The barium swallow, also known as a barium esophagogram or esophagram, is a contrast-enhanced radiographic study commonly used to assess structural characteristics of the entirety of the esophagus. It may be used in the diagnosis of a wide range of pathologies including esophageal motility disorders, strictures, and perforations. It may also be used to characterize more distal issues such as hiatal hernias or gastric volvulus. It may also be used in some capacity to evaluate swallowing at the pharyngeal level, but that is a function that is often served by a Videofluoroscopic Swallow Study.
The barium esophagogram is noninvasive and readily performed, requiring only radiographic still-image capability and contrast medium. As such, it is still a useful exam despite the current wide availability of CT imaging. The use of barium, specifically, barium sulfate, is considered to result in a more sensitive study when compared to those utilizing water-soluble agents such as Gastrografin/diatrizoate.
As with all imaging, interpretation of a barium esophagram requires a knowledge of anatomy and function.
The esophagus is a roughly 20 to 25 cm portion of the gastrointestinal (GI) tract that lies between the oral cavity and stomach. Its role is to transport both solid and liquid oral intake distally to the rest of the GI tract in a coordinated fashion.
The origin of the esophagus is at the level of the cricoid cartilage. This is where the inferior pharyngeal constrictor muscle abuts the cricopharyngeus muscle. This area is known as the upper esophageal sphincter (UES). At the distal end, the esophagus terminates at the lower esophageal sphincter (LES), which is an area of muscular thickening that occurs where the esophagus passes through its diaphragmatic hiatus. When normal anatomy of the LES is disrupted, such as with a hiatal hernia, the sphincter is mechanically defective and can lead to common pathologies such as gastroesophageal reflux.
The UES serves to prevent air from entering the GI tract and prevent reflux of distal GI tract contents into the pharynx. It is located around 15 cm from the incisors. It is composed mainly of the inferior pharyngeal constrictor musculature, specifically the cricopharyngeal portion (also sometimes referenced as the cricopharyngeus muscle). This is notable as it is the most common site of iatrogenic perforation during endoscopy.
The LES, similarly to the UES, plays a critical role in preventing reflux of gastric contents. It is closed at rest but does undergo periodic relaxations from unclear causes and for unclear reasons. As stated earlier, the incompetence of the LES is related to common pathologies such as gastroesophageal reflux disease (GERD) and Barrett metaplasia. The LES is located around 40 cm from the incisors.
In between the esophageal sphincters is the esophageal body. This serves to propel food to the stomach via peristalsis. Although it is functionally a smooth tube, three anatomic landmarks are clinically important and commonly described in the literature as they cause esophageal narrowing. The first is at the UES at the level of the cricoid cartilage. In the mid-portion, the aortic arch and left mainstem bronchus provide some extrinsic compression. The final narrowing is at the LES, which should denote the esophageal hiatus of the diaphragm.
The histologic structure of the esophagus follows the same general schema seen in other muscular GI tract organs. Its wall is composed of several layers including a squamous epithelial mucosa, a muscular layer, and adventitia as its outermost layer. Note that most intraperitoneal portions of the GI tract have serosa as their outermost layer.
Vascular supply of the esophagus is from the inferior thyroid artery in the cervical portion, by the left gastric and inferior phrenic arteries in the abdomen, and via branches from the bronchial arteries and off the aorta otherwise. Venous drainage is via branches to the azygos and hemiazygos veins except distally, where branches drain to the coronary vein. The coronary vein drains into the portal circulation, which is important as these can become varices in the setting of cirrhosis.
Innervation is via the vagus nerve and adjacent sympathetic trunk.
Barium swallow studies are used to define the structure and, to a lesser extent, function. Pathologies typically seen with barium swallow include esophageal perforations, neoplasms, hiatal hernias, and diverticula. Some motility disorders are also readily diagnosed with barium swallow due to the secondary effects they have on esophageal morphology. This includes achalasia, which is characterized famously by a "bird beak" appearance and a dilated, tortuous, proximal esophagus. Diffuse esophageal spasm is identifiable by a "corkscrew" sign.
