Diagnostic Imaging of the Pharynx and Esophagus

CHAPTER 102 Diagnostic Imaging of the Pharynx and Esophagus

As the diversity of radiologic examinations continues to grow, it is increasingly important for referring clinicians to understand the arsenal of tests offered by radiologists. The improved quality and availability of cross-sectional imaging, along with advances in endoscopic techniques, have contributed to a decline in fluoroscopy. However, many disorders of the pharynx and esophagus still are best evaluated with fluoroscopic techniques. In particular, patients who have pain, trismus, a hyperactive gag reflex, or bulky disease are often not optimally evaluated with direct inspection or endoscopy, and mucosal lesions may not be evident on cross-sectional modalities. This chapter discusses the basics of radiographic technique and anatomy, with a focus on the appropriate choice of imaging modality for evaluation of the pharynx and esophagus. The radiographic appearance of specific disorders is then discussed.


Conventional Radiography

Conventional radiographs (plain films) of the neck are economical and readily available. They are particularly useful in pediatric patients with airway distress. The lateral projection provides the most information, and it will often be obtained without the frontal projection (Fig. 102-1). If the examination is performed to evaluate a radiopaque foreign body, the frontal projection should be included. Patients are instructed to say the letter “e” during exposure to bring the tongue forward and better demonstrate the oropharynx.1 If a hypopharyngeal lesion is being evaluated, the patient should blow through compressed lips to distend the hypopharynx. In children, the lateral radiograph should be obtained during peak inspiration to prevent redundancy of the prevertebral soft tissues that may simulate pathology.

Chest radiographs occasionally reveal advanced esophageal abnormalities or pneumomediastinum, but fluoroscopy and cross-sectional imaging are preferred for evaluation of the thoracic esophagus.

Computed radiography and digital radiography are the modern counterparts to screen-film techniques. Instead of exposing a piece of film, the technologist captures an image on a reusable array of digital elements and reads the image directly into a computer. One advantage of these techniques is the ability to emphasize subtle soft tissue differences, even in suboptimally exposed images.2

Xeroradiography is a historical technique that clearly delineated the soft tissues of the neck.3 However, xeroradiography had a narrow range of applications, and it is no longer available at most institutions.

Linear and complex-motion tomography improve on conventional radiographs by blurring the soft tissues that obscure the pharyngeal walls. Small mucosal lesions can sometimes be distinguished, but conventional tomography has been replaced almost universally by computed tomography (CT).


Motion capture techniques with intraluminal contrast are invaluable when studying the functional dynamics of the pharynx and esophagus. Although endoscopy provides direct visualization of the mucosa, radiographic techniques provide a more physiologic examination. Both cineradiography (high-resolution images obtained at a low frame rate) and video capture (low-resolution images obtained at a high frame rate) are used in each examination. Cineradiography provides better spatial resolution for mucosal detail, whereas video capture allows more dynamic evaluation with less radiation. At most institutions, the video capture is not permanently stored, so it may be cumbersome or impossible to review these data after the examination is completed.

On traditional film, radiodense elements appear whiter than radiolucent elements. This convention has not persisted in the age of digital imaging; some aspects of anatomy and pathology are visualized better when the image is inverted. The images in this chapter follow the traditional convention.

The term “esophagram” is slowly replacing the ambiguous term “barium swallow.” Note that an esophagram, which is designed to evaluate the pharyngeal and esophageal mucosa, is distinct from a “modified barium swallow,” which evaluates laryngotracheal aspiration and is usually performed in conjunction with a speech pathologist. At some institutions, an esophagram includes a complete evaluation of the pharynx, but at other institutions, a “cervical esophagram,” “pharyngoesophagram,” or “pharyngography” must be specifically requested. Note that the nasopharynx is not evaluated with fluoroscopic techniques; cross-sectional imaging is required.


