Diagnostic Imaging Europe
January/February 1998

Training & Education:
Chest x-rays illuminate gastrointestinal cases

By Jesus De La Torre Fernández, M.D.

A plain chest x-ray is the most commonly performed radiological procedure. Conventional x-ray makes up at least 40% of all imaging procedures conducted by a radiodiagnostic service.¹ Indicated in the protocols for many thoracic and nonthoracic pathologies, x-ray is routinely performed prior to surgery.

A chest radiograph, when properly obtained, includes the area of the abdomen below the diaphragm. The intrathoracic location of the esophagus and the natural contrast provided by air in the alimentary tract mean that additional information on the gastrointestinal tract can be provided.

The Radiologic Clinics of North America has devoted a volume to nonpulmonary aspects in chest radiography, and in the foreword, Dr. K.R. Kattan stresses the importance of assessing all the information furnished by plain chest films, not just the information on the cardiopulmonary system.² A brief review of the most important findings for gastrointestinal pathologies in plain chest x-rays follows.

Esophageal Diseases

In advanced stages of achalasia, the dilated esophagus displaces the azygoesophageal recess to the right, pushing the trachea forward. If the radiograph is taken with the patient in an upright position, retained fluid and food may demonstrate an air-fluid level (Figure 1). The absence of the gastric air bubble is another sign that may be visible.^3,4

Fifty percent of cases of systemic sclerosis involve the esophagus, and radiographs demonstrate a dilated, air-filled esophagus without peristaltic action and without visualization of an air-fluid level, because there is no obstruction. Chest radiographs also show lung abnormalities in 25% to 50% of confirmed cases. The most frequent finding is interstitial fibrosis.⁵

Esophageal diverticula may occur in the cervical esophagus (Zenker’s diverticulum), mid-esophagus (traction), or distal esophagus near the gastroesophageal junction (epiphrenic). When large, they may be mass-like and displace mediastinal interfaces and lines on chest x-rays.

Leiomyoma is the most common benign tumor of the esophagus. When large, these tumors may be visible as a mass. The following are a series of useful findings for diagnosing carcinoma of the esophagus on chest radiographs:^6-8

• displacement of the azygoesophageal recess (carcinomas in the middle and lower thirds);
• widened mediastinum;
• posterior tracheal indentation and/or mass or tracheal deviation (upper and middle thirds);
• thickening of the posterior tracheal stripe to measure more than 4.5 mm (upper and middle thirds);
• a retrocardiac or retrohilar mass;
• abnormal gastric air bubble (gastroesophageal junction); and
• prestenotic dilatation of the esophagus, with or without an air-fluid level.

Thickening of the posterior tracheal stripe may be caused by periesophageal lymphatic involvement, direct invasion by the tumor, or the tumor mass itself, and is regarded as an early sign. In a review of 20 patients with carcinoma of the esophagus, this sign was visible on radiographs as early as six months before diagnosis in at least 50% of the cases considered.⁹

Esophageal duplications account for around 20% of all gastrointestinal tract duplications. They do not normally communicate with the esophageal lumen. About 23% of duplications are located in the cervical portion, 17% in the middle third, and 60% in the distal third. Those in the distal third are often asymptomatic and are detected as incidental findings in chest radiography. They manifest as masses with soft-tissue density in the posterior mediastinum (Figure 2). When they communicate with the esophagus, they may show an air-fluid level. Esophagography may demonstrate displacement of the esophagus by a paraesophageal or intramural mass.¹⁰

Chest radiography findings of esophageal varices have been investigated in a series of 352 patients with portal hypertension.¹¹ Plain films were able to suggest up to 8% of cases. Findings included posterior mediastinal masses with displacement of the azygoesophageal recess, obliteration of the descending aorta contour, and mass density adjacent to the descending aorta appearing intraparenchymal.

After radical or partial esophagectomy, reconstruction of the tube may involve colonic, gastric, or jejunal interposition, resulting in changes in the appearance of the mediastinum. The usual procedures are colonic interposition (substernally, subcutaneously, or in the middle mediastinum) and gastric interposition (in the middle mediastinum or substernally).

Causes of esophageal perforation include iatrogenic injury (dilatation or endoscopy), spontaneous rupture (Boerhaave’s syndrome), tumor, and trauma. Findings on plain chest films are highly suggestive of perforation in at least 90% of cases, and findings include pneumomediastinum, subcutaneous emphysema, and mediastinitis. Other findings are pleural effusions, pneumothorax, and hydropneumothorax. The pleural effusion in perforation of the midesophagus tends to be right-sided, while in perforation of the distal esophagus it is usually left-sided.³

Diaphragmatic Hernias

Morgagni hernias result in the failed fusion between the fibrotendinous elements of the sternal and costal parts of the diaphragm. They usually involve the omentum and transverse colon, but the stomach, small bowel, and liver may also herniate. They typically appear in adults and are most often right-sided. Radiologically they appear as a solid mass in the right cardiophrenic angle. Air bubbles may be present (Figure 3).¹²

