then propels the food bolus down the esophagus and into the stomach [3].
The two muscular rings, the UES and the LES, bookend the top and bottom of the esophagus, respectively. The UES is made of skeletal muscle, is not under voluntary control, and opens following the initiation of a swallow. The LES, or cardiac sphincter, opens to allow passage of food from the esophagus into the stomach and, while closed, helps to prevent the reflux of gastric acidic contents. Dysfunction at the level of the LES due to low basal pressure can cause gastroesophageal reflux, which in turn can produce symptoms of heartburn and regurgitation, and if frequent enough, damage to the underlying esophageal mucosa [4]. Alternatively, elevated LES pressures are seen in motility disorders such as achalasia and often produce symptoms of dysphagia.
Development of esophageal symptoms
The mechanism underlying esophageal pain and discomfort is not well defined, but patient symptoms likely develop as a result of a complex neurophysiologic response to a stimulus on a nociceptor. The esophagus is dually innervated by involuntary parasympathetic (vagal) and sympathetic (spinal afferent) nerves [5]. Vagal nerve cell bodies originate in the medulla. Those within the nucleus ambiguous control skeletal muscle while those within the dorsal motor nucleus control smooth muscle. Efferent nerves from the medulla terminate directly on the motor endplate of upper esophageal skeletal muscle, while efferent nerves directed toward distal esophageal smooth muscle terminate in the myenteric plexus, which is located between the longitudinal and circular muscle layers [6].
Afferent impulses from the esophagus heading toward the spinal cord and brain are typically triggered by the stimulation of a variety of nociceptors within the esophagus. Different chemoreceptors, thermoreceptors, and mechanoreceptors have been identified in the esophageal mucosa, submucosa, and musculature [7]. The sensation of pain is often triggered by chemoreceptor or mechanoreceptor stimulation, as these nociceptors are sensitive to intraluminal distension. Since both vagal and spinal nerves innervate the esophageal mucosa, these afferents are also sensitive to touch, pH, and chemical irritation [5].
The superior laryngeal nerves, recurrent laryngeal nerves, and vagal branches within the esophageal plexus all carry their parasympathetic afferents signals to the vagus nerve, which then carries them on to the brainstem. The splanchnic nerves carry their sympathetic spinal afferent signals to the spinal cord and on to the thalamus [5]. Central perception of symptoms then occurs when these impulses arrive in the brain, either by myelinated fibers that carry pain sensations rapidly and result in sharp, localized pain, or by unmyelinated C‐fibers that transmit impulses more slowly and lead to duller, poorly localized symptoms [8, 9]. These neuroanatomic esophageal pathways are also complex in that they overlap with those of the heart and lungs, as the vagal afferents from all three organs converge prior to their transmission to higher processing centers in the brain. It is for this reason that it can be challenging to discern the anatomic origin of certain symptoms, such as chest pain.
Symptoms
In this section, we will discuss the most common symptoms that are attributed to the esophagus: dysphagia, odynophagia, heartburn, regurgitation, chest pain, globus, and extraesophageal symptoms (Table 1.1).
Table 1.1 Most common symptoms attributed to the esophagus.
| Regurgitation |
| Dysphagia |
| Oropharyngeal (Transfer) |
| Esophageal (Transport) |
| Odynophagia |
| Chest pain |
| Globus |
| Extraesophageal symptoms |
| Chronic cough |
| Change in voice/hoarseness |
| Dental erosions |
| Halitosis |
| Asthma |
| Aspiration |
Dysphagia
The word dysphagia comes from the Greek words phagia (to eat) and dys (with difficulty) and is defined as the sensation of a delay in passage of either a solid or liquid bolus from the mouth to the stomach. Data on the overall epidemiology of dysphagia as a symptom is lacking, and most survey‐based studies vary in their findings. One study from Australia reported the prevalence of dysphagia among adults to be 16% [10], while a more recent study from the United States reported that 3% of both men and women experience at least weekly symptoms [11]. The epidemiology of some specific etiologies of dysphagia has become clearer, with the prevalence of eosinophilic esophagitis found to be higher in young Caucasian men [12, 13].
Dysphagia is an alarm symptom that requires prompt evaluation to determine an etiology and to initiate treatment. It is also a symptom that often causes significant distress to patients and leads them to seek medical attention. There are two types of dysphagia: oropharyngeal (transfer) and esophageal (transport). The most common etiologies of these two types of dysphagia are seen in Tables 1.2 and 1.3, respectively. These two types can often be distinguished by patient history and symptoms.
Patients with oropharyngeal dysphagia often have difficulty initiating a swallow and may have associated symptoms of coughing, choking, aspiration, and gurgling. Drooling, food spillage out of the mouth, and piecemeal swallows are also more strongly suggestive of oropharyngeal dysphagia. Patients sometimes complain of nasopharyngeal regurgitation and the sensation of residual food in the oropharynx. The timing and localization of symptoms are important. Patients with oropharyngeal dysphagia often become symptomatic very shortly after initiating a swallow and often localize the sensation of food sticking to the cervical region [14]. Patients with esophageal dysphagia often complain of food sticking retrosternally in the mid or lower chest. However, some patients with esophageal dysphagia may localize their sensation of food sticking to the cervical region or thoracic inlet, and this feeling can manifest as a referred sensation from a more distal etiology [15, 16]. Most often, dysphagia is not painful, but some patients do complain of a painful fullness or squeezing sensation in the chest. This is different from the pain typically associated with odynophagia, which is usually described as a sharp or severe pain that follows the food bolus during passage down the esophagus.
Table 1.2 Etiologies of oropharyngeal dysphagia.
| AnatomicTumor/MalignancyZenker’s diverticulumCervical osteophyteEnlarged thyroid glandCricopharyngeal barPost‐radiation stricturePharyngeal infection/abscess MuscularMyesthenia gravisPolymyositisMuscular dystrophy NeurologicParkinson’s diseaseMultiple sclerosisCerebrovascular accidentCNS tumorAmyotrophic lateral sclerosis (ALS) |
Table 1.3 Etiologies of esophageal dysphagia.
| Structural/Mechanical | Abnormal Motility |
|
Strictures:PepticRadiationCausticPill‐induced Rings WebsPlummer‐Vinson syndrome Inflammatory conditions:Eosinophilic esophagitisLymphocytic esophagitisLichen planusBullous pemphigoid Esophageal malignancy Benign tumors:Leiomyoma Esophageal diverticula Extrinsic compression:Dysphagia lusoriaMediastinal massOsteophytes
|