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(Radiographics. 1999;19:855-872.)
© RSNA, 1999

SCIENTIFIC EXHIBITS

Congenital Anomalies of the Upper Gastrointestinal Tract1

Teresa Berrocal, MD, Isabel Torres, MD, Julia Gutiérrez, MD, Consuelo Prieto, MD, María Luisa del Hoyo, MD and Manuel Lamas, MD

1 From the Servicio de Radiodiagnóstico, Hospital Infantil "La Paz," Paseo de la Castellana 261, 28046 Madrid, Spain. Presented as a scientific exhibit at the 1997 RSNA scientific assembly. Received March 16, 1998; revision requested April 29 and final revision received September 15; accepted September 16. Address reprint requests to T.B.

Abstract

A wide spectrum of congenital anomalies may affect the upper gastrointestinal tract, including anomalies of the esophagus (eg, atresia, fistulas, webs, duplications, vascular rings), stomach (eg, congenital gastric outlet obstruction, duplications), and duodenum (eg, atresia, annular pancreas, duplications, malrotation). The evaluation of affected patients can require multiple imaging modalities for diagnosis and surgical planning. Radiography is often diagnostic and specific and can usually provide important clues to help determine the optimal diagnostic procedure. Neonates with complete gastric or upper intestinal obstruction do not usually require further radiologic evaluation after radiography: Barium studies are usually contraindicated, and complementary procedures (eg, ultrasound [US], computed tomography [CT]) are not usually helpful and may even delay surgery, resulting in death. Nevertheless, US has become important in the evaluation of the pediatric gastrointestinal tract and is being used in an increasing number of applications. CT and magnetic resonance imaging are unsuitable for general screening but provide superb anatomic detail and added diagnostic specificity. They are especially useful in demonstrating esophageal duplications and vascular rings as well as associated abnormalities. However, the decision to perform a given imaging examination should be considered carefully to avoid inconvenience or unnecessary radiation exposure to the patient or delays in surgical correction. Quality control programs should be in place to ensure safe, effective radiologic practice through use of up-to-date equipment and good imaging technique.

Index Terms: Duodenum, abnormalities, 73.143 • Duodenum, stenosis or obstruction, 73.143 • Esophagus, abnormalities, 71.141, 71.142 • Gastrointestinal tract, abnormalities, 71.14, 72.14, 73.14 • Stomach, abnormalities, 72.141, 72.143 • Stomach, stenosis or obstruction, 72.143

INTRODUCTION

The fully functional alimentary tract in the neonate is a complex organ system that develops from a simple digestive tube through a complicated but orderly series of events that span the period from very early embryonic life to birth. Because many alimentary tract abnormalities are the result of abnormal embryogenesis, an understanding of the normal development of the alimentary tract is helpful in understanding anomalous development. Congenital anomalies of the upper gastrointestinal tract may manifest during the neonatal period or later in life, even in adulthood. In general, there are certain major symptoms that lead to referral for examination of the upper alimentary tract, and the relative importance of each symptom may vary depending on the patient's age. The indications for each imaging modality and the order in which examinations are to be conducted should be considered carefully to avoid unnecessary examinations. In the radiologic examination of children, the problem of radiation protection should be addressed first and foremost, regardless of the portion of the anatomy being imaged (Appendix).

In this article, we discuss and illustrate a wide spectrum of congenital anomalies affecting the upper gastrointestinal tract and evaluate the efficacy of various imaging modalities (radiography, barium studies, ultrasound, computed tomography [CT], magnetic resonance [MR] imaging) in the diagnosis and treatment of these conditions. We discuss the embryologic and pathologic basis of radiologic findings when appropriate. In addition, we examine the pitfalls, diagnostic difficulties, and differential diagnoses associated with these imaging procedures. Finally, we address the issue of radiation protection in pediatric imaging.

ESOPHAGUS

Esophageal Atresia and Tracheoesophageal Fistula
Esophageal atresia and tracheoesophageal fistula is a complex of congenital anomalies characterized by incomplete formation of the tubular esophagus or an abnormal communication between the esophagus and trachea. The precise cause of this complex is unknown, but it is thought to be a developmental disorder in the formation and separation of the primitive foregut into the trachea and esophagus (1). Early during fetal life, the esophagus and trachea constitute a single tube that later divides into two structures through foregut lateral wall folding. If the folding process is incomplete and the lateral mesodermal walls fail to meet at any point, a tracheoesophageal fistula results. If the lateral folds turn dorsally during the development of the two structures and cut through the esophageal lumen, the result is atresia. In addition, intrauterine anoxia or stress resulting in vascular compromise may produce focal necrosis of the esophagus and result in atresia or tracheoesophageal communication (2–4). In 25% of cases, this anomaly is associated with other gastrointestinal malformations such as imperforate anus, pyloric stenosis, duodenal atresia, annular pancreas, and, less frequently, cardiac, genitourinary, and vertebral alterations (5). The VACTERL complex (vertebral, anal, cardiac, tracheal, esophageal, renal, and limb anomalies) is perhaps the best known grouping of anomalies associated with tracheoesophageal lesions (6,7).

Different types of esophageal atresia are identified on the basis of the presence (and location) or absence of a tracheoesophageal fistula. There are several systems for classifying these lesions. Figure 1 shows the classification that we and others have used (5) as well as the prevalence of each type in 333 infants seen at our institution over the past 18 years. Type A is pure esophageal atresia without fistula, type B is esophageal atresia with a fistula between the proximal pouch and the trachea, type C is esophageal atresia with a fistula from the trachea or the main bronchus to the distal esophageal segment, type D is esophageal atresia with both proximal and distal fistulas, and type E is an H-shaped tracheoesophageal fistula without atresia. Of these five types of esophageal atresia, type C is by far the most common. Esophageal atresia is generally suspected on the basis of polyhydramnios, inability to swallow saliva or milk, aspiration during early feedings, or failure to successfully pass a catheter into the stomach. Feeding difficulties with choking occur in infants with type E (fistula without atresia), but the diagnosis may not be made until several years later when the patient presents with a cough while swallowing, recurrent pneumonia, and a distended abdomen (8,9).