A complete esophagram has three phases: full-column (single contrast), air-contrast (double contrast), and mucosal relief.4 To obtain full-column images, the patient is given a thin suspension of barium by mouth. The pharynx is best imaged in the standing position, with rapid cineradiography (four to six images per second) in several projections (Fig. 102-2). In the frontal projection, the patient’s neck is extended to prevent the jaw from obscuring the pharynx. When digitally displayed, cine images reveal much of the swallowing dynamics. Video capture is still useful, however, to evaluate equivocal filling defects.

Full-column images of the esophagus (Fig. 102-3) are obtained in a prone oblique position, with the patient drinking barium suspension from a straw. There are two objectives to this portion of the examination: evaluate esophageal peristalsis and maximally dilate the esophagus to identify contour abnormalities. Peristalsis is evaluated with videotaped single swallows. Maximum dilatation is achieved with rapid swallows followed by a Valsalva maneuver. The prone position eliminates gravity as a factor in peristalsis.

Air-contrast images of the esophagus (see Fig. 102-3) are obtained with the patient upright and in slightly left anterior obliquity. An effervescent agent is first administered, followed by a thick barium suspension. The barium coats the mucosal surface, whereas the gas from the effervescent agent distends the lumen. This provides exquisite mucosal detail and is most useful for the evaluation of small plaquelike mucosal tumors and the mucosal irregularities of esophagitis.5 If the patient is unable to undergo the air-contrast portion of the thoracic esophagram, prone full-column imaging should be obtained in two orthogonal planes as an alternative.

Air-contrast images of the pharynx are not always necessary because this region is amenable to direct inspection. However, in some cases, such as tumors arising in the hypopharynx, air-contrast images are of use. After the administration of thick barium suspension, phonation and a modified Valsalva maneuver are used to distend the pharynx (Fig. 102-4).

Mucosal-relief images of the esophagus (Fig. 102-5) are obtained after the administration of thick barium suspension, but without air distention. Esophageal varices and some mucosal lesions are best seen with mucosal relief. Only the distal esophagus and gastroesophageal junction need to be imaged in this phase of the examination.

At the conclusion of an esophagram, after the esophagus has completely cleared all contrast, Valsalva and modified Valsalva maneuvers should be performed to document gastroesophageal reflux. It is important to realize, however, that these maneuvers are insensitive for the diagnosis of intermittent gastroesophageal reflux.

Oral Contrast Agents

Barium suspension is the best-known fluoroscopic contrast agent, but some patients are not appropriate candidates for oral barium administration. Patients who may have a perforated pharynx or esophagus are at risk for barium extravasation into the soft tissues of the neck or chest. Extravasated barium may incite an inflammatory reaction or may become inspissated and fail to resorb.8 Water-soluble contrast agents (such as those used for intravenous CT contrast) may be used as an alternative. Unfortunately, water-soluble agents are not as dense as the barium suspension, so they are less sensitive to small leaks. If no leak is detected after the administration of a water-soluble agent, the examination should be repeated with barium.9

Ionic contrast agents have another disadvantage: if they are aspirated into the lungs, they may cause a chemical pneumonitis and pulmonary edema.10 Nonionic water-soluble agents are presumed to be safer and thus should be used if there is a risk of aspiration or tracheoesophageal fistula.

Oil-based contrast agents for the evaluation of the larynx and pharynx are of historical interest only.

Computed Tomography

At most institutions, CT is the modality of choice for evaluating masses in the neck and chest. Two recent advances have dramatically changed the quality of CT imaging: multidetector scanners and helical acquisition. Multidetector scanners have several rows of photoreceptors, allowing the simultaneous acquisition of several slices. Helical techniques allow patients to move continuously through the scanner instead of stopping for each slice. These advances have dramatically decreased scan times and radiation doses while improving spatial resolution.11 This improved resolution allows multiplanar and three-dimensional reconstructions that rival magnetic resonance (MR) for clarity and diagnostic accuracy. The rapid scan times permit dynamic CT imaging, which can assess vascularity and other physiologic properties.12

CT is readily available and provides critical information about the extent and character of mass lesions. In known tumors, CT is used to determine the degree of invasion into surrounding deep tissues, the relationship of the neoplasm to critical structures such as the vocal cords and arteries, and the involvement of regional lymph nodes.13 CT is comparable to magnetic resonance imaging (MRI) for the evaluation of bone invasion,14 but MRI is preferred for the evaluation of soft tissue extent, particularly at the skull base.15 Disadvantages of CT include artifacts from dental amalgam and from patient body habitus, particularly at the shoulders.

