrast Alone: The Role of Intra‐abdominal Fat on the Ability to Visualize the Normal Appendix in Children

Background Computed tomography ( CT ) with enteric contrast is frequently used to evaluate children with suspected appendicitis. The use of CT with intravenous ( IV ) contrast alone ( CT IV ) may be sufficient, however, particularly in patients with adequate intra‐abdominal fat ( IAF ). Objectives The authors aimed 1) to determine the ability of radiologists to visualize the normal (nondiseased) appendix with CT IV in children and to assess whether IAF adequacy affects this ability and 2) to assess the association between IAF adequacy and patient characteristics. Methods This was a retrospective 16‐center study using a preexisting database of abdominal CT scans. Children 3 to 18 years who had CT IV scan and measured weights and for whom appendectomy history was known from medical record review were included. The sample was chosen based on age to yield a sample with and without adequate IAF . Radiologists at each center reread their site's CT IV scans to assess appendix visualization and IAF adequacy. IAF was categorized as “adequate” if there was any amount of fat completely surrounding the cecum and “inadequate” if otherwise. Results A total of 280 patients were included, with mean age of 10.6 years (range = 3.1 to 17.9 years). All 280 had no history of prior appendectomy; therefore, each patient had a presumed normal appendix. A total of 102 patients (36.4%) had adequate IAF . The proportion of normal appendices visualized with CT IV was 72.9% (95% confidence interval [ CI ] = 67.2% to 78.0%); the proportions were 89% (95% CI  = 81.5% to 94.5%) and 63% (95% CI  = 56.0% to 70.6%) in those with and without adequate IAF (95% CI for difference of proportions = 16% to 36%). Greater weight and older age were strongly associated with IAF adequacy (p < 0.001), with weight appearing to be a stronger predictor, particularly in females. Although statistically associated, there was noted overlap in the weights and ages of those with and without adequate IAF . Conclusions Protocols using CT with IV contrast alone to visualize the appendix can reasonably include weight, age, or both as considerations for determining when this approach is appropriate. However, although IAF will more frequently be adequate in older, heavier patients, highly accurate prediction of IAF adequacy appears challenging solely based on age and weight. Resumen Tomografía Computarizada Únicamente con Contraste Intravenoso: El Papel de la Grasa Intrabadominal en la Capacidad para Visualizar el Apéndice Normal en los Niños Introduction La tomografía computarizada ( TC ) con contraste entérico es usada frecuentemente para evaluar a los niños con sospecha de apendicitis. El uso de la TC únicamente con contraste intravenoso ( TC IV ) puede ser suficiente, especialmente en pacientes con adecuada grasa intrabdominal ( GIA ). Objetivos 1) Determinar la capacidad de los radiólogos para visualizar el apéndice normal (sin enfermedad) con TC IV en niños, y valorar si la cantidad de GIA afecta a esta capacidad; y 2) valorar la asociación entre la idoneidad de la GIA y las características del paciente. Metodología Estudio retrospectivo de 16 hospitales que utilizó una base de datos prexistente de TC abdominales. Se incluyó a los niños entre 3 y 18 años que tenían una TC IV , una medida del peso e historia de apendectomía conocida por la revisión de la historia clínica. La muestra se eligió en base a la edad con el fin de conseguir una muestra con y sin GIA adecuada. Los radiólogos de cada centro releyeron las TC IV de sus centros para valorar la visualización del apéndice y la adecuación de la GIA . La GIA se clasificó como “adecuada” si había cualquier cantidad de grasa completamente alrededor del ciego e “inadecuada” si era de otra manera. Resultados Se incluyeron 280 pacientes, con una media de edad de 10,6 años (rango 3,1 a 17,9 años). Ninguno tenía historia previa de apendectomía; por lo tanto todos los pacientes tuvieron un apéndice presumiblemente normal. Ciento dos pacientes (36,4%) tuvieron GIA adecuada. El porcentaje de apéndices normales visualizados con TC IV fue de 72,9% ( IC 95% = 67,2% a 78,0%); la proporción fue 89% ( IC 95% = 81,5% a 94,5%), y 63% ( IC 95% = 56,0% a 70,6%) en aquéllos con y sin GIA adecuada ( IC 95% para la diferencia de proporciones = 16% a 36%). El mayor peso y la mayor edad se asociaron fuertemente con la adecuación de la GIA (p < 0,001), y el peso resultó ser el mayor factor predictivo, especialmente en mujeres. Aunque se asoció estadísticamente, se vio un solapamiento en los pesos y edades de aquéllos con y sin GIA adecuada. Conclusiones Los protocolos que usan la TC IV para visualizar el apéndice pueden razonablemente incluir el peso, la edad, o ambas como consideraciones para determinar cuándo esta aproximación es apropiada. Sin embargo, aunque la cantidad de GIA será frecuentemente más apropiada en los pacientes más mayores y de mayor peso, la predicción certera de adecuación de GIA es altamente desafiante si se basa sólo en la edad y el peso.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99695/1/acem12185.pd