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  		Figure 1.  Drawings illustrate a classification scheme for esophageal atresia and tracheoesophageal fistula. A = atresia without fistula, B = atresia with upper fistula, C = atresia with lower fistula, D = atresia with both lower and upper fistulas, E = tracheoesophageal fistula with no atresia. e = esophagus, s = stomach. Types A and B are similar radiographically, as are types C and D. Prevalence of the different types of atresia in 333 cases seen at the authors' institution over the past 18 years is as follows: A, 10%; B, 0.9%; C, 53%; D, 2.1%; and E, 10%. (Reprinted, with permission, from reference 5.)

 
Radiologic diagnosis is based on findings at anteroposterior and lateral chest radiography, which reveals a blind pouch of the proximal esophagus that is distended with air. Radiographic evaluation should always include the abdomen to assess the presence of air in the gastrointestinal tract (distal fistula) (Fig 2). In types A and B, there is complete absence of gas in the stomach and intestinal tract, whereas in types C and D the gastrointestinal tract commonly appears distended with air. The type of esophageal atresia is confirmed by advancing a radiopaque feeding tube through the nose to the level of the atresia. The tube will curl when it approaches the blind end (Figs 3, 4). Atelectasis and pneumonia involving the upper right lobe are seen in up to 50% of cases. When type E (H-shaped tracheoesophageal fistula without atresia) is suspected, radiologic investigation is directed toward demonstration of the fistula, which typically courses forward and upward from the esophagus (Fig 5). Nonionic water-soluble contrast material is preferable in these patients, but a small amount of properly diluted barium can be used if necessary (2).



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  		Figure 2a.  Esophageal atresia with fistula (type D). (a) Frontal radiograph shows air within the distended upper esophageal pouch (arrows). The presence of gas in the bowel indicates fistulous communication between the lower esophageal segment and the trachea. (b) Lateral radiograph more clearly demonstrates the distended upper esophageal pouch with resulting pressure deformity of the trachea. An upper fistula was also found at surgery.

 


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  		Figure 2b.  Esophageal atresia with fistula (type D). (a) Frontal radiograph shows air within the distended upper esophageal pouch (arrows). The presence of gas in the bowel indicates fistulous communication between the lower esophageal segment and the trachea. (b) Lateral radiograph more clearly demonstrates the distended upper esophageal pouch with resulting pressure deformity of the trachea. An upper fistula was also found at surgery.

 


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  		Figures 3-5.  (3) Esophageal atresia without fistula (type A). Frontal radiograph shows a radiopaque tube curling into the upper esophageal pouch (arrows). No air is present in the gastrointestinal tract; therefore, there is no distal fistula. (4) Esophageal atresia with lower fistula (type C). On a frontal radiograph, a catheter is seen coiled within the upper esophageal pouch (arrows). Air is also present in the gastrointestinal tract, indicating communication between the lower esophageal segment and the respiratory tree. The bowel dilatation is the result of an imperforate anus associated with esophageal atresia. (5) Tracheoesophageal fistula without atresia (type E). Esophagogram shows a fistula (arrow) arising from the anterior portion of the esophagus (e) and passing cephalad to the posterior portion of the trachea (t).

 


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  		Figures 3-5.  (3) Esophageal atresia without fistula (type A). Frontal radiograph shows a radiopaque tube curling into the upper esophageal pouch (arrows). No air is present in the gastrointestinal tract; therefore, there is no distal fistula. (4) Esophageal atresia with lower fistula (type C). On a frontal radiograph, a catheter is seen coiled within the upper esophageal pouch (arrows). Air is also present in the gastrointestinal tract, indicating communication between the lower esophageal segment and the respiratory tree. The bowel dilatation is the result of an imperforate anus associated with esophageal atresia. (5) Tracheoesophageal fistula without atresia (type E). Esophagogram shows a fistula (arrow) arising from the anterior portion of the esophagus (e) and passing cephalad to the posterior portion of the trachea (t).

 


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  		Figures 3-5.  (3) Esophageal atresia without fistula (type A). Frontal radiograph shows a radiopaque tube curling into the upper esophageal pouch (arrows). No air is present in the gastrointestinal tract; therefore, there is no distal fistula. (4) Esophageal atresia with lower fistula (type C). On a frontal radiograph, a catheter is seen coiled within the upper esophageal pouch (arrows). Air is also present in the gastrointestinal tract, indicating communication between the lower esophageal segment and the respiratory tree. The bowel dilatation is the result of an imperforate anus associated with esophageal atresia. (5) Tracheoesophageal fistula without atresia (type E). Esophagogram shows a fistula (arrow) arising from the anterior portion of the esophagus (e) and passing cephalad to the posterior portion of the trachea (t).

 
Esophageal atresia may be suggested by the presence of a combination of polyhydramnios, reduced intraluminal liquid in the fetal gut, and inability to detect the fetal stomach at prenatal US (10).

Esophageal stenosis and webs may be associated with tracheoesophageal fistula and are considered a variant of esophageal atresia (11–13). Symptoms may occur at any age and are usually due to food impaction and aspiration. Congenital stenosis commonly manifests as a 2–3-mm constriction in the middle or distal esophagus (Fig 6) (14). Differential diagnosis must include strictures acquired secondary to surgery, corrosive ingestion, and (in particular) gastroesophageal reflux. Congenital webs are seen at barium studies as a smooth, thin, transverse or oblique defect in the esophagus (Fig 7a) and may be located at the same level as the fistula (Fig 7b) (13).



