Esophagus: The muscular membranous segment between the PHARYNX and the STOMACH in the UPPER GASTROINTESTINAL TRACT.Barrett Esophagus: A condition with damage to the lining of the lower ESOPHAGUS resulting from chronic acid reflux (ESOPHAGITIS, REFLUX). Through the process of metaplasia, the squamous cells are replaced by a columnar epithelium with cells resembling those of the INTESTINE or the salmon-pink mucosa of the STOMACH. Barrett's columnar epithelium is a marker for severe reflux and precursor to ADENOCARCINOMA of the esophagus.Esophageal Neoplasms: Tumors or cancer of the ESOPHAGUS.Esophagoscopy: Endoscopic examination, therapy or surgery of the esophagus.Esophageal Diseases: Pathological processes in the ESOPHAGUS.Esophageal Stenosis: A stricture of the ESOPHAGUS. Most are acquired but can be congenital.Esophagectomy: Excision of part (partial) or all (total) of the esophagus. (Dorland, 28th ed)Esophagogastric Junction: The area covering the terminal portion of ESOPHAGUS and the beginning of STOMACH at the cardiac orifice.Metaplasia: A condition in which there is a change of one adult cell type to another similar adult cell type.Gastroesophageal Reflux: Retrograde flow of gastric juice (GASTRIC ACID) and/or duodenal contents (BILE ACIDS; PANCREATIC JUICE) into the distal ESOPHAGUS, commonly due to incompetence of the LOWER ESOPHAGEAL SPHINCTER.Cardia: That part of the STOMACH close to the opening from ESOPHAGUS into the stomach (cardiac orifice), the ESOPHAGOGASTRIC JUNCTION. The cardia is so named because of its closeness to the HEART. Cardia is characterized by the lack of acid-forming cells (GASTRIC PARIETAL CELLS).Adenocarcinoma: A malignant epithelial tumor with a glandular organization.Esophagoplasty: A plastic operation on the esophagus. (Dorland, 28th ed)Esophagitis: INFLAMMATION, acute or chronic, of the ESOPHAGUS caused by BACTERIA, chemicals, or TRAUMA.Mucous Membrane: An EPITHELIUM with MUCUS-secreting cells, such as GOBLET CELLS. It forms the lining of many body cavities, such as the DIGESTIVE TRACT, the RESPIRATORY TRACT, and the reproductive tract. Mucosa, rich in blood and lymph vessels, comprises an inner epithelium, a middle layer (lamina propria) of loose CONNECTIVE TISSUE, and an outer layer (muscularis mucosae) of SMOOTH MUSCLE CELLS that separates the mucosa from submucosa.Precancerous Conditions: Pathological processes that tend eventually to become malignant. (From Dorland, 27th ed)Esophagitis, Peptic: INFLAMMATION of the ESOPHAGUS that is caused by the reflux of GASTRIC JUICE with contents of the STOMACH and DUODENUM.Esophageal Perforation: An opening or hole in the ESOPHAGUS that is caused by TRAUMA, injury, or pathological process.Peristalsis: A movement, caused by sequential muscle contraction, that pushes the contents of the intestines or other tubular organs in one direction.Manometry: Measurement of the pressure or tension of liquids or gases with a manometer.Esophageal Fistula: Abnormal passage communicating with the ESOPHAGUS. The most common type is TRACHEOESOPHAGEAL FISTULA between the esophagus and the TRACHEA.Carcinoma, Squamous Cell: A carcinoma derived from stratified SQUAMOUS EPITHELIAL CELLS. It may also occur in sites where glandular or columnar epithelium is normally present. (From Stedman, 25th ed)Dimethylnitrosamine: A nitrosamine derivative with alkylating, carcinogenic, and mutagenic properties. It causes serious liver damage and is a hepatocarcinogen in rodents.Esophageal Sphincter, Lower: The physiologic or functional barrier to GASTROESOPHAGEAL REFLUX at the esophagogastric junction. Sphincteric muscles remain tonically contracted during the resting state and form the high-pressure zone separating the lumen of the ESOPHAGUS from that of the STOMACH. (Haubrich et al, Bockus Gastroenterology, 5th ed., pp399, 