Intravenous contrast is of particular importance in the neck because enlarged lymph nodes may be difficult to distinguish from unenhanced vessels. Allergies to contrast material and renal dysfunction are relative contraindications to intravenous contrast. Some practitioners avoid intravenous contrast in patients who may require radioablation of thyroid neoplasms because the contrast can impede iodine uptake for an indeterminate amount of time after the examination.

Ionic contrast media are more prone to allergic reactions than the more expensive nonionic media. For this reason, some institutions have abandoned ionic contrast media. Ionic contrast should be avoided in patients with airway pathology because a mild allergic reaction could precipitate severe airway compromise.

Helical neck CT should be performed with a maximum slice thickness of 3 mm. Thinner slices may be required to delineate the extent of pathology, particularly in tumors near the larynx. A contrast bolus of 75 to 125 mL is used, with a delay of 30 to 60 seconds.16 Faster scanners require longer contrast delays, so revised protocols are required when equipment is upgraded. CT of the chest is performed with a thickness of 5 to 7 mm; additional intravenous contrast is usually not required. CT of the neck and chest should not be performed as a continuous acquisition because the arms are positioned differently for the two scans.

Magnetic Resonance Imaging

Unlike CT, which relies on ionizing radiation to create images, MRI uses a strong magnetic field and radiofrequency pulses to interrogate the patient’s tissues. It is particularly useful for evaluating tumors of the pharynx and larynx, but it is less useful in the thorax, where motion artifact and field distortions prevent a thorough evaluation of the mediastinum.17

MRI has the substantial advantage of multiple pulse sequences, which allows more precise characterization of pathologic tissue. The most frequently used sequences are T1-weighted and T2-weighted sequences. Postcontrast images are exclusively T1 weighted. T1-weighted images demonstrate anatomic relationships, whereas T2-weighted images are sensitive for pathology. Many additional sequences and modifications (e.g., inversion recovery, fat suppression, magnetization transfer, and diffusion weighting) can more precisely determine tissue characteristics and extent of pathology.

Advantages of MRI include reduced artifacts from dental amalgam and body habitus, as well as the ability to directly image in any plane including oblique planes. The gadolinium-based intravenous contrast agents used in MRI have a substantially lower risk of allergic reaction than CT agents do.18 Disadvantages of MRI include the long duration of MRI studies, which sometimes results in motion artifact, especially in debilitated patients or patients with respiratory compromise. The small bore of the MRI magnet often induces claustrophobia. Many patients cannot go near the MRI magnet because of metallic or electronic implants that might be displaced or triggered by the rapid changes in the magnetic field.19 In particular, cardiac pacemakers/defibrillators, cochlear implants, and ferromagnetic aneurysm clips are relative contraindications to MRI.20 Metallic foreign bodies may also be of concern, depending on their location.21

Different receiving coils are available for MRI, with characteristics tailored to different body parts. It is critical for head and neck patients to be imaged with a surface coil, which allows for improved spatial resolution and higher signal-to-noise ratios. Low-field “open” MRI magnets do not have the spatial resolution or signal-to-noise characteristics to evaluate the intricate anatomy of the skull base or larynx and are not recommended for imaging of the head and neck.


Transcutaneous sonographic evaluation of the neck22 has undergone a resurgence in popularity in patients with thyroid cancer and for guidance in interventional procedures. Although ultrasound can be used to evaluate superficial lymph nodes in the neck, it may overlook deep nodes and cannot be relied on for a complete evaluation of cervical tissues. Transesophageal echosonography provides information that is complimentary to CT and invaluable for the evaluation of the extent of esophageal lesions across tissue planes.23 All sonographic techniques are highly operator dependent, so experienced technologists and appropriately trained physicians are necessary to produce diagnostic-quality examinations.