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  		Figures 6, 7.  (6) Congenital stenosis in a 9-month-old male infant with persistent regurgitation. Esophagogram demonstrates a small, narrowed segment in the middle third of the esophagus (arrows). (7) Congenital esophageal webs. (a) Esophagogram shows a concentric filling defect (arrows). At endoscopy, a thin diaphragm with a central opening was noted. (b) Esophagogram shows a tracheoesophageal fistula (arrow) located at the same level as a congenital stricture (arrowhead).

 


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  		Figures 6, 7.  (6) Congenital stenosis in a 9-month-old male infant with persistent regurgitation. Esophagogram demonstrates a small, narrowed segment in the middle third of the esophagus (arrows). (7) Congenital esophageal webs. (a) Esophagogram shows a concentric filling defect (arrows). At endoscopy, a thin diaphragm with a central opening was noted. (b) Esophagogram shows a tracheoesophageal fistula (arrow) located at the same level as a congenital stricture (arrowhead).

 


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  		Figures 6, 7.  (6) Congenital stenosis in a 9-month-old male infant with persistent regurgitation. Esophagogram demonstrates a small, narrowed segment in the middle third of the esophagus (arrows). (7) Congenital esophageal webs. (a) Esophagogram shows a concentric filling defect (arrows). At endoscopy, a thin diaphragm with a central opening was noted. (b) Esophagogram shows a tracheoesophageal fistula (arrow) located at the same level as a congenital stricture (arrowhead).

 
Esophageal Duplications
Duplications of the esophagus are the second most common duplication of the gastrointestinal tract after ileal duplications and account for 15%–20% of all reported duplications (15–17). Although several theories have been proposed to explain the embryologic basis for gastrointestinal tract duplications, no single hypothesis can explain all possible combinations of duplications, locations, and associated anomalies (15). The aberrant luminal recanalization theory proposed by Bremer (18) adequately explains duplications in those portions of the gastrointestinal tract that go through the "solid stage," including the esophagus, small bowel, and colon. In the 5th or 6th week of intrauterine life, the foregut is covered by cells similar to those seen in the respiratory tract. This epithelium grows and obliterates the lumen and later produces secretions that form vacuoles in the intercellular space. These vacuoles line up longitudinally and eventually coalesce to form the new lumen. If for any reason some vacuoles fail to coalesce along the longitudinal axis, a cyst will form that may migrate laterally into the esophageal wall and become surrounded by the muscular layers. Due to the elongation of the intrathoracic viscera and the dextrorotation of the stomach, these cysts are frequently found in the lower part of the esophagus on the right side. The intrauterine vascular accident theory proposed by Favara et al (19) suggests that, like small bowel atresias, gastrointestinal duplications arise from an intrauterine vascular accident during early fetal development. However, this explanation is only valid for small bowel atresias and, perhaps, their associated duplications (15).

The duplicated segment of the esophagus has a thick wall of smooth muscle and is lined with alimentary tract mucosa. This mucosal lining may be identical to that of the parallel segment or may be like that in other portions of the alimentary tract, most often gastric mucosa, in which case peptic ulceration is commonly seen in the duplication (15,20). In neonates and infants, pressure on the adjacent lung or esophagus leads to respiratory difficulties or dysphagia and vomiting.

Complete esophageal duplication is extremely rare and is often associated with gastric duplication. Visualization of the duplicated segment in the complete, tubular form of esophageal duplication depends on communication with the normal esophagus or stomach (Fig 8) and may not be appreciated until after the gastric component is surgically treated (2,21). Most esophageal duplications manifest as spheric cysts (Fig 9) located in the right hemithorax; rarely do they communicate with the esophagus. At chest radiography, they are generally seen as posterior mediastinal masses. Esophagography shows either the esophagus displaced to the side opposite the mass or an intramural, extramucosal mass. At CT, the duplication appears sharply marginated, has a homogeneous near-water attenuation, and does not enhance after intravenous administration of contrast material (22). At MR imaging, most duplications have low signal intensity on T1-weighted images and very high signal intensity on T2-weighted images (23). Recently, endoscopic US has proved to be reliable in the diagnosis of this lesion because it can demonstrate contiguity of the muscularis propria of the esophagus with the muscle layer of the cyst wall (24). However, CT and MR imaging are superior to endosonography in that they permit simultaneous imaging and evaluation of the spine, pulmonary parenchyma, airway, and adjacent structures.



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  		Figures 8, 9.  (8) Complete esophageal duplication in a 27-year-old man with a history of dysphagia and choking. Esophagogram shows the duplicated esophagus (d) located posterior to the normal esophagus. (9) Duplication cyst in a 2-year-old girl with recurrent episodes of vomiting. (a) Esophagogram shows extrinsic compression of the left wall of the esophagus (arrows). (b) On a coronal T1-weighted MR image, a sharply defined low-signal-intensity mass (arrows) is seen adjacent to the left side of the esophagus. The mass had very high signal intensity on a T2-weighted MR image (not shown).

 


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  		Figures 8, 9.  (8) Complete esophageal duplication in a 27-year-old man with a history of dysphagia and choking. Esophagogram shows the duplicated esophagus (d) located posterior to the normal esophagus. (9) Duplication cyst in a 2-year-old girl with recurrent episodes of vomiting. (a) Esophagogram shows extrinsic compression of the left wall of the esophagus (arrows). (b) On a coronal T1-weighted MR image, a sharply defined low-signal-intensity mass (arrows) is seen adjacent to the left side of the esophagus. The mass had very high signal intensity on a T2-weighted MR image (not shown).