415)Deglutition: The act of taking solids and liquids into the GASTROINTESTINAL TRACT through the mouth and throat.Endoscopy, Gastrointestinal: Endoscopic examination, therapy or surgery of the gastrointestinal tract.Hypopharynx: The bottom portion of the pharynx situated below the OROPHARYNX and posterior to the LARYNX. The hypopharynx communicates with the larynx through the laryngeal inlet, and is also called laryngopharynx.Hernia, Hiatal: STOMACH herniation located at or near the diaphragmatic opening for the ESOPHAGUS, the esophageal hiatus.Esophageal Achalasia: A motility disorder of the ESOPHAGUS in which the LOWER ESOPHAGEAL SPHINCTER (near the CARDIA) fails to relax resulting in functional obstruction of the esophagus, and DYSPHAGIA. Achalasia is characterized by a grossly contorted and dilated esophagus (megaesophagus).Deglutition Disorders: Difficulty in SWALLOWING which may result from neuromuscular disorder or mechanical obstruction. Dysphagia is classified into two distinct types: oropharyngeal dysphagia due to malfunction of the PHARYNX and UPPER ESOPHAGEAL SPHINCTER; and esophageal dysphagia due to malfunction of the ESOPHAGUS.Endoscopy, Digestive System: Endoscopic examination, therapy or surgery of the digestive tract.Esophagoscopes: Endoscopes for examining the interior of the esophagus.Caustics: Strong alkaline chemicals that destroy soft body tissues resulting in a deep, penetrating type of burn, in contrast to corrosives, that result in a more superficial type of damage via chemical means or inflammation. Caustics are usually hydroxides of light metals. SODIUM HYDROXIDE and potassium hydroxide are the most widely used caustic agents in industry. Medically, they have been used externally to remove diseased or dead tissues and destroy warts and small tumors. The accidental ingestion of products (household and industrial) containing caustic ingredients results in thousands of injuries per year.Stomach: An organ of digestion situated in the left upper quadrant of the abdomen between the termination of the ESOPHAGUS and the beginning of the DUODENUM.Endoscopy: Procedures of applying ENDOSCOPES for disease diagnosis and treatment. Endoscopy involves passing an optical instrument through a small incision in the skin i.e., percutaneous; or through a natural orifice and along natural body pathways such as the digestive tract; and/or through an incision in the wall of a tubular structure or organ, i.e. transluminal, to examine or perform surgery on the interior parts of the body.Fundoplication: Mobilization of the lower end of the esophagus and plication of the fundus of the stomach around it (fundic wrapping) in the treatment of GASTROESOPHAGEAL REFLUX that may be associated with various disorders, such as hiatal hernia. (From Dorland, 28th ed)Esophageal Sphincter, Upper: The structure at the pharyngoesophageal junction consisting chiefly of the CRICOPHARYNGEUS MUSCLE. It normally occludes the lumen of the ESOPHAGUS, except during SWALLOWING.Esophageal Atresia: Congenital abnormality characterized by the lack of full development of the ESOPHAGUS that commonly occurs with TRACHEOESOPHAGEAL FISTULA. Symptoms include excessive SALIVATION; GAGGING; CYANOSIS; and DYSPNEA.Hydrochloric Acid: A strong corrosive acid that is commonly used as a laboratory reagent. It is formed by dissolving hydrogen chloride in water. GASTRIC ACID is the hydrochloric acid component of GASTRIC JUICE.Stomach Neoplasms: Tumors or cancer of the STOMACH.Dilatation: The act of dilating.Diverticulum, Esophageal: Saccular protrusion beyond the wall of the ESOPHAGUS.Foreign Bodies: Inanimate objects that become enclosed in the body.Burns, ChemicalBiopsy: Removal and pathologic examination of specimens in the form of small pieces of tissue from the living body.Duodenogastric Reflux: Retrograde