The most common cause of acute right lower quadrant (RLQ) pain requiring surgery is acute appendicitis (AA). This narrative's focus is on imaging procedures in the diagnosis of AA, with consideration of other diseases causing RLQ pain. In general, Computed Tomography (CT) is the most accurate imaging study for evaluating suspected AA and alternative etiologies of RLQ pain. Data favor intravenous contrast use for CT, but the need for enteric contrast when intravenous contrast is used is not strongly favored. Radiation exposure concerns from CT have led to increased investigation in minimizing CT radiation dose while maintaining diagnostic accuracy and in using algorithms with ultrasound as a first imaging examination followed by CT in inconclusive cases. In children, ultrasound is the preferred initial examination, as it is nearly as accurate as CT for the diagnosis of AA in this population and without ionizing radiation exposure. In pregnant women, ultrasound is preferred initially with MRI as a second imaging examination in inconclusive cases, which is the majority.The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every three years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.
Monochorionic monozygotic twins frequently suffer complications from the presence of vascular anastomoses in their monochorionic placentas. Also, sharing of perfusion zones may be unequal, leading to marked growth discordance. This paper analyzes four measures of perinatal outcome (gestational age at delivery, perinatal mortality, birth weight discordance, and presence/absence of hydramnios) according to the vascular patterns of the monochorionic placentas. The worst clinical outcomes were associated with arteriovenous anastomoses in the absence of arterio‐arterial and veno‐venous anastomoses. The vascular patterns of monochorionic placentas cause significant fetal environmental differences within pairs of monochorionic monozygotic twins. These differences may cause life‐long discordance for several phenotypic traits that are not genetically based, and which cause monochorionic monozygotic twins to be “non‐identical.” © 1996 Wiley‐Liss, Inc.
Abstract-During the 1990s, computed tomography (CT) and magnetic resonance (MR) imaging underwent extensive technological advancement and expanded clinical use in patients with venous thromboembolic disease, particularly with regard to evaluation of the pulmonary vasculature. In many institutions, helical (spiral) CT pulmonary angiography has become the initial imaging study of choice to evaluate patients with suspected pulmonary embolism, supplanting ventilation/perfusion scintigraphy. In addition, CT venography of the pelvis and lower extremities is often incorporated into the CT angiography protocol to identify or exclude concurrent deep venous thrombosis. MR pulmonary angiography and MR venography are second-line diagnostic tools because of their higher cost, limited availability, and other logistical constraints. As the technology improves and becomes more widely available, MR imaging may play a greater role in the evaluation of patients with venous thromboembolic disease. Key Words: thrombosis Ⅲ pulmonary heart disease Ⅲ imaging Ⅲ MRI D uring the 1990s, technological advances in computed tomography (CT) and magnetic resonance (MR) imaging made these techniques applicable to the diagnosis of venous thromboembolic disease, particularly for the pulmonary vasculature in patients with suspected pulmonary embolism (PE). At the opening of the third millennium, in many institutions, helical (spiral) CT pulmonary angiography (CTPA) has become the initial imaging study of choice for evaluating patients with suspected PE, supplanting ventilation/perfusion (V/Q) scintigraphy by reducing indeterminate examinations. 1-4 CT venography (CTV) of the pelvic and lower extremity veins after CTPA of the pulmonary arteries has been advocated by some as an adjunct to helical CT for detection of concurrent deep venous thrombosis (DVT) using a single imaging technique for detection of venous thromboembolic disease.Although MR imaging produces high tissue contrast without ionizing radiation, currently, this technique is less popular than CT for evaluation of acute venous thromboembolism (VTE) because of technical limitations, higher costs, limited availability, and other logistical considerations. As technology improves, however, MR pulmonary angiography (MRPA) and MR venography (MRV) may play a greater role in the evaluation of patients with venous thromboembolic disease.This article reviews applications of CT and MR imaging in the clinical evaluation of patients with suspected venous thromboembolic disease. CT Pulmonary AngiographyCTPA has gained acceptance as a first-line imaging study in cases of suspected acute PE, replacing traditional V/Q scintigraphy at many institutions. In general, V/Q scanning is reserved for patients in whom motion artifact or poor right heart function limit the quality of CT examination and those with contraindications to intravenous radiographic contrast.After contrast administration, CTPA provides visualization of the pulmonary arterial system in the axial plane, and multiplanar and three-dimensional...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.