 


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  		Figures 8, 9.  (8) Complete esophageal duplication in a 27-year-old man with a history of dysphagia and choking. Esophagogram shows the duplicated esophagus (d) located posterior to the normal esophagus. (9) Duplication cyst in a 2-year-old girl with recurrent episodes of vomiting. (a) Esophagogram shows extrinsic compression of the left wall of the esophagus (arrows). (b) On a coronal T1-weighted MR image, a sharply defined low-signal-intensity mass (arrows) is seen adjacent to the left side of the esophagus. The mass had very high signal intensity on a T2-weighted MR image (not shown).

 
Associated anomalies of the thoracic spine ranging from spina bifida and hemivertebra to vertebral fusion defects have been described (15,16,19,25); however, because thoracic spine anomalies are much more frequently associated with neurenteric cyst, their presence should first suggest this lesion. Differential diagnosis includes any posterior mediastinal mass (eg, a neoplasm arising from the sympathetic chain), bronchogenic or neurenteric cysts, pulmonary sequestration, anterior meningocele, and hemangioma (17).

Vascular Compression of the Esophagus
Compression and displacement of the esophagus as a result of anomalous development of the aorta and its branches are not uncommon in the pediatric patient. Although most cases are asymptomatic, respiratory and gastrointestinal symptoms may occur. The most frequent anomalies causing dysphagia are the double aortic arch, the right aortic arch with a left ligament arising from the descending aorta, and an aberrant right subclavian artery arising on the left and passing posterior to the trachea or retroesophageal right subclavian artery (26). The two aortic arch anomalies are true, complete vascular rings and frequently cause dysphagia lusoria. Rarely does one find a significant esophageal dysfunction associated with an aberrant retroesophageal right subclavian artery; it does not constitute a true vascular ring and should be viewed as a persistence of the right-sided aortic elements (27).

The diagnosis and differentiation of distinct vascular anomalies are based primarily on findings at chest radiography in association with those at esophagography. The actual vascular anatomy may be demonstrated with echocardiography, CT, or MR imaging (28). Occasionally, arteriography may be required for clarification or preoperative demonstration of the vascular anatomy.

The most common (and serious) type of complete vascular ring is the double aortic arch, which consists of an anterior and a posterior arch encircling the trachea and esophagus in a tight ring and joining to form a common descending aorta (29,30). Affected patients usually have severe respiratory symptoms and some difficulty swallowing. Chest radiography is rarely diagnostic in infants, but bilateral indentation of the trachea may be visible in older children. A barium examination is often diagnostic (Fig 10) and demonstrates a horizontal defect on the posterior wall of the esophagus at the level of the third or fourth thoracic vertebra. This defect is formed by the posterior arch (usually the larger of the two arches) as it passes behind the esophagus. On an anteroposterior esophagogram, there are bilateral compressions that produce a reverse S-shaped indentation of the esophagus (31).



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  		Figure 10a.  Double aortic arch. Anteroposterior (a) and lateral (b) barium esophagograms show posterior indentation of the upper esophagus bilaterally (arrows).

 


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  		Figure 10b.  Double aortic arch. Anteroposterior (a) and lateral (b) barium esophagograms show posterior indentation of the upper esophagus bilaterally (arrows).

 
A right aortic arch with a left ligament arising from the descending aorta is another type of vascular ring but is much less common than the double aortic arch. The left ligament of Botallo passes from the left pulmonary artery to the descending aorta or left subclavian artery, coursing to the left of the trachea and esophagus. These structures may be compressed by the ring formed by the aorta, the pulmonary artery, and the ligament. In this anomaly, the origin of the left subclavian artery is frequently dilated (diverticulum of Kommerell) (32). Symptoms and radiographic findings are identical to those associated with the double aortic arch. The right aortic arch is identified at contrast material–enhanced radiography by the indentation it makes on the right lateral wall of the esophagus, and the ligament of Botallo is identified by its impression on the anterolateral wall of the esophagus. This anomaly can be well demonstrated with CT or MR imaging, but angiography may be required for investigation of associated intracardiac defects and surgical planning (33).

The most common of the aortic arch anomalies is an aberrant right subclavian artery originating from an otherwise normal left aortic arch (34). This anomaly occurs in nearly 1% of the population. The anomalous vessel arises from the left side of the aortic arch and crosses the mediastinum obliquely from left to right behind the esophagus and trachea on its cephalic course, producing a characteristic and pathognomonic indentation on the esophagus (2,35,36). At esophagography, this indentation is seen as an oblique filling defect extending from left to right (Fig 11). Except for occasional mild dysphagia, the condition rarely causes symptoms, and further radiologic examination is usually unnecessary.



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  		Figure 11a.  Aberrant right subclavian artery. (a) Anteroposterior esophagogram shows an oblique filling defect passing cephalad from left to right (pathognomonic indentation) (arrows). (b) Lateral esophagogram shows compression of the posterior wall of the esophagus (arrow).

 


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  		Figure 11b.  Aberrant right subclavian artery. (a) Anteroposterior esophagogram shows an oblique filling defect passing cephalad from left to right (pathognomonic indentation) (arrows). (b) Lateral esophagogram shows compression of the posterior wall of the esophagus (arrow).

 
STOMACH

Developmental Obstructive Defects
Unlike the esophagus, the stomach undergoes little alteration in form during development. None of the malformations to which the stomach is subject is common, and hypertrophic pyloric stenosis, the only serious gastric disorder seen frequently in infancy, is not of embryonic origin.

