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Inflammatory and Infectious Colonic Lesions

Etiology Colonic inflammation may be caused by numerous processes and is typically thought of as colitis. Some inflammatory conditions of the colon such as diverticulitis and epiploic appendagitis also represent inflammatory lesions of the colon and, on occasion, may be difficult to distinguish from each other and from neoplastic conditions. Colitis may be due to infection, autoimmune processes (Crohn's and ulcerative colitis), ischemia (low flow, emboli,…

Computed Tomographic Colonography

Technical Aspects Colorectal cancer is the second cause of cancer deaths in the United States, second only to lung cancer in men and breast cancer in women. Colorectal cancer screening can be used to identify adenomatous polyps, the precursor lesion to colon cancer for screening symptomatic patients. Computed tomographic (CT) colonography can be simply defined as a highly sophisticated technique that employs rigorous bowel preparation (cleansing)…

Colon Imaging: Conventional Imaging and Computed Tomography

Conventional Imaging Technical Aspects Before cross-sectional imaging, the double-contrast enema was the foremost radiologic method for detection of colonic mucosal lesions and precancerous polyps. Diagnostic high-quality double-contrast barium enema examination is an art, requiring skillful maneuvering of the patient and barium pool while optimally using fluoroscopy. With the advent of computed tomography (CT), intramural as well as extraluminal extension of colonic diseases can be detected. This…

Malignant Neoplasms and Wall Thickening of the Small Bowel

Small bowel neoplasms remain a diagnostic challenge for radiologists and clinicians. The small bowel represents 75% of the total length of the gastrointestinal tract and more than 90% of the mucosal surface, but less than 2% of all gastrointestinal malignancies originate in the small bowel. Malignant tumors of the small bowel may arise from the mucosal epithelium, lymphoid tissue, blood vessels, nerves, and muscle. Secondary involvement…

Benign Neoplasms and Wall Thickening of the Small Bowel

Normal intestinal wall thickness depends on the degree of bowel distention and the imaging modality. The normal jejunum wall thickness measures approximately 2 mm and the ileum 1 mm on enteroclysis. On computed tomography (CT), 3 mm is accepted as the upper limit of normal when the bowel is completely distended. The hallmark of benign wall thickening is homogenous or stratified wall thickening. The appearance is due to low…

Acute and Chronic Small Bowel Ischemia

Etiology Acute mesenteric ischemia of the small bowel has four major causes: (1) arterial embolism, (2) arterial thrombosis, (3) nonocclusive mesenteric ischemia, and (4) mesenteric venous thrombosis ( Table 26-1 ). Less common causes include aortic dissection, spontaneous dissection of the celiac or superior mesenteric artery (SMA), and vasculitis. The common end result is an acute reduction in splanchnic blood flow that can lead to bowel…

Small Bowel Obstruction

Small Bowel Obstruction: General Considerations Etiology Small bowel obstruction (SBO) is a common manifestation, and appropriate management continues to be a clinical challenge. The morbidity and mortality associated with acute SBO continue to be significant; however, there has been a decline in mortality from SBO in the last 50 to 60 years from 25% to 5%. The goal of treatment is to recognize the complications of…

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…