Positron Emission Tomography-Computed Tomography

Combined 18F-fluorodeoxyglucose positron emission tomography and CT scanning (PET/CT) has revolutionized the care of head and neck cancer patients.24 PET is a functional imaging technique that relies on the increased metabolic uptake of glucose in tumors to identify unknown primary tumors, stage malignancies, search for metastatic disease, and evaluate recurrences.25,26 The major limitation of PET imaging is its poor spatial resolution, which is particularly significant in the head and neck. Combined PET/CT scanners use the high spatial resolution of CT with the functional information of PET to produce fused images that overcome this difficulty (Fig. 102-6). For the evaluation of head and neck cancers, PET/CT is superior to either PET or CT alone.27

PET/CT is used in the staging of cancer, the monitoring of treatment response, and the surveillance of treated patients.28 Optimal monitoring and surveillance schemata have not yet been established, but it is known that PET/CT should not be performed until at least 8 weeks after the conclusion of therapy to avoid both false-positive and false-negative results.29 Surveillance with PET/CT is particularly useful because of the low rate of false-negative studies.

The analysis of PET/CT scans is complicated and requires a radiologist with experience in both PET/CT and head and neck imaging. Physiologic uptake of FDG is prevalent in the head and neck, especially during contraction of muscles (e.g., neck and thyroarytenoid muscles), and may therefore be confused with tumor uptake.30 Inflammation, either postoperative or from infectious sources such as the teeth, palatine, or lingual tonsils, may also obscure the interpretation, resulting in false-positive reads and unnecessary clinic evaluations and biopsies.

Future trends in PET/CT will likely include combined PET-MR scanners, the development of novel ligands to supplement or replace fluorodeoxyglucose, and guidance for optimizing the utilization of this relatively new modality.

Other Nuclear Medicine

Although PET/CT is the most commonly used nuclear medicine examination in the head and neck, other nuclear medicine tests are sometimes of use. Esophageal transit, gastroesophageal reflux, and gastric emptying can be studied with conventional nuclear medicine techniques.31,32 These studies are more sensitive than fluoroscopy for the presence of reflux, but the quantitative degree of reflux does not correlate well with symptoms. Radionuclide swallowing studies are used predominantly in the pediatric population.

Radiographic Anatomy


The radiographic anatomy of the pharyngeal lumen is best visualized with air-contrast fluoroscopic images (see Fig. 102-4). The mucosal surfaces of the epiglottis, vallecula, and pyriform sinuses are easily identified. Normal asymmetry of the lingual tonsils should not be confused with a vallecular mass. The epiglottis is best evaluated in the lateral projection, where its thickness can be directly assessed. The pyriform sinuses may be asymmetric, but a complete lack of filling is suspicious for tumor. Barium pooled between the posterior margin of the larynx and the posterior wall of the hypopharynx forms the postcricoid line (see Fig. 102-4). Disruption or irregularity of this line is a sign of tumor invasion. The cricopharyngeus muscle lies anterior to the sixth cervical vertebra. It may be seen as a slight indentation on the posterior wall of the hypopharynx, but it is often not visualized in normal individuals. The normal cross-sectional anatomy of the upper aerodigestive tract is demonstrated in Figures 102-7 and 102-8.33


The esophagus begins at the level of the sixth cervical vertebra. The cervical esophagus lies posterior to, and slightly to the left of, the trachea (see Fig. 102-7). Surrounding structures that may affect the cervical esophagus include the trachea, cervical spine, thyroid and parathyroid gland, and cervical lymph nodes. On CT, the anteroposterior diameter of the collapsed cervical esophagus should not exceed 16 mm, and its lateral dimension should not exceed 24 mm, except at the esophageal verge, where it may be more prominent.34 On full-column lateral projections, there is a normal mucosal irregularity of the anterior esophagus just below the cricoid cartilage (see Fig. 102-2). This is caused by lax mucosal folds overlying the ventral submucosal venous plexus, and it should not be mistaken for tumor invasion or a web.35 Unlike webs and tumors, the venous plexus changes shape during swallowing.