Complete obstruction involving the gastric outlet is a rare condition that is usually due to gastric atresia, although it may be caused by extrinsic pressure from congenital peritoneal bands or by annular pancreatic tissue in the gastric wall (2). Gastric atresia accounts for less than 1% of all congenital intestinal obstructions and is limited to the antrum and pyloric region. Congenital obstructions are thought to be due to localized vascular occlusion in fetal life rather than to failed recanalization because there is no epithelial perforation in the stomach comparable to that in the esophagus or duodenum. The atresia is usually produced by a membranous diaphragm that only affects the mucosa, although there may be more extensive obliteration of the lumen (37). Gastric atresia may be familial or associated with epidermolysis bullosa. The predominant symptom is regurgitation of bile-free vomitus within the first few hours after birth. Abdominal radiography shows distention of the stomach proximal to the obstruction and the absence of gas in the small bowel and colon, resulting in a "single bubble" appearance (Fig 12). Contrast-enhanced imaging is unnecessary, and most patients are taken directly to surgery (2,38).



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  		Figure 12.  Pyloric atresia in a male neonate. Frontal radiograph shows distention of the stomach and absence of gas in the small bowel (single bubble appearance).

 
In partial gastric outlet obstruction, symptoms may not appear until childhood or even adulthood. The most common presenting symptoms are cyclic postprandial vomiting and episodes of transient vomiting. The most frequent cause is incomplete prepyloric diaphragm, an incomplete form of atresia. Antral stenosis, aberrant pancreatic tissue in the gastric antrum, and antral duplication cysts can also cause partial gastric outlet obstruction. Radiography shows distention of the stomach and decreased gas in the small bowel, the extent of which depend on the degree of obstruction (Fig 13). Barium studies and US should help identify the defect. An incomplete prepyloric membrane is seen at barium studies as a thin (2–3-mm), linear filling defect traversing the barium column (Fig 14) (39). At US, the diaphragm appears as an echogenic band extending centrally from the lesser and greater curvatures in the prepyloric region (40–42). Ectopic pancreatic tissue may be found at various sites in the gastrointestinal tract, most commonly the gastric antrum. An upper gastrointestinal series shows a smooth, dome-shaped filling defect 1–3 cm in diameter on the larger curvature (Fig 15), and at times central umbilication may be seen (43). Pancreatic ectopic tissue may prolapse into the pylorus, producing intermittent obstruction (44,45).



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  		Figure 13.  Congenital antral stenosis in a 1-month-old male infant with vomiting attacks from birth. Frontal radiograph shows distention of the stomach and decreased gas in the small bowel. Findings at pylorus US were normal.

 


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  		Figure 14.  Incomplete antral web. Radiograph from a barium study (anterior oblique view) shows a concentric radiolucent band (arrows) producing discrete antral lumen reduction. Arrowhead indicates pylorus.

 


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  		Figure 15.  Ectopic pancreas in the gastric antrum. Image from an upper gastrointestinal series shows a rounded nodular defect in the gastric antrum with central umbilication identified by a fleck of barium (arrow). The diagnosis was confirmed at surgery.

 
Gastric Duplications
Duplications of the stomach account for about 7% of gastrointestinal tract duplications. Most are noncommunicating, spheric or ovoid closed cysts, and the most common site is the greater curvature (Fig 16) (46). The mucosal lining is usually gastric, but pseudostratified respiratory epithelium and pancreatic tissue have been found (47). Only the small gastric cysts lying within the submucosa or the muscularis propria can be explained by Bremer's theory (18) of persistent vacuoles within the primitive foregut epithelium. Larger duplications, and certainly all those lying outside the normal stomach wall, are the result of faulty endoderm and notochord separation early in development as described by McLetchie et al (48) and others. The clinical picture produced by gastric duplications depends on their size and location as well as the presence of communication with the rest of the alimentary tract. Most duplications are discovered in infants; vomiting and abdominal pain are the predominant clinical findings, although patients are frequently asymptomatic.



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  		Figure 16a.  Gastric duplication cyst. (a) Image from a contrast-enhanced upper gastrointestinal series demonstrates an intraabdominal mass displacing the stomach and bowel to the right. (b) CT scan through the gastric body shows a near-water-attenuation spheric mass (arrows) in close contact with the greater curvature of the stomach. There is no communication between the cystic lumen and the true stomach lumen. This is the least common of the enteric duplications.

 


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  		Figure 16b.  Gastric duplication cyst. (a) Image from a contrast-enhanced upper gastrointestinal series demonstrates an intraabdominal mass displacing the stomach and bowel to the right. (b) CT scan through the gastric body shows a near-water-attenuation spheric mass (arrows) in close contact with the greater curvature of the stomach. There is no communication between the cystic lumen and the true stomach lumen. This is the least common of the enteric duplications.

 
Radiography and barium studies usually show a paragastric mass displacing the stomach and bowel. US and CT show a well-defined cystic mass lying close to the greater curvature of the stomach. The presence of an echogenic inner rim and hypoechoic outer muscle layers is highly suggestive of a duplication (49,50). Complete tubular duplication of the pylorus (Fig 17) is rare: A review of 281 lesions at all levels of the gastrointestinal tract revealed only one case of this anomaly (51). As in duplications at any level of the digestive tube, ectopic gastric mucosa can be found in the duplicated pyloric channel, and peptic ulceration of this ectopic mucosa can explain unusual and often misleading symptoms.



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  		Figure 17a.  Complete pyloric duplication in a 32-year-old man with epigastric pain. (a) Image from an upper gastrointestinal series demonstrates principal (p) and duplicated (d) pyloric canals between the stomach and duodenum. Ulceration (arrow) caused the patient's symptoms. (b) Endoscopic images of the gastric outlet show two pyloric orifices.

