Материал: Advanced Imaging of the Abdomen - Jovitas Skucas

imaging detects no obstruction; rather, gastroparesis is suggested.

Other

Patients with chronic liver disease and portal hypertension have delayed gastric emptying of both solid and liquid emptying phases. A number of neoplasms are associated with gastroparesis, presumably representing a paraneoplastic process.

Patients with moderate to severe neurologic trauma tend not to tolerate gastric tube feedings. Using radionuclide imaging to measure gastric solid and liquid emptying, men with either spinal cord or head injury had significantly prolonged gastric emptying compared to controls (73); gastric emptying was more prolonged in those with a high-level injury compared to a low-level lesion. Gastric emptying is impaired in quadriplegics.

In some nondiabetic patients with dyspepsia symptoms and no obvious cause, scintigraphy and barium studies suggest gastroparesis and poor antral motor activity; often a barium study reveals retention of food in the stomach.

Figure 2.27. Gastric foreign body. This 3–year-old had swallowed a battery months ago; it was encased by dense fibrosis. (Courtesy of Bevin Bastian, M.D., Memorial Hospital, Rock Springs, Wyoming.)

Systemic Sclerosis

Most scintigraphy and barium studies show little if any abnormality in gastric peristalsis or emptying in patients with systemic sclerosis. In symptomatic patients with diffuse disease, however, scintigraphic gastric emptying studies using solid food often reveal delayed gastric emptying.

While esophageal and some other cancers are not uncommon in a setting of progressive systemic sclerosis, gastric cancer is exceedingly rare.

Bulimia/Anorexia Nervosa

Acute gastric dilation is a complication of anorexia nervosa during a bulimic attack.A rare sequela is gastric necrosis and perforation. A conventional radiograph should detect gastric dilation and suggest a need for close follow-up. More complex imaging is superfluous but is often obtained when evaluating abdominal symptoms in these patients, often girls or young women.

Swallowed Foreign Bodies

Most swallowed foreign bodies pass through the gastrointestinal tract. Sharp objects and objects retained in the stomach for over a day or so are generally removed endoscopically. Larger objects, including some coins, remaining in the stomach for prolonged time tend to become attached to the gastric wall and are then difficult to remove endoscopically. Some actually appear to embed in the gastric wall (Fig. 2.27).

Metal objects can corrode. In vitro studies show that radiolucent corrosion develops within 24 hours in post-1982 United States zinc alloy pennies when retained in the stomach (74); no such changes were evident in copper-based pre-1982 pennies.

Gastric Hernia

A large hiatal hernia is almost always associated with organoaxial torsion, with the degree of torsion having a direct relationship to the size of the hernia (Fig. 2.28). Up to a 180-degree twist

Figure 2.28. Intrathoracic stomach. With herniation, the stomach tends to rotate and, as in this patient, the greater curvature has rotated 180 degrees and is superior to the lesser curvature. Such a twist predisposes to gastric volvulus.

is present if most of the stomach is in the chest. In spite of the torsion, gastric volvulus develops only in a minority of these patients; a more common problem is obstruction at the hiatus.

One of the less common causes of a diaphragmatic hernia is prior surgery. As one example, transdiaphragmatic gastric herniation developed after coronary artery bypass using a right gastroepiploic artery (75).

Occasionally Tc-99m-pertechnetate scintigraphy, performed for other indications, will demonstrate an unsuspected diaphragmatic hernia.

An ulcer is not uncommon in a hiatal hernia; these ulcers are notoriously difficult to detect with a barium study (Fig. 2.29). A perforating ulcer in a hernia involves any adjacent structure, including pericardium and left ventricle. Cancers also develop in hiatal hernias (Fig. 2.30).

Table 2.5. Causes of abnormal gastric communications

To peritoneal cavity:

Acute trauma

Peptic ulcer disease

Neoplasm

Ischemia

To bowel:

Surgical anastomosis

Peptic ulcer disease

Neoplasm

Primary gastric

Primary colonic

Crohn’s disease

To biliary tree:

Gallstone disease

Peptic ulcer disease

Neoplasm

To urinary tract:

Staghorn calculus

Perforation/Fistula

A gastric fistula with communication to another organ is less common than in the small bowel or colon. Part of the reason is the relatively thick gastric wall and its relatively rich blood supply, making gastric ischemia uncommon. Nevertheless, numerous abnormal communications involving the stomach have been reported (Table 2.5).

Vascular Lesions (Bleeding)

Clinical

Prophylactic aspirin use is recommended for a number of medical conditions, yet at times even low doses result in gastrointestinal bleeding.