Another disease that also may benefit from a barium swallow study is that of chemical esophageal injury. In the long term after injury, contrast may be used to identify strictures or sometimes more subtle findings such as ulceration in conjunction with endoscopy. It is important not to obtain contrast studies in the acute setting after chemical esophageal injury.
Further consideration is involved regarding the choice of swallowed contrast agent in the setting of trauma. For the purposes of this section, trauma will be defined as injury resultant from non-iatrogenic causes such as gunshot wounds to the chest. Guidelines for nontraumatic esophageal perforation investigations often involve the use of Gastrografin/diatrizoate (water-soluble) contrast swallow studies initially, followed by a thinned barium swallow study if the study is negative in the face of significant clinical suspicion. This is because barium extravasation into the mediastinum carries a risk of resultant inflammation and is more difficult to wash out than Gastrografin/diatrizoate during surgical exploration. However, a barium contrast study has better sensitivity than that of Gastrografin/diatrizoate in the detection of perforation. In such clinical situations, timeliness of diagnosis is important, and surgical exploration may be likely on a positive swallow study or even already warranted due to other criteria. This would allow for a washout of extravasated contrast, thus minimizing the risks associated with barium while maximizing sensitivity during an urgent workup. Additionally, aspiration of Gastrografin/diatrizoate is known to cause severe pneumonitis. This is of concern in the setting of concomitant tracheal injury that would allow for Gastrografin/diatrizoate to extravasate into the airway. Barium sulfate is not innocuous when aspirated but causes a less severe pneumonitis.
Barium swallow studies should be used in cases of suspected esophageal perforation only after considering the risk of inflammatory mediastinitis. This is not an absolute contraindication and should be weighed against the benefit of obtaining a timely diagnosis. Patients must be capable of swallowing relatively large amounts of contrast without assistance and be able to protect their airway.
Do not administer barium in cases of suspected, acute, chemical esophageal injury. There is little useful information to be gained from a contrast swallow study in those cases.
For studies focused on the pharynx and esophagus, minimal preparation is required. However, patients should be able to tolerate swallowing liquids.
The patient is placed in a prone or supine position with some tilt, essentially a partial lateral decubitus position, to displace the esophagus away from the spine for imaging. One common position is "right anterior oblique" (RAO), where the patient's right side is on the table. Their left arm and knee will be flexed and the head rotated left, allowing for some elevation of the left side. The patient is then asked to rapidly swallow contrast, roughly 100 to 200 cc. The goal, typically, is to distend the esophagus for best resolution. The contrast media may be thinned with water if needed to reveal more subtle lesions. The exact thickness of contrast and amount will depend on the local radiology protocol and also the reason for the exam. Equipment for a still-image X-ray is sufficient in the majority of cases. For certain uses, such as for oropharyngeal dysphagia, fluoroscopy is utilized. Standard posteroanterior and lateral radiographs also may be taken as needed.
If an air-contrast study is desired to further distend the esophagus, effervescent sodium bicarbonate granules may be administered immediately prior to the contrast media.
Oral barium contrast has relatively few adverse effects in standard practice. Most commonly, patients complain of nausea and vomiting within 30 minutes of ingestion. Hypersensitivity reactions have been reported but are uncommon. Most adverse effects are related to extravasation of contrast into the mediastinum or from aspiration.
As stated earlier, the barium esophagram is a quickly performed, readily available study that is useful in the diagnosis and surveillance of a vast range esophageal diseases. In many cases, it is the first and only imaging study that needs to be performed. Additionally, the study may be used to plan surgical intervention by localizing lesions seen in other modalities, such as on endoscopy. The following list of esophageal pathologies (categorized roughly by type) that may benefit from esophagram in workup is not fully inclusive, but it serves to highlight the diversity of clinical situations where it may play some role.
It is important to note that, regardless of the appearance of a lesion discovered on esophagram, all masses, strictures, and complaints of dysphagia require consideration of endoscopy for a complete workup. Additionally, small perforations or fistula may sometimes be detected on endoscopy even with a negative esophagram.