In most cases, the cause is
Progression of an injury to the esophagus
Tumor growth
Injuries that can progress to obstruction can result from damage to the esophagus caused by the repeated backflow of acid from the stomach (gastroesophageal reflux or GERD Gastroesophageal Reflux Disease (GERD) In gastroesophageal reflux disease, stomach contents, including acid and bile, flow backward from the stomach into the esophagus, causing inflammation in the esophagus and pain in the bottom... read more 
), usually over years. Obstruction can also be caused by damage to the esophagus that occurs after swallowing a corrosive substance Caustic Substances Poisoning Caustic substances are highly acidic or alkaline chemicals that can cause severe burns to the mouth and digestive tract when swallowed. When swallowed, caustic substances can burn all tissues... read more (erosive esophagitis) or rarely after inflammation of the esophagus caused by a pill that gets stuck in the esophagus for a period of time.
Tumors are serious causes of narrowing, including cancerous tumors Esophageal Cancer Esophageal cancers develop in the cells that line the wall of the esophagus (the tube that connects the throat to the stomach). Tobacco and alcohol use, human papillomavirus infections, and... read more 
and noncancerous tumors Esophageal Tumors That Are Noncancerous Noncancerous (benign) tumors of the esophagus (the tube that connects the throat to the stomach) are rare. Some tumors can cause problems with swallowing and, rarely, ulcers, bleeding, or both... read more of the esophagus.
Narrowing may also occur when something presses against (compresses) the outside of the esophagus. Compression can result from a number of causes, such as
Enlargement of the left atrium of the heart
An abnormal thyroid gland
A bony outgrowth from the spine
Occasionally, the cause is hereditary (for example, lower esophageal rings Lower Esophageal Ring A lower esophageal ring narrows the lower esophagus and is most likely present at birth. The esophagus is the hollow tube that leads from the throat (pharynx) to the stomach. (See also Overview... read more 
or an esophageal web Esophageal Webs Esophageal webs are thin membranes that grow across the inside of the upper part of the esophagus and may cause difficulty swallowing (dysphagia). (See also Overview of Esophageal Obstructions... read more 
). These disorders usually cause only partial obstruction.
Because all these conditions decrease the diameter of the esophagus, people who have one of them usually have difficulty swallowing Difficulty Swallowing Some people have difficulty swallowing (dysphagia). In dysphagia, foods and/or liquids do not move normally from the throat (pharynx) to the stomach. People feel as though food or liquids become... read more solid foods, particularly meat and bread. Difficulty in swallowing liquids develops much later, if at all.
Diagnosis
Upper endoscopy
Biopsy
Barium swallow x-rays
To diagnose a blockage in the esophagus, doctors do an upper endoscopy. In this procedure, doctors examine the esophagus using a flexible tube called an endoscope Endoscopy Endoscopy is an examination of internal structures using a flexible viewing tube (endoscope). Endoscopy can also be used to treat many disorders because doctors are able to pass instruments... read more . During the endoscopy, doctors take tissue samples to analyze under a microscope (called a biopsy).
Doctors may also do a barium swallow X-Ray Studies of the Digestive Tract X-rays often are used to evaluate digestive problems. Standard x-rays (plain x-rays) do not require any special preparation (see Plain X-Rays). These x-rays usually can show a blockage or paralysis... read more . In this test, people are given barium in a liquid before x-rays are taken. The barium outlines the esophagus, making abnormalities easier to see.
Treatment and outcome depend on the cause of the narrowing or blockage.
