Odynophagia overview

# Overview
Odynophagia is defined as painful swallowing. It is caused by various medical conditions. It should not be confused with dysphagia, which is difficulty in swallowing. Common causes of odynophagia are throat infections, foreign body, acid reflux disease, tumors, or injuries which may lead to difficulty in swallowing due to disturbing pain. Odynphagia is a word with Greek origin. There is no established system for the classification of odynophagia. However we can classify them according to causes to approach the area of involvement. The pain in swallowing is induced due to conditions causing stimulation of sensory nerves innervating esophagus and pharynx. Several diseases, such as, Achalasia cardia, Esophageal cancer, Myasthenia gravis, Scleroderma, Tonsillitis, upper respiratory tract infections, Zenkers diverticulum and gastroesophageal reflux disease have odynophagia as one of their presenting symptoms and thus, it is essential to differentiate these diseases from one another.

# Historical Perspective
Odynophagia is a Greek word. (/o-dn-fej-ji-/; from odyno- "pain" and phago "to eat") is pain when swallowing. Other than that there is no specific historical background of odynophagia.

# Classification
There is no established system for the classification of odynophagia. However we can classify them according to causes to approach the area of involvement. Odynophagia may be classified according to causes into two groups which include disorders of esophagus and disorders of pharynx.

# Pathophysiology
The pain in swallowing is induced due to conditions causing stimulation of sensory nerves innervating esophagus and pharynx. Infections of esophagus or pharynx cause fluid to leak into the interstitial media of mucous epithelium and it produce pressure on sensory nerve terminals situated in the mucosa. Tumors produce pain due to compression effect of mass on sensory nerve terminals situated in mucosa. Foreign body produce pain due to compression effect of foreign body on sensory nerve terminals situated in mucosa.

# Causes
There are several diseases that present with odynophagia. Some of them include Achalasia cardia, Esophageal cancer, Myasthenia gravis, Scleroderma,Tonsillitis, Upper respiratory tract infections, Zenkers diverticulum and Gastroesophageal reflux disease.

# Differentiating Odynophagia from other Conditions
The causes of odynophagia are of various pathologies. Differentiating them with adjacent history and examination is helpful to narrow down the exact pathology.

# Epidemiology and Demographics
Common causes of odynophagia have their independent statistics. In 2015, In the USA, the prevalence of pharyngitis was 4.8 per 100,000 people with group A strep. The prevalence of GERD In the USA and Europe ranges from low of 10,000 per 100,000 persons to high of 20,000 per 100,000 people. In Asia, the prevalence of GERD is 5,000 per 100,000 people. The prevalence of esophagitis In the USA and Europe ranges from low of 10,000 per 100,000 persons to high of 20,000 per 100,000 people. In Asia, the prevalence of esophagitis is 5,000 per 100,000 people.

# Risk factors
Risk factors depend on the individual risk factors of disease causing odynophagia.

# Natural history, complications and prognosis
The causes of odynophagia have their own independent course of progression and complication. However if disease is treated then pain is also relived to a certain degree depending on what the cause is.

# History and Symptoms
Odynophagia is a symptom. History of patient presenting with painful swallowing will help in narrowing down the cause of odynophagia. The cornerstone of any dysphagia evaluation is a detailed history, and a thorough review of symptoms that can differentiate esophageal from oropharyngeal odynophagia and help predict the specific etiology of odynophagia. How a patient describes his or her difficulty and its timing, associated symptoms, and other characterizations may specifically denote the anatomic level of swallowing dysfunction.

# Physical examination
Physical examination of patients with odynophagia is dependent on the underlying cause. Patients with odynophagia usually appear in discomfort. May be feverish and tachycardic in case of inflammation. May have exanthem in case of viremia or bacteremia. Neuromuscular examination of patients with odynophagia is usually normal. However in cases of URTI causing meningitis may produce symptoms of meningeal irritation.

# Laboratory Findings
Common tests which should be ordered in every case are CBC, ESR/CRP and some specific tests depending on the underlying etiology.

# Electrocardiogram
An electrocardiogram can be used to assess for left atrial enlargement or in viral infections also causing pericarditis. It may also be used to differentiate the cause of esophageal spasm.

# Chest x ray
The use of radiography of chest may help in differentiating multiple causes of odynophagia in the chest.

# CT
The benefit of using CT over X-ray is that it delineates the causative agent of odynophagia with more accuracy as compared to x-ray.

# MRI
An MRI of the brain can be used to exclude CVA and mass lesions of the head and neck. It is more helpful in soft tissue margins which are causing pain in swallowing.

# Echocardiography or ultrasound
Echocardiography can be used to rule out cardiac causes of odynophagia.

# Medical therapy
The treatment of odynophagia depends on identifying and treating the underlying primary etiology. However some of the cases obtain benefit of using soothing agents as marshmallow plant, Sage and echinacea, apple cider vinegar, salt water gargle, honey, Licorice root, lemon water, ginger root tea, coconut oil, cinnamon, plenty of fluids, chicken soup, peppermint tea, chamomile tea and herbal throat lozenges.

# Surgery
Conditions causing pain on swallowing such as tumors, chronic inflammation inducing stricture, neuropathies not responding to medications or rings may need surgery to relive narrowing. As narrowing is resolved then food passage is smooth and pain is relived. Most of the conditions not responding to medication benefits with balloon dilation are treated surgically.

# Primary Prevention
Odynophagia can be prevented primarily by avoiding the conditions causing it. Earlier diagnosis of tumors and treatment of conditions causing inflammation of upper respiratory tract or upper GI tract will reduce the chances of development of odynophgia.

# Secondary prevention
The conditions causing odynophaiga are treatable. Once the pathology causing odynophaiga are treated then pain on swallowing also improves. However soothing agents help in faster recovery when primary cause is addressed.