Recognizing Gastrointestinal, Hepatobiliary, and Urinary Tract Abnormalities

Esophageal Carcinoma

• Esophageal carcinoma continues to have a very poor prognosis as more than 50% of patients will have metastases on initial presentation. The lack of an esophageal serosa and a rich supply of lymphatics aid in the extension and dissemination of esophageal carcinoma. Long-term alcohol and tobacco use are associated with a higher risk of esophageal carcinoma.

• Esophageal malignancies are either squamous cell carcinomas or adenocarcinomas , the latter of which is increasing in prevalence. Adenocarcinomas arise in esophageal epithelium that has undergone metaplasia from squamous to columnar epithelium (Barrett esophagus) , a process in which gastroesophageal reflux (GERD) plays a major role.

• Barium esophagrams are frequently the initial study in patients with symptoms that suggest this diagnosis, such as dysphagia ( Fig. 17.1 ).

  

Hiatal Hernia and Gastroesophageal Reflux (GERD)

• Hiatal hernias are divided into the sliding type (almost all) in which the esophagogastric junction lies above the diaphragm or the paraesophageal type (1%) in which a portion of the stomach herniates through the esophageal hiatus, but the esophagogastric junction remains below the diaphragm. In general, hiatal hernia increases in incidence with age.

• Most hiatal hernias are asymptomatic, but there is an association between the presence of some hiatal hernias and clinically significant gastroesophageal reflux.

  • Gastroesophageal reflux also occurs in patients without any visible hiatal hernia, usually because of some dysfunction of the lower esophageal sphincter that normally acts to prevent gastric acid from repeatedly refluxing into the esophagus.

Important Points

• The radiologic findings of hiatal hernia include:

  • A bulbous area of the distal esophagus containing oral contrast at the level of the diaphragm with failure of the esophagus to narrow on multiple images as it passes through the esophageal hiatus of the diaphragm

  • Extension of multiple gastric folds above the diaphragm

  • Sometimes, visualization of a thin, circumferential filling defect in the distal esophagus called a Schatzki ring ( Fig. 17.2 )

    

• Gastroesophageal reflux may be evident during fluoroscopy when barium is seen to move from the stomach retrograde into the esophagus, but reflux is intermittent so this event may not occur during the course of the examination. The absence of reflux during the study does not exclude reflux, and demonstration of reflux does not necessarily indicate the patient has the complications of GERD (i.e., esophagitis, stricture, and Barrett esophagus).

Gastric Ulcers

• In the United States, the incidence of gastric ulcer disease has been declining. In adults, infection with Helicobacter pylori accounts for almost three out of four cases of gastric ulcer disease. Nonsteroidal antiinflammatory agents account for most of the rest.

Important Points

• Most gastric ulcers occur on the lesser curvature or posterior wall in the region of the body or antrum. About 95% of all gastric ulcers are benign. The other 5% will represent ulcerations in gastric malignancies ( Fig. 17.3 ).

  

Gastric Carcinoma

• There has been a dramatic decline in the incidence of gastric carcinoma in the United States. The mortality, however, remains quite high as gastric carcinomas are frequently not diagnosed until after they have spread. Most gastric carcinomas (actually, they are adenocarcinomas) occur in the distal third of the stomach along the lesser curvature ( Fig. 17.4 ) .

  

• Double-contrast UGI images and CT scans of the abdomen can demonstrate gastric carcinomas. CT is used for staging the extent of the tumor and degree of spread.

• Other mass lesions may resemble gastric carcinoma, including leiomyomas , a benign, wall lesion that characteristically ulcerates, and lymphoma , which may produce diffusely thickened folds or multiple masses in the stomach.

Duodenal Ulcers

Important Points

• Duodenal ulcers are two to three times more common than gastric ulcers. Almost all duodenal ulcers occur in the duodenal bulb, the majority on the anterior wall of the bulb. They are overwhelmingly caused by H. pylori infection (85% to 95%).

• A double-contrast UGI series has a sensitivity that exceeds 90% in detecting duodenal ulcers ( Fig. 17.5 ).

  

• Complications of duodenal ulcers, best demonstrated by CT, include obstruction, perforation (into the peritoneal cavity) ( Fig. 17.6 ), penetration (e.g., into the pancreas), or hemorrhage.

  

General Considerations

• Opacification and distension of the bowel lumen is necessary for proper evaluation of the bowel no matter what modality is used.