 


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  		Figure 17b.  Complete pyloric duplication in a 32-year-old man with epigastric pain. (a) Image from an upper gastrointestinal series demonstrates principal (p) and duplicated (d) pyloric canals between the stomach and duodenum. Ulceration (arrow) caused the patient's symptoms. (b) Endoscopic images of the gastric outlet show two pyloric orifices.

 
DUODENUM

Duodenal Obstruction
Complete duodenal obstruction is seen much more frequently than congenital gastric obstruction. At clinical examination, vomiting is severe but abdominal distention is not a conspicuous feature. Vomiting is usually delayed until after the first feeding but increases progressively thereafter. Vomitus is generally bile stained because the obstruction is usually below the ampulla of Vater. The classic radiographic finding is the so-called double bubble sign (Figs 18, 19) in which the higher, larger bubble to the left side is the stomach and the other bubble is the dilated proximal duodenum, which is seen above the area of obstruction (52). No air is seen more distally in the gastrointestinal tract. Neonates showing evidence of complete duodenal obstruction at abdominal radiography rarely require further radiologic investigation. An upper gastrointestinal series provides no additional information, and there is a potential hazard of vomiting with barium aspiration (53–55). Frequent vomiting can result in lack of air in the obstructed segment; in such cases, a small amount of air can be injected via a nasogastric tube to confirm the diagnosis (38).



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  		Figures 18, 19.  (18) Duodenal atresia in an 8-hour-old female neonate who presented with bilious vomiting. Abdominal scout radiograph shows a markedly distended stomach and duodenum with no gas in the rest of the intestinal tract (double bubble sign). (19) Annular pancreas in a male neonate. Lateral radiograph shows complete duodenal obstruction with the double bubble sign, a finding that is indistinguishable from duodenal atresia.

 


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  		Figures 18, 19.  (18) Duodenal atresia in an 8-hour-old female neonate who presented with bilious vomiting. Abdominal scout radiograph shows a markedly distended stomach and duodenum with no gas in the rest of the intestinal tract (double bubble sign). (19) Annular pancreas in a male neonate. Lateral radiograph shows complete duodenal obstruction with the double bubble sign, a finding that is indistinguishable from duodenal atresia.

 
Duodenal obstruction is usually caused by duodenal atresia, annular pancreas, and midgut volvulus. Less frequently, it may be secondary to duodenal web, Ladd bands, or preduodenal portal vein. Duodenal atresia is the most important cause of complete duodenal obstruction. The cause of this condition is thought to be failure of recanalization of the duodenum between approximately the 9th and 11th weeks of gestation. Unlike jejunal and ileal atresia, this condition does not appear to be related to intrauterine vascular accidents (56). Major associated anomalies are present in about 50% of cases. Approximately 30% of patients have Down syndrome. Other anomalies include malrotation of the small bowel, esophageal atresia, congenital heart disease, imperforate anus, small bowel atresia, biliary atresia, annular pancreas, and renal anomalies (5,23,54). Annular pancreas is an anomalous band of pancreatic tissue that arises from the head of the pancreas and encircles the second portion of the duodenum. It is believed to result from the failure of normal pancreatic tissue to rotate around the duodenum. If a complete ring is formed, there may be total obstruction of the duodenum at the time of birth; if the ring is incomplete, obstruction may occur later in life or may never produce symptoms (54,55). Midgut volvulus is the most dramatic consequence of intestinal malrotation. When present at birth, midgut volvulus has a classic radiographic finding of partial obstruction of the duodenum, but evidence of complete obstruction may also be present. In such cases, it is impossible to distinguish midgut volvulus from duodenal atresia. Any duodenal obstruction that occurs after the immediate postnatal period should be assumed to be midgut volvulus until proved otherwise (38).

Prenatal diagnosis of duodenal obstruction is based on sonographic demonstration of polyhydramnios in conjunction with a fluid-filled "double bubble" in the fetal abdomen (57,58) corresponding to the double bubble sign seen on postpartum radiographs. Because there is a high prevalence of associated anomalies, the presence of the double bubble sign should prompt consideration of fetal karyotyping and a careful search for other fetal anomalies (10).

Partial duodenal obstruction may be produced by duodenal stenosis, duodenal web, Ladd bands, midgut volvulus, annular pancreas, preduodenal portal vein, and duplication cyst. Radiography shows gaseous distention of the stomach and duodenum with a normal or diminished quantity of gas in the small bowel. Barium studies are needed to differentiate between a complicated malrotation (midgut volvulus) and partial duodenal obstruction caused by a web (Fig 20) or stenosis (53). When a volvulus is present, the small intestine appears to twist like a corkscrew around the superior mesenteric artery. US may also help establish the cause in cases of malrotation and duplication cysts. Pracros et al (59) described the "whirlpool" sign of actual midgut volvulus in which clockwise wrapping of the superior mesenteric vein and mesentery around the superior mesenteric artery can be visualized at color Doppler US (60).



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  		Figure 20.  Duodenal web in a 1-year-old boy with a history of intermittent vomiting. Radiograph from a barium study shows dilatation of the stomach and proximal duodenum. An incomplete diaphragm was found at surgery.

 
When the degree of obstruction is minimal, the congenital anomaly will remain asymptomatic until adulthood or will be diagnosed incidentally when the patient undergoes examination for another condition (Fig 21).



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  		Figure 21.  Nonobstructing duodenal diaphragm in a 32-year-old man. Radiograph from a barium study shows a smooth, transverse filling defect in the second portion of the duodenum (arrows), allowing free passage of contrast material to the small bowel.