Feasibility study of computed tomography colonography using limited bowel preparation at normal and low-dose levels study

The purpose was to evaluate low-dose CT colonography without cathartic cleansing in terms of image quality, polyp visualization and patient acceptance. Sixty-one patients scheduled for colonoscopy started a low-fiber diet, lactulose and amidotrizoic-acid for fecal tagging 2 days prior to the CT scan (standard dose, 5.8–8.2 mSv). The original raw data of 51 patients were modified and reconstructed at simulated 2.3 and 0.7 mSv levels. Two observers evaluated the standard dose scan regarding image quality and polyps. A third evaluated the presence of polyps at all three mSv levels in a blinded prospective way. All observers were blinded to the reference standard: colonoscopy. At three times patients were given questionnaires relating to their experiences and preference. Image quality was sufficient in all patients, but significantly lower in the cecum, sigmoid and rectum. The two observers correctly identified respectively 10/15 (67%) and 9/15 (60%) polyps ≥10 mm, with 5 and 8 false-positive lesions (standard dose scan). Dose reduction down to 0.7 mSv was not associated with significant changes in diagnostic value (polyps ≥10 mm). Eighty percent of patients preferred CT colonography and 13% preferred colonoscopy (P<0.001). CT colonography without cleansing is preferred to colonoscopy and shows sufficient image quality and moderate sensitivity, without impaired diagnostic value at dose-levels as low as 0.7 mSv

Design of agile supply chains including analysing the trade-off between number of partners and reliability

The reliability of supply partners is particularly vital in agile supply chains as it is vulnerable to the inability of a supply partner to meet its high responsiveness and flexibility requirements resulting in the disruption of the whole network. Disruption can have expensive and extensive results for the entire agile supply chain. To mitigate the risk of disruption and improve the reliability of the whole agile supply chain, decision-makers need to pay more attention to supply chain design and construction, whilst simultaneously taking into account the sourcing strategy decisions. This paper proposes a series of models for the design of agile supply chains using dynamic programming modelling. These provide decision-makers with a systematic way of analysing one of the key decisions of sourcing strategy, namely the trade-off between the number of supply partners and reliability. The efficacy of the models is demonstrated through their application to a Chinese bus and coach manufacturer by way of an empirical illustration. The results show that this approach is effective for this application and it can be applied in other related decision-making scenarios. The methods offered in this paper provide managers with a practical tool to design their agile supply chains while considering the trade-offs between the number of partners and the reliability of the entire agile supply chain

Strategic inventories under limited commitment

In a dynamic storable good market where demand changes over time, we investigate the producer's strategic incentives to hold inventories in response to the possibility of buyer stockpiling. The literature on storable goods has demonstrated that buyer stockpiling in anticipation of higher future prices harms the producer's profitability, particularly when the producer cannot commit to future prices. We show that the producer's inventories act as a strategic device to mitigate the loss from the lack of commitment. Our results provide a rationale for the producer's inventory behavior that sheds new light on the well-documented empirical evidence about inventories