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Imaging the Small Bowel

Traditional evaluation of the small bowel involved small bowel follow-though (SBFT) or enteroclysis, which provide excellent survey of the small bowel but are insensitive for subtle bowel pathologic processes and extraluminal abdominal findings. Within the last decade, as a result of significant advances in technology there has been a paradigm shift in the imaging evaluation of the gastrointestinal tract. With the advent of multidetector computed tomography…

Gastric Function Imaging: Technique and Applications

Technical Aspects Radionuclide gastric emptying studies (scintigraphy) remain the most widely used method for evaluation of gastric function. Radiopharmaceuticals Gastric emptying scintigraphy is most commonly performed with technetium-99m ( 99m Tc) sulfur colloid dispersed in a solid and/or liquid bolus. To be a gastric function tracer, a radioactive marker must meet certain criteria. The criteria for a good liquid-phase marker includes the ability to equilibrate rapidly…

Gastric Outlet Obstruction

Etiology Gastric outlet obstruction is an uncommon clinical consequence with a wide range of causes. Benign and malignant as well as gastric and extragastric causes have been described. It was once relatively common to see patients present with gastric outlet obstruction secondary to inflammation or scarring from peptic ulcer disease (up to 12%). Although it is difficult to define with certainty the incidence of gastric outlet…

Gastric Stromal Tumors

Stromal tumors of the stomach are rare tumors that arise from the mesenchyma, the connective tissue and blood vessels that support an organ. The parenchyma, on the other hand, represents the functional tissue of the organ. Within the stomach, the parenchyma includes the epithelial glandular tissue within the mucosa and the mesenchyma consists of the supporting tissues, or stroma. The components of the stroma include smooth…

Mucosal Diseases of the Stomach: Differentiating Benign from Malignant

Malignant Mucosal Processes Etiology A wide range of benign disease processes can affect the mucosa of the stomach, including inflammatory, infectious, hereditary, and autoimmune processes. What these processes have in common is that they affect one of the primary defenses of the stomach wall—the mucosal layer. In considering the radiologic appearance of these entities, it is helpful to divide them into their primary mucosal manifestations—ulcers, polyps…

Imaging of the Stomach and Duodenum

Technical Aspects Technique The patient is given sodium bicarbonate/dimethicone granules (Carbex), a gas-producing agent, to swallow and then drinks the E-Z HD 250% weight/volume 60 mL barium. Spot views of the esophagus are taken at the beginning (anteroposterior and right anterior oblique positions) while barium is being swallowed (if clinically indicated), and then the patient is asked to lie down on the left side (thus preventing the…

Esophageal Imaging

Technical Aspects Anatomy The esophagus extends from the pharynx to the cardiac portion of the stomach. The length of the esophagus is approximately 25 to 30 cm, and it has cervical, thoracic, and abdominal portions. The cervical portion extends from the cricopharyngeus to the suprasternal notch behind the trachea. The thoracic portion extends from the suprasternal notch to the diaphragm behind first the trachea and then the…

Acute Gastrointestinal Bleeding

Etiology The causes of upper gastrointestinal bleeding include esophageal or gastric varices, Mallory-Weiss tears, gastritis, and gastric or duodenal ulcers. Common causes of lower gastrointestinal tract bleeding include colonic diverticulosis, ischemic and infectious colitis, colonic neoplasm, benign anorectal disease, arteriovenous malformations, ischemia, and Meckel's diverticulum. Prevalence and Epidemiology Acute gastrointestinal bleeding is classified into upper and lower gastrointestinal regions based on the site of hemorrhage (proximal…

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…