The thoracic esophagus lies anterior to the spine, anteromedial to the descending aorta (see Fig. 102-7). The phrenic ampulla, which is a normal widening of the esophageal lumen, is seen just above the gastroesophageal junction (Fig. 102-9). There are three normal indentations on the anterolateral esophagus: aortic arch, left mainstem bronchus, and left atrium (see Fig. 102-3). Other nearby structures include the descending aorta, aortic arch and great vessels, carina, mediastinal lymph nodes, and spine.

When the esophagus is filled with contrast, it is a featureless tube. When the esophagus is collapsed, longitudinal mucosal folds appear along the entire length of the organ. Occasional transverse folds are normal.

Motility Disorders


The modified barium swallow is the most appropriate radiologic test to evaluate swallowing dysfunction.7 Although an esophagram provides some information about deglutition, the modified swallow uses barium of several different consistencies, which provides a more detailed evaluation. Functional endoscopic evaluation of swallowing, with or without sensory testing, has been proposed as an alternative to the modified swallow.36 However, the modified swallow provides a more physiologic environment because there is no endoscope to interfere with motility. During a modified swallow, patients can use protective maneuvers such as chin tuck and forced cough, which are not available during endoscopy. Furthermore, the modified swallow evaluates the upper phases of swallowing in more detail.37 Endoscopy and modified swallow are considered complementary examinations at most institutions.

The modified barium swallow can evaluate all phases of the swallow reflex.1,6,38 The tongue forms the oral bolus and then transports it from the oral cavity to the oropharynx. The soft palate elevates and approximates the posterior pharynx to prevent velopharyngeal reflux. The entire larynx elevates, followed by a peristaltic wave through the pharynx. The epiglottis inverts to deflect the bolus into the pyriform sinuses and protect the laryngeal vestibule. At the bottom of the hypopharynx, the cricopharyngeus muscle relaxes to permit the passage of the food bolus.

Velopharyngeal occlusion can be observed directly. Elevation of the larynx is best visualized by observing the hyoid bone. Epiglottic inversion is fast, and confirmation of this event may require review of the video images. Brief episodes of contrast penetration may be seen in the laryngeal vestibule. If the contrast clears rapidly and without cough, this finding does not indicate a risk of tracheal aspiration. A small amount of barium may pool in the valleculae or the pyriform sinuses in normal patients, but the peristaltic wave should strip the contrast from the remainder of the pharynx. The cricopharyngeus muscle lies at the level of the C6 vertebral body, and it is not normally visualized.

Abnormal Deglutition

Aspiration can occur in any phase of deglutition. During the oral phase, incomplete control of the oral bolus allows contrast to spill over the base of the tongue into the vallecula. In severe cases, the vallecula will fill completely, and contrast will spill over the epiglottis into the larynx. During peristalsis, failure of epiglottic inversion allows contrast to enter the larynx. After the swallow, incomplete clearance of contrast leads to postprandial aspiration when the patient resumes breathing.

Abnormal pharyngeal motility is caused by disorders of the brainstem, cranial nerves IX and X, the myoneural junction, or the pharyngeal musculature. Myasthenia gravis is a disorder of the myoneural junction that produces hesitancy in swallow initiation, nasopharyngeal reflux, enlargement of the pharynx, tracheal aspiration, and incomplete clearance. The findings worsen over consecutive swallows and improve after neostigmine administration. Diseases that affect the pharyngeal muscles such as dermatomyositis, systemic lupus erythematosus, myotonic dystrophy, systemic sclerosis, and oculopharyngeal myopathy produce weakened pharyngeal contractility with incomplete clearance.

Unilateral pharyngeal palsy causes an asymmetry in the pyriform sinuses because the contrast is thrown to the palsied side by the functioning pharyngeal constrictors.39 This asymmetry should not be misinterpreted as a filling defect from carcinoma in the unaffected side. A careful dynamic examination of several swallows may be necessary to prevent this diagnostic error.

