There are two types of symptoms in acid reflux disease: esophageal and extra-esophageal (also called typical and atypical). We all know about heartburn the typical symptom of acid reflux, which is initiated by the direct injurious effect of acid upon the esophageal lining. Heartburn has been linked to the esophageal entity because it represents a characteristic subjective sensation resulting specifically from esophageal irritation.
So, what about extra-esophageal symptoms?
The term extra-esophageal sounds anatomically; meaning sites other than the esophagus.
Extra-esophageal sites include the larynx, the trachea, the bronchi and both lungs.
The pharynx is a common compartment, at which portals of entry into the esophageal tube and the respiratory tract are located.
At the junction between the esophagus and the pharynx there is a sphincter, the upper esophageal sphincter which opens only during swallowing to allow ingested food pass from the mouth into esophagus. That means it's contracted most of the time and by this function it serves two important actions, first it prevents swallowing of air in one direction and second prevents the incidentally refluxed acid from entering the pharynx in the other direction.
Whenever a disturbance in this activity is encountered due to a motility disorder for example; acid being refluxed into the pharynx, would be aspirated into the larynx.
The effects of pharyngeal irritation are usually experienced as sore throat. The situation is quite different in case of laryngeal irritation because the surface lining of the larynx is very sensitive. Such a characteristic feature of the larynx is meant to protect the respiratory tract from the inhalation of any foreign material. The immediate response is severe cough to expel any aspirated substance. This cough mechanism as a line of defense is endorsed by the contraction of the upper esophageal sphincter on one hand and the esophageal acid clearance mechanisms on the other hand. Repeated exposure of the larynx to chemical irritation associated with acid reflux results in inflammation of the larynx (laryngitis) with symptoms as hoarseness of voice, vocal fatigue and voice breaks. These direct effects would also be encountered when the trachea and bronchi are affected with similar inflammatory changes as they are in continuity with the larynx and are usually complained of as chronic cough. Sometimes the reflux is aspirated in small amounts into the lung (micro-aspirations) and is complicated with inflammation (pneumonia) which may progress to lung fibrosis. These serious complications usually cause difficulty in breathing (dyspnea).
That is all about how acid reflux causes extra-esophageal symptoms by a direct effect upon the respiratory tract, and as we have noticed is associated with evidence of direct chemical irritation in the form of inflammation. That does not conclude the effects as some well known extra-esophageal presentations such as bronchial spasm is not associated with any organic changes; neither irritation nor inflammation?.
Well, that is the other side of the story; acid reflux causes extra-esophageal symptoms by reflex actions. A reflex action is an automatic (involuntary) neuromuscular action elicited by a defined stimulus. To simplify, a reflex action includes: a receptor; a specialized sense organ located in a surface and an effector; muscle fibers located in a wall which automatically respond to an electric impulse generated by stimulation of the receptor and transmitted through nerve fibers to the effector's site. For example, a person stepping on a sharp object would initiate the reflex action through the creation of a stimulus, within receptors located in the skin tissue of the foot. The resulting stimulus would be transmitted through sensory neurons to the spinal cord. This stimulus is usually processed to create an immediate response by initiating a muscular response which is acted upon by muscles of the leg, retracting the foot away from the object. In our case the acid replaces the sharp object (stimulus), the esophageal surface lining replaces the skin tissue of the foot (receptor) and muscle fibers in the wall of the bronchi instead of muscles of the leg (effector). Accordingly asthma like symptoms in the form of wheezing and difficulty in breathing are scenarios of broncho-constriction, a reflex action induced by acid reflux.
Anatomically related sites which show other manifestations of reflux include: para-nasal sinuses and the middle ear, both of them are communicating with the pharynx either directly or indirectly. The effects are mostly related to direct irritation followed by inflammation in the form of sinusitis and otitis media respectively.
Dental changes are due to enamel erosion and a bad breath is a reflection of infection on top of upper respiratory tract inflammation.
Inflammatory changes just enumerated may also be complicated by ulcers, polyps or even cancer and these implicate frequent endoscopies.
Another fact is that acid reflux may present only with these extra-esophageal symptoms without the classical heartburn.
A therapeutic trial of proton pump inhibitors should be attempted twice daily and if no relief within 4-6 weeks acid monitoring should be considered along with the treatment.
Frequent aspirations and recurrent lung inflammations are indications for surgery.
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