A Bochdalek hernia is a congenital postlateral defect in the diaphragm occurring in one of 2200 live births. It results from failure of the pleuroperitoneal membrane to close the pleuroperitoneal canal. The stomach, spleen, colon, or small bowel may be involved. Herniation is left-sided in 90% of cases. There may be hypoplasia of the lungs, which will be more severe the earlier herniation occurs during fetal development. In adults it is usually asymptomatic, appearing as a left-sided posterolateral mediastinal mass.¹²

In traumatic diaphragmatic hernias, rupture is left-sided in 90% of cases. Plain chest radiographs are usually abnormal in 95% of cases. Findings may be suggestive or diagnostic.¹³ Suspicious findings include elevated hemidiaphragm, pleural effusion, platelike atelectasis above an indistinct diaphragm, and contralateral mediastinal shift. Suggestive findings include loss of the normal contour of the diaphragm and gas bubbles, air-fluid levels, or other unusual shadows above the diaphragm. Pathognomonic findings include demonstration of supradiaphragmatic bowel or stomach.

Other Pathologies

In the gallbladder, calcifications in the form of stones or “porcelain” gallbladder may be demonstrated. Intraluminal and intramural gas may also allow detection of acute emphysematous cholecystitis.

Acute pancreatitis produces abnormalities in chest radiographs in up to 49% of patients. The most common are left-sided plate-like atelectasis and pleural effusions. Other findings include parenchymal infiltrates, pulmonary infarction, pulmonary edema, and elevation of the left hemidiaphragm. Patients may present such complications as adult respiratory distress syndrome.^3,4

The stomach and colon may be visible on chest radiographs due to the contrast produced by the air they contain. As a result, it may be possible to detect dilatation and thickening of the organs’ walls caused by inflammation or neoplasms.

As for the abdominal cavity, upright chest x-rays are the first imaging method used in patients with acute abdomen in which perforation of hollow viscera is suspected. Pneumoperitoneum is seen as curvilinear air-hyperlucent areas beneath the domes of the hemidiaphragms.³

Upper abdominal abscesses may also be detected. Usually a complication of abdominal surgery, they are most commonly located in the right subphrenic space. Pleural effusions and an elevated hemidiaphragm are the most frequent findings, and are present in 80% of cases. Visualization of extraluminal gas in the abscess occurs in 70% of cases.¹⁴

Plain chest x-rays may be useful in demonstrating certain pathologies of the gastrointestinal tract or secondary complications. Proper interpretation may be critical to patient prognosis in cases of previously undetected or unsuspected conditions.

References

1. Ravin CE. Introduction to chest radiography. In: Putman CE, Ravin CE. Textbook of diagnostic imaging. Philadelphia: W.B. Saunders 1988:413-424.
2. Kattan KR. Foreword and dedication. Radiol Clin N Am 1984;22:461.
3. Cole TJ, Turner MA. Manifestations of gastrointestinal diseases on chest radiographics. RadioGraphics 1993;13:1013-1034.
4. Gegaudas-McClees RK, Torres WE, Colvin RS, et al. Thoracic findings in gastrointestinal pathology. Radiol Clin N Am 1984;22:563-589.
5. Wilson AG. Immunologic diseases of the lungs. In: Armstrong P, Wilson AG, Dee P, Hansell DM. Imaging of diseases of the chest, 2nd ed. St. Louis: Mosby Year Book, 1995:485-567.
6. Shields JB, Joltz S. The retrotracheal space. Radiology 1976;120:19-23.
7. Palayew MJ. The tracheo-esophageal stripe and the posterior tracheal band. Radiology 1979;132:11-13.
8. Lindell Jr. MM, Hill CA, Libshitz HI. Esophageal cancer: radiograph chest findings and their prognostic significance. AJR 1979;133:461-465.
9. Putman CE, Curtis AM, Westfried M, McLoud TC. Thickening of the posterior tracheal stripe: a sign of squamous cell carcinoma of the esophagus. Radiology 1976; 121:533-536.
10. Macpherson RI. Gastrointestinal tract duplications: clinical, pathologic, etiologic and radiologic considerations. RadioGraphics 1993;13:1063-1080.
11. Ishikawa T, Saeki M, Tsukune Y, et al: Detection of paraesophageal varices by plain films. AJR 1985;144:701-704.
12. Tarver RD, Godwin JD, Putman CE. The diaphragm. Radiol Clin N Am 1984;22:615-631.
13. Payne JH, Yellin AE. Traumatic diaphragmatic hernia. Arch Surg 1982;117:18-24.
14. Connell TR, Stephens DH, Carlson HC, Brown ML. Upper abdominal abscess: a continuing and deadly problem. AJR 1980;134:759-765.