Diagnostic Pitfalls

• Collapsed or unopacified loops of bowel can introduce errors of diagnosis related to an inability to visualize and differentiate real from artifactual findings or to accurately characterize the abnormality even if recognized. On CT scans of the abdomen and pelvis, unopacified loops of bowel may mimic masses or adenopathy and wall thickness is difficult to assess if the bowel is not distended.

• Therefore, orally administered contrast, frequently given in doses divided over time to allow earlier contrast to reach the colon while later contrast opacifies the stomach, is routinely utilized for most abdominal CT scans. Exceptions might include those studies performed for trauma , the stone search study for ureteral calculi, and studies specifically directed toward evaluating vascular structures, such as the aorta. Oral contrast used for CT examinations is either a dilute solution containing barium or iodinated contrast.

Important Points

• Several key findings are common to any part of the bowel and they are important to the diagnosis of bowel abnormalities by CT. All are demonstrated in Fig. 17.7 . They include:

  • Thickening of the bowel wall ( Fig. 17.7A ).

  • Submucosal edema or hemorrhage. Submucosal infiltration produces varying degrees of thumbprinting, nodular indentations into the bowel lumen representing focal areas of submucosal infiltration by edema, hemorrhage, inflammatory cells, tumor (lymphoma), or amyloid ( Fig. 17.7B ).

  • Hazy or strand-like infiltration of the surrounding fat. Extension of inflammatory reaction outside of the bowel into the adjacent fat is a sentinel finding that points to associated disease ( Fig. 17.7C ).

  • Extraluminal contrast or extraluminal air indicates the presence of a bowel perforation (see Fig. 17.6B ).

  

Crohn Disease

• Crohn disease is a chronic, relapsing granulomatous inflammation of the small bowel and colon resulting in ulceration, obstruction, and fistula formation. Crohn disease typically involves the ileum and right colon, presents with skip areas (abnormal bowel interposed between normal bowel), is prone to fistula formation , and has a propensity for recurring following surgical resection and reanastomosis in whatever loop of bowel serves as the new terminal ileum.

• Crohn disease may be imaged either with a barium small bowel follow-through (series) or CT of the abdomen and pelvis.

Important Points

• Imaging findings in Crohn disease include:

  • Narrowing, irregularity, and ulceration of the terminal ileum, frequently with proximal small bowel dilatation

  • Separation of the loops of bowel due to fatty infiltration of the mesentery surrounding the ileum making the affected loop(s) stand apart from the surrounding loops of small bowel (called a proud loop )

  • The string sign, narrowing of the terminal ileum into a near slit-like structure by spasm and fibrosis

  • Fistulae , especially between the ileum and colon but also to the skin, vagina, and urinary bladder ( Fig. 17.8 )

    

Diverticulosis

• Colonic diverticula , like most diverticula of the GI tract, represent herniation of the mucosa and submucosa through a defect in the muscular layer ( false diverticula ).

Important Points

• Colonic diverticula occur more frequently with increasing age and may be caused, at least in part, by an increase in intraluminal pressure and weakening of the colonic wall. They are usually multiple ( diverticulosis ), are almost always asymptomatic (≈90% of the time), but can become inflamed or bleed. Diverticulosis is the most common cause of massive lower GI bleeding. When they bleed, the right-sided diverticula tend to bleed more than those on the left.

• They occur most often in the sigmoid colon and are readily identified on either barium enema or CT examination as small spikes or smoothly contoured pouches attached to the colon containing either air and/or contrast ( Fig. 17.9 ).

  

Diverticulitis

• Diverticula can become inflamed and then perforate ( diverticulitis ), most often secondary to mechanical irritation and/or obstruction. CT is the modality of choice for the diagnosis of diverticulitis because the pericolonic soft tissues can be visualized with CT, which is impossible with either a barium enema or optical endoscopy.

Important Points

• CT findings of diverticulitis require the presence of at least one diverticula and include:

  • Thickening of the adjacent colonic wall (>4 mm)

  • Pericolonic inflammation : hazy areas of increased attenuation and/or streaky and disorganized linear and amorphous densities in the pericolonic fat

  • Abscess formation : multiple small bubbles of air or pockets of fluid contained within a pericolonic soft-tissue, mass-like density

  • Perforation of the colon : extraluminal air or contrast, either around the site of the perforation ( Fig. 17.10 ) or, less likely, free in the peritoneal cavity