Hollow Viscus Perforation

Etiology The presence of extraluminal air in an acutely ill patient with abdominal pain is an ominous sign that usually indicates perforation of a hollow viscus. Common causes include gastroduodenal peptic ulcer disease, perforation of a gastrointestinal neoplasm, acute appendicitis with perforation, and acute colonic or (less often) small bowel diverticulitis, including Meckel's diverticulitis. Other considerations include iatrogenic perforations caused by catheters or endoscopes, perforations caused…

Acute Appendicitis

Etiology Acute appendicitis results from obstruction of the appendiceal lumen from any cause (most commonly a fecalith), leading to overdistention and superinfection and, if not treated promptly, to perforation and peritonitis. Epidemiology Acute appendicitis is a common clinical concern in patients presenting to the emergency department with abdominal pain, with a lifetime risk of 5% to 7%. The mortality rate is less than 1% but may…

Ureteral and Kidney Stones

Etiology Renal calculi are typically caused by crystallization of supersaturated stone-forming materials in the urine. Calcium, in the form of calcium oxalate, calcium phosphate, and calcium urate, is the most common stone-forming material. Uric acid is the second most common component. Other less common components include xanthine, cystine, struvite, and precipitation of medications such as the protease inhibitor indinavir sulfate in persons infected with human immunodeficiency…

Positron Emission Tomography and Positron Emission Tomography/Computed Tomography Clinical Applications

The focus of this chapter is on positron emission tomography (PET) and PET and computed tomography (PET/CT) applications specific to the tumors arising in the gastrointestinal tract and female gynecologic organs, excluding systemic malignancies such as lymphoma and melanoma, which can manifest in the abdomen ( Figure 13-1 ), as well as other approved extraabdominal malignancies that can metastasize to the abdomen, such as lung and…

Positron Emission Tomography and Computed Tomography Technique and Instrumentation

Technical Aspects Positron emission tomography and computed tomography (PET/CT) represents the successful technical combination of multidetector computed tomography (MDCT) and PET into a single scanner. PET with the fluorine-18 (18F)–labeled glucose analog fluorodeoxyglucose (FDG) provides metabolic imaging of tissues, both normal and diseased. FDG-PET provides valuable qualitative and quantitative metabolic information for both diagnosis and management. PET has been shown to be of value in diagnosing…

Advanced Magnetic Resonance Imaging Applications

Technical Aspects Magnetic resonance imaging (MRI) has evolved significantly since its infancy, with major advances in hardware, software, coil developments, sequence development, and contrast agents. Industry and academia continue to advance the field with continued exciting emerging technologies. The discussion in this chapter focuses on the recent emergence of parallel imaging, 3.0-Tesla (T) clinical scanners with high field strength, dedicated contrast agents, perfusion and dynamic contrast-enhanced…

Contrast Media and Contrast-Enhanced Magnetic Resonance Imaging

Technical Aspects Contrast agents enhance the visualization of vascular structures as well as pathologic tissues, which appear more prominent against the background of normal tissue. Development of novel contrast agents continues to be an exciting area, with new targeted agents, blood pool agents, and agents based on nanoparticle technologies. This discussion is focused on water-soluble gadolinium chelates used in abdominal and pelvic magnetic resonance imaging (MRI).…

Principles of Magnetic Resonance Imaging Physics

Technical Aspects The principles of magnetization and physics allow us to create images via magnetic resonance imaging (MRI) noninvasively. In this chapter, an overview is provided on how images are created, illustrating the concepts of protons, radiofrequency (RF) excitation, T1 and T2 relaxation, image acquisition, spatial encoding, and Fourier transform analysis and k-space. Magnetization and Protons The nucleus of choice for imaging is hydrogen because the…

Computed Tomography Contrast Media and Principles of Contrast Enhancement

All radiologic contrast media available for intravascular use depend on iodine for their radiopacity. Ideally, contrast media should be inert in every respect. But unlike other therapeutic medications, contrast media are used in larger quantities and participate in numerous physiologic and pharmacokinetic interactions after intravenous administration. Their interactions not only affect tissue characteristics but also may have significant effects on patient health. Contrast Enhancement Principles The…

Recent Advances

For almost 4 decades, computed tomography (CT) has made a remarkable impact on clinical practice. The rapid advances in both CT technology and software have widened the clinical utility of CT of the abdomen and pelvis. The benefits of multidetector CT (MDCT) over single-detector CT include increased temporal and spatial resolution, decreased image noise, and increased anatomic coverage. Better z-axis resolution and larger scan volumes result…

Principles of Computed Tomography Physics, Instrumentation, and Radiation Safety

Computed Tomography Physics In the past decade, computed tomography (CT) has undergone tremendous technical advances. In 1992, the first dual-slice CT scanner (CT Twin, formerly Elscint Technologies, Haifa, Israel) was introduced. In 1998, the quad-slice CT scanners were introduced. In 2002, the 16-slice CT scanner became available. With these scanners it became possible to perform coronary CT angiography, multiphasic examinations, and virtual endoscopy studies. In 2004,…

Advanced Ultrasound Techniques: Liver Elastography, Contrast-Enhanced Ultrasonography, and Four-Dimensional Ultrasound

Elastography Principle Physicians have long used the technique of palpation in the clinical setting. The underlying principle of palpation lies in the ability to feel stiffer tissue in the background of softer tissue when pressed (palpated). Ultrasound brings this concept to the imaging platform wherein the deformation caused by a force can be imaged, and that deformation can be quantified either visually or quantitatively. Pathologic tissue…

Tissue Harmonic Imaging and Doppler Ultrasound Imaging

Tissue Harmonic Imaging Technical Aspects Fundamental frequency is the original frequency of the acoustic beam emitted from the transducer. Harmonic wave generation is an acoustic phenomenon. Harmonic waves are integer multiples of the fundamental frequency. The second harmonic (twice the fundamental frequency) is currently used for tissue harmonic imaging (THI). With THI, the fundamental frequency is eliminated with image processing techniques. THI advantages include improved signal-to-noise…

Abdominal Ultrasound Imaging: Anatomy, Physics, Instrumentation, and Technique

Ultrasonography is low in cost, noninvasive, and highly portable, and it allows real-time imaging in multiple operator-controlled planes. As a result, it is the most widely used cross-sectional imaging modality worldwide. The principal challenge with ultrasonography is greater user-dependence than computed tomography (CT) or magnetic resonance imaging (MRI). Basic Physics Definition Humans can hear sound that vibrates from 20 Hertz (Hz) to 20,000 Hz. Ultrasound is the…

Fluoroscopic Study of the Abdomen and Fluoroscopic Contrast Media

Fluoroscopy is a type of imaging technique in which real-time movements of body organs and radiopaque contrast material are visualized. During a fluoroscopic examination, the operator or radiologist controls the functions of radiography equipment and x-ray tubes for real-time imaging of the patient. In abdominal imaging, fluoroscopy has a role in the diagnosis of various clinical conditions with gastrointestinal studies, postoperative studies, genitourinary studies, and more.…

Plain Radiography of the Abdomen

Technical Aspects A plain abdominal radiograph must be read with a complete knowledge of the clinical situation. The patient's history and results of the physical examination and laboratory studies are always important to evaluate an acute abdomen, which may be caused by various different diseases. Obtaining plain films with the patient supine and erect and that include the diaphragm is the classic approach. Because chest abnormalities…

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