Cricopharyngeal Dysfunction

Unlike the other muscles of pharyngeal constriction, the cricopharyngeus remains contracted between swallows, acting as an upper esophageal sphincter. It normally relaxes during deglutition to allow the passage of the food bolus. When the muscle fails to completely relax (cricopharyngeal achalasia), there is a smooth posterior impression on the hypopharynx at the level of the C6 vertebra (Fig. 102-10). Unlike most retropharyngeal masses, the cricopharyngeus does not exceed 1 cm in vertical dimension. The most frequent cause of cricopharyngeal achalasia is cerebrovascular disease. Other causes include pseudobulbar palsy, nasopharyngeal carcinoma, poliomyelitis, thyroid myopathy, cervical vagotomy, polymyositis, dermatomyositis, oculopharyngeal syndrome, amyotrophic lateral sclerosis, and hiatus hernia, but many cases are idiopathic. Cricopharyngeal achalasia has been implicated in the development of Zenker’s diverticula.40

Incompetence of the upper esophageal sphincter is called cricopharyngeal chalasia. It manifests radiographically as a lack of cricopharyngeal impression between swallows. Cricopharyngeal chalasia is specific for myotonic dystrophy, although most patients with myotonic dystrophy have cricopharyngeal achalasia instead.41

Delayed opening of the cricopharyngeus, seen in familial dysautonomia, results in aspiration and recurrent pulmonary infections. This disorder is distinct from cricopharyngeal achalasia in that the muscle relaxes completely after a delay.


Manometry is considered the reference standard for evaluation of esophageal dysmotility. The relative sensitivity of fluoroscopy, radionuclide scans, and manometry is controversial.31,32,42,43 However, radiographic techniques are less invasive and elicit less patient discomfort. Fluoroscopy has the additional advantage of identifying structural abnormalities.

A normal (primary) peristaltic wave is initiated by a swallow. The wave passes uninterrupted to the lower esophageal sphincter (LES). The contrast bolus should remain intact during a primary wave; contrast that escapes proximally is the earliest sign of weakened peristalsis. Secondary peristaltic waves are initiated in the midesophagus by local irritation such as from gastroesophageal reflux or retained food. Tertiary contractions are nonperistaltic local contractions, a contributing factor in dysmotility.

Diminished Peristalsis

Achalasia is a neuromuscular disorder caused by degeneration of Auerbach’s plexus.44 Peristalsis fails, but the LES remains tight, so the esophagus progressively dilates. In severe cases a dilated esophagus with retained food can be appreciated on a chest film. On fluoroscopy, the distal esophagus has a conical (beaked) shape (Fig. 102-11). In early stages of the disease, the esophagus may be only minimally dilated, with dominant tertiary contractions. This is called vigorous achalasia, and it may mimic esophageal spasm (Fig. 102-12).45 Patients with achalasia are at increased risk of esophageal carcinoma, and radiographic screening may be indicated.46,47

Impairment of the LES is a constant feature of achalasia, but it is not pathognomonic. Patients with diffuse esophageal spasm, presbyesophagus, or connective tissue diseases may also have impaired relaxation of the LES. Carcinoma of the distal esophagus or gastric cardia can mimic achalasia.48 Chagas’ disease, in which the parasite Trypanosoma cruzi affects the ganglion cells of the esophagus, may appear identical to achalasia on an esophagram.49 Other mimics of achalasia include central and peripheral neuropathies such as stroke, diabetes mellitus, and amyloidosis, and strictures from reflux esophagitis.40

Presbyesophagus is a failure of peristalsis associated with aging. It is frequently observed in older patients with dysphagia, but the relationships among reflux esophagitis, presbyesophagus, and dysphagia remain unclear.50 Presbyesophagus manifests as failure of the primary peristaltic wave with intermittent tertiary contractions.

Many other diseases can cause diminished peristalsis including severe esophagitis, diabetes, alcoholism, hyperthyroidism, anticholinergic medications, and surgical vagotomy.40


Jun 5, 2016 | Posted by in OTOLARYNGOLOGY | Comments Off on Diagnostic Imaging of the Pharynx and Esophagus
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