 
Duodenal Duplications
Duplications of the duodenum are usually noncommunicating and located along the first and second portions of the duodenum on the mesenteric side. Embryologic development and pathologic characteristics are similar to those described for esophageal and gastric duplications. Clinically, duodenal duplications normally manifest with symptoms of obstruction, but due to their location they may cause biliary obstruction and pancreatitis (61). At barium examinations, the duodenum usually appears to be compressed by a mass in the concavity of the duodenal c-loop (Fig 22). US, CT, and MR imaging can provide more information about the cystic nature of this lesion, which must be differentiated from a choledochal cyst or pancreatic pseudocyst (62).



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  		Figure 22a.  Duodenal duplication cyst. (a) Radiograph from a barium study shows a large filling defect on the medial border of the duodenum displacing and indenting the lumen. (b) Sonogram demonstrates a large, sonolucent cyst with a characteristic echogenic inner mucosal layer and an anechoic underlying muscular layer. Q = cyst, V = gallbladder.

 


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  		Figure 22b.  Duodenal duplication cyst. (a) Radiograph from a barium study shows a large filling defect on the medial border of the duodenum displacing and indenting the lumen. (b) Sonogram demonstrates a large, sonolucent cyst with a characteristic echogenic inner mucosal layer and an anechoic underlying muscular layer. Q = cyst, V = gallbladder.

 
CONCLUSIONS

Radiologic investigation continues to be one of the most important sources of information for the clinician in the evaluation of congenital gastrointestinal disorders, but the need for these examinations should be weighed carefully to avoid inconvenience to the patient, unnecessary exposure to radiation, or delays in surgical correction. Congenital anomalies of the upper gastrointestinal tract may manifest during the neonatal period or later in life—even during adulthood—and are usually detected in neonates only when they are the direct cause of obstruction. The most valuable aid in determining whether obstruction is present is the scout radiograph. Radiography is often diagnostic and specific; even when it is not, however, it can still provide important diagnostic clues to help determine optimal diagnostic procedure. In esophageal atresia, anteroposterior and lateral radiography of the chest and abdomen usually provides presumptive evidence of the type of abnormality. Neonates with complete gastric or upper intestinal obstruction do not usually require further radiologic evaluation after radiography: Barium studies are usually contraindicated, and complementary procedures such as US or CT do not usually provide additional information and may even delay surgery, resulting in death.

An upper gastrointestinal series must be performed in all patients with incomplete high obstruction to identify its cause because management is different in each case.

US has become an important diagnostic tool in the evaluation of the pediatric gastrointestinal tract and is being used in an increasing number of applications. In incomplete gastric outlet obstruction following the neonatal period, US is useful in differentiating a congenital anomaly from hypertrophic pyloric stenosis. US is also useful in the diagnosis of enteric duplication cysts. Demonstration of a cystic mass with an echogenic inner mucosal layer and a hypoechogenic outer muscle layer is diagnostic of an enteric duplication cyst. In cases of malrotation, the relative positions of the superior mesenteric artery and vein are correctly evaluated with US, and the whirlpool sign of midgut volvulus is visible at color Doppler US.

CT and MR imaging are unsuitable for general screening because of the need for patient sedation and monitoring, but they do provide superb anatomic detail and added diagnostic specificity. They are especially useful in demonstrating esophageal duplications and vascular rings as well as associated abnormalities. Some of these anomalies can remain asymptomatic, in which case diagnosis is the result of incidental findings at routine examination for other conditions in adulthood.

APPENDIX: RADIATION PROTECTION IN INFANTS AND CHILDREN

Children are at greater risk for late manifestations of detrimental radiation effects than are adults. For certain detrimental effects, it is estimated that radiation exposure during the first 10 years of life poses a lifetime risk three to four times greater than that associated with exposure between the ages of 30 and 40 years and five to seven times greater than that associated with exposure after the age of 50 years (63). Therefore, it is essential to develop appropriate radiation protection measures in the field of diagnostic radiology for pediatric patients.

The two basic principles of patient radiation protection as recommended by the International Commission on Radiological Protection are justification and optimization of the procedure. It is accepted that no diagnostic exposure is justifiable without a valid clinical indication, no matter how well the imaging examination is performed. Justification also implies that the necessary result cannot be achieved with other methods that would involve lower risk for the patient. Every examination must result in a net benefit for the patient (64). Justification also requires that an individual who is trained and experienced in radiologic techniques and radiation protection take overall clinical responsibility for an examination. This person should work closely with the referring physician to establish the most appropriate procedure for patient management and therapy.

Once the diagnostic examination has been clinically justified, the subsequent imaging process must be optimized. The optimal use of ionizing radiation involves the interplay of three important aspects of the imaging process: the diagnostic quality of the radiographic image, the radiation dose to the patient, and the choice of radiographic technique. These aspects are discussed in greater detail in a number of publications by international organizations (65–67).

Quality control programs for x-ray imaging equipment should form an essential part of dose-effective radiologic practice, and in every medical x-ray facility these programs should cover the most important physical and technical parameters associated with the types of x-ray examinations being performed.

The recent development of materials for cassettes, grids, tabletops, and front plates of film changers that contain carbon fiber and some new plastics has significantly reduced radiation doses to patients. This reduction is most significant in the radiographic voltage range recommended for pediatric patients and may reach 40%. Use of these materials should be encouraged.

Patient positioning must be exact regardless of whether the patient cooperates. In infants and younger children, immobilization devices must be properly applied to ensure that the patient does not move and the film is obtained in the proper projection, as well as to enable correct centering of the beam, accurate collimation to limit the field size exclusively to the required area, and shielding of the remainder of the body.