Hematemesis implies bleeding proximal to the ligament of Treitz. Melena, or black tarry stool, usually is from an upper gastrointestinal site but occasionally is secondary to small bowel or even right colonic bleeding (incidentally, black tarry stool is melenic stool; melanotic stool implies the presence of melanin pigment). Common causes of hematochezia and melena in adults include a duodenal or gastric ulcer. Common etiologies of upper gastrointestinal bleeding in pediatrics range from gastritis and

ADVANCED IMAGING OF THE ABDOMEN

esophagitis to peptic ulcers and varices in older children.

An occasional patient with diabetic ketoacidosis develops upper gastrointestinal hemorrhage; bleeding generally is not severe and is self-limited. The most common cause of such bleeding is erosive esophagitis, less often gastritis and duodenitis.

Although ascariasis is usually associated with small bowel and biliary disorders, upper gastrointestinal ascariasis is a rare cause of gastric bleeding.

Diffuse gastric angiomatosis manifests with bleeding, at times life-threatening. Angiography should be diagnostic. Some of these patients require a total gastrectomy.

Imaging

Several available scintigraphic techniques identify gastrointestinal bleeding. Provided active bleeding occurs at time of scanning, Tc- 99m–sulfur colloid detects bleeding rates as low as 0.1mL/min. Intermittent bleeding tends to be missed because of rapid clearance of the sulfur colloid from circulation.

Tc-99m–red blood cell scintigraphy provides a prolonged blood pool and is more useful with intermittent bleeding. Only several milliliters of extravasated blood is needed for detection. Serial images up to 24 hours are obtained. One cause of false-positive results is secretion of free Tc-99m-pertechnetate into the gastrointestinal tract.

Angiographic detection of bleeding has been largely replaced by contrast-enhanced CT, except when performed as part of therapeutic embolization.

Tumors

Chronic bleeding and resultant iron-deficiency anemia are one of the clinical presentations of gastric carcinomas. Mesenchymal tumors and lymphoma also tend to ulcerate and bleed.

Some hemangiomas also bleed. Multiple gastric hemangiomas are occasionally found in Osler-Weber-Rendu syndrome.

Dieulafoy Lesions

Over a century ago a Parisian surgeon, G. Dieulafoy, described massive gastric bleeding

from an artery close to the mucosa and the term gastric Dieulafoy’s erosion entered the French medical literature. Over the years this condition has acquired a myriad of names (Table 2.6),with current usage mostly settled on Dieulafoy lesion. Although some authors refer to these lesions as gastric vascular malformation, this terminology is sufficiently similar to arteriovenous malformation to create confusion; Dieulafoy lesions are not related to arteriovenous malformations. Little evidence suggests that these lesions represent a separate disease or syndrome.

Initially these bleeding submucosal arteries were believed to be limited to the stomach, but over the last several decades similar lesions have also been described in the small bowel and colon. It usually consists of a wide-caliber submucosal artery without histologic evidence of a true aneurysm. Etiology and pathogenesis are unknown. A vascular dysplasia, or thrombosis and necrosis of an abnormal submucosal artery are considerations, but the lack of an inflammatory reaction around many of these lesions is puzzling. Bleeding is usually through a small overlying mucosal defect. The surrounding mucosa is normal.

These lesions are found throughout the stomach, although the posterior wall lesser curvature near the cardia is a common site. They are more prevalent in elderly men. Although previously believed to be rare, these lesions come to medical attention mostly when investigating massive, often life-threatening upper gastrointestinal bleeding.

The diagnosis is made from a resected specimen. Lately, however, endoscopists have become enamored with this entity, often making the diagnosis on visual inspection only and then initiating endoscopic therapy. Typical diagnostic criteria used by endoscopists are presence of

arterial bleeding or a visible nonbleeding superficial vessel without surrounding ulceration or erosion.

Endoscopic US aids in detecting subtle Dieulafoy lesions; a vessel several millimeters in diameter is detected penetrating through the muscularis propria and extending into submucosa. Partly filling the stomach with water helps identify these vessels.

Arteriography, if performed while the lesion is bleeding, should identify a feeding vessel and site of bleeding. The appearance is different from that seen with angiodysplasia or arteriovenous malformations; neither a tuft of abnormal vessels nor an early draining vein is seen with a Dieulafoy lesion.

Initially these lesions were managed by wedge resection or oversewing, although currently many are managed by endoscopic hemostasis. Focal acute ischemia is a potential complication after sclerotherapy agent injection. Endoscopic lesion localization followed by laparoscopic gastric wedge resection is an option in some patients.

Ectasia

Gastric vascular ectasia is found in two conditions: so-called watermelon stomach and portal hypertensive gastropathy. Both are rare causes of chronic gastric bleeding and iron-deficiency anemia. Whether the underlying pathogenesis differs in a watermelon stomach from portal hypertensive gastropathy is conjecture.

Watermelon Stomach

Gastric vascular ectasia, also called watermelon stomach, is a gastropathy of uncertain pathogenesis, often associated with autoimmune gastritis and connective tissue disorders. An