Appropriate field size is one of the most important aspects of proper radiographic technique in pediatric patients. A field that is too small will immediately degrade the respective image criteria. A field that is too large will not only impair image contrast and resolution by increasing the amount of scattered radiation but will also result in unnecessary irradiation of the body outside the area of interest. In pediatric patients, appropriate field size should be apparent from the rims of unexposed film and is of particular importance because beam-limiting devices that automatically adjust the field to the full size of the cassette are inappropriate. Discrepancies between the radiation beam and the light beam must be avoided with periodic assessment. Even minimal deviations may have a large effect in relation to the typically small field of interest.

For all pediatric examinations, good radiographic technique includes use of standard equipment for lead-rubber shielding of the anatomic areas in immediate proximity to the diagnostic field. Special shields must be added for certain examinations to protect against external scattered and extrafocal radiation. Whenever possible, the gonads should be protected in "hot" examinations (ie, those in which the gonads lie within or less than 5 cm away from the primary beam) without sacrificing necessary diagnostic information. It is best to make one's own lead contact shields for girls and lead capsules for boys. With properly adjusted capsules, the absorbed dose in the testes can be reduced by up to 95%. In girls, shadow masks within the diaphragm of the collimator are as efficient as direct shields.

Knowledge and correct use of appropriate radiographic exposure factors (eg, radiographic voltage, nominal focal spot value, filtration, film-focus distance) is necessary because these factors have a considerable impact on patient doses and image quality. Permanent parameters of the apparatus such as total tube filtration and grid characteristics should also be taken into consideration. Normally, a nominal focal spot value between 0.6 and 1.3 is suitable for pediatric patients. When bifocal tubes are available, one should use the nominal focal spot value that allows the most appropriate setting for exposure time and radiographic voltage at the chosen film-focus distance.

The soft part of the radiation spectrum that is completely absorbed by the patient is useless for image production and contributes unnecessarily to patient dose. A portion (but not enough) of this radiation is eliminated by the inherent filtration of the tube, tube housing, collimator, and so on. Most tubes have a minimum inherent filtration of 2.5 mm of aluminum. Additional filtration can further reduce unproductive radiation and thus the patient dose. For pediatric patients, the total radiation dose must be kept low, particularly when high-speed screen-film systems or image intensifying techniques are used. Not all generators allow the short exposure times that are required for higher kilovoltage techniques. Consequently, low radiographic voltage is frequently used for pediatric patients, resulting in relatively higher patient doses. Adequate additional filtration allows the use of higher radiographic voltage with the shortest available exposure times, thus overcoming the limited capability of such equipment for short exposures and allowing the use of high-speed screen-film systems and image intensifier photography. For pediatric patients, all tubes—whether in stationary, mobile, or fluoroscopic equipment—should allow filtration to be increased or easily changed as needed. Usually, additional filtration of up to 1 mm of aluminum plus 1–2 mm of copper is appropriate.

In infants and young children, the use of a grid or other antiscatter measures is usually unnecessary. Imaging without a grid will help prevent excessive patient radiation dose. Only fluoroscopic equipment with the potential for quick and easy removal of the grid should be used in these patients. Removable grids are desirable not only for fluoroscopic work; ideally, all equipment used for pediatric patients should have this capability. In addition, in any fluoroscopic examination the patient-to-film and patient-to-image intensifier distances should be kept to a minimum to reduce patient dose. This is particularly important with use of automatic brightness control, which must be switched off during fluoroscopic examinations when there are relatively large areas of positive contrast material to avoid excessive dose rates.

In pediatric imaging, exposure times must be short because young patients do not cooperate and are difficult to restrain. These short times are possible only with use of powerful generators and tubes as well as optimal rectification and accurate time switches. The equipment must function properly and must provide constancy in the shortest time range. Among the technical parameters, the use of higher-speed screen-film systems has the greatest impact on dose reduction. In addition, it allows shorter exposure times and minimizes blurring due to motion, which is the leading cause of blurring in pediatric imaging. The reduced resolution of higher-speed screens is comparatively insignificant in most clinical situations. Speed classes of 200 and above usually require the use of rare-earth or equivalent intensifying screens.

Pulsing the x-ray film during fluoroscopy (pulsed fluoroscopy) can reduce the total radiation exposure to pediatric patients undergoing conventional fluoroscopy. Pulsed progressive fluoroscopy reduces radiation dose simply by reducing the amount of time that the x-ray beam is turned on. Pulsed fluoroscopy can be accomplished only with a digital system that provides frame fill-in (ie, the repeated display of a frame from memory) (68). In many fluoroscopic procedures, optimal image quality is not needed over most of the field of view. Region-of-interest imaging is a technique for retaining optimal image quality within a region of interest while an x-ray beam filter is used to substantially reduce patient exposure peripheral to the region of interest with an acceptable increase in quantum noise (69). The basic principle involves modulation of the irradiating x-ray beam so that the intensity of photons is highest where they are needed for optimal image quality and lowest in the part of the image that is used only for reference (70). The benefits of region-of-interest imaging can be realized by using standard imaging equipment. Region-of-interest imaging has been clinically applied in gastrointestinal radiology and interventional procedures. In gastrointestinal procedures, region-of-interest fluoroscopy without image processing can be used without adversely affecting the procedure or interfering with spot radiography and can reduce the dose-area product by a factor of 1.7 (71).

Footnotes

CME FEATURE This article meets the criteria for 1.0 credit hour in category 1 of the AMA Physician's Recognition Award. To obtain credit, see the questionnaire on pp 1029–1036.

LEARNING OBJECTIVES After reading this article and taking the test, the reader will: • Understand the embryology and basic anatomy of congenital anomalies of the upper gastrointestinal tract. • Recognize the appearance of each anomaly at radiography, barium studies, US, CT, and MR imaging. • Understand the merits and pitfalls of each imaging modality. • Understand how imaging techniques can help radiologists improve the quality and costeffectiveness of medical care.

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