flow of duodenal contents (BILE ACIDS; PANCREATIC JUICE) into the STOMACH.Eosinophilic Esophagitis: Chronic ESOPHAGITIS characterized by esophageal mucosal EOSINOPHILIA. It is diagnosed when an increase in EOSINOPHILS are present over the entire esophagus. The reflux symptoms fail to respond to PROTON PUMP INHIBITORS treatment, unlike in GASTROESOPHAGEAL REFLUX DISEASE. The symptoms are associated with IgE-mediated hypersensitivity to food or inhalant allergens.Upper Gastrointestinal Tract: The segment of GASTROINTESTINAL TRACT that includes the ESOPHAGUS; the STOMACH; and the DUODENUM.Tracheoesophageal Fistula: Abnormal passage between the ESOPHAGUS and the TRACHEA, acquired or congenital, often associated with ESOPHAGEAL ATRESIA.Esophageal Motility Disorders: Disorders affecting the motor function of the UPPER ESOPHAGEAL SPHINCTER; LOWER ESOPHAGEAL SPHINCTER; the ESOPHAGUS body, or a combination of these parts. The failure of the sphincters to maintain a tonic pressure may result in gastric reflux of food and acid into the esophagus (GASTROESOPHAGEAL REFLUX). Other disorders include hypermotility (spastic disorders) and markedly increased amplitude in contraction (nutcracker esophagus).Cineradiography: Motion picture study of successive images appearing on a fluoroscopic screen.Esophageal pH Monitoring: Analysis of the HYDROGEN ION CONCENTRATION in the lumen of the ESOPHAGUS. It is used to record the pattern, frequency, and duration of GASTROESOPHAGEAL REFLUX.Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Bile Reflux: Retrograde bile flow. Reflux of bile can be from the duodenum to the stomach (DUODENOGASTRIC REFLUX); to the esophagus (GASTROESOPHAGEAL REFLUX); or to the PANCREAS.Digestive System Neoplasms: Tumors or cancer of the DIGESTIVE SYSTEM.Gastrointestinal Neoplasms: Tumors or cancer of the GASTROINTESTINAL TRACT, from the MOUTH to the ANAL CANAL.Numismatics: Study of coins, tokens, medals, etc. However, it usually refers to medals pertaining to the history of medicine.Fistula: Abnormal communication most commonly seen between two internal organs, or between an internal organ and the surface of the body.Digestive System: A group of organs stretching from the MOUTH to the ANUS, serving to breakdown foods, assimilate nutrients, and eliminate waste. In humans, the digestive system includes the GASTROINTESTINAL TRACT and the accessory glands (LIVER; BILIARY TRACT; PANCREAS).Anastomosis, Surgical: Surgical union or shunt between ducts, tubes or vessels. It may be end-to-end, end-to-side, side-to-end, or side-to-side.Nitrosamines: A class of compounds that contain a -NH2 and a -NO radical. Many members of this group have carcinogenic and mutagenic properties.Mediastinum: A membrane in the midline of the THORAX of mammals. It separates the lungs between the STERNUM in front and the VERTEBRAL COLUMN behind. It also surrounds the HEART, TRACHEA, ESOPHAGUS, THYMUS, and LYMPH NODES.Retrospective Studies: Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.Laryngopharyngeal Reflux: Back flow of gastric contents to the LARYNGOPHARYNX where it comes in contact with tissues of the upper aerodigestive tract. Laryngopharyngeal reflux is an extraesophageal manifestation of GASTROESOPHAGEAL REFLUX.Larynx: A tubular organ of VOICE production. It is located in the anterior neck, superior to the TRACHEA and inferior to the tongue and HYOID BONE.Disease Progression: The worsening of a disease over time. This concept is most often used for chronic and incurable diseases where the stage of the disease is an important determinant of therapy and prognosis.Risk Factors: An aspect of personal behavior or lifestyle, environmental exposure, or inborn or inherited characteristic, which, on the basis of epidemiologic evidence, is known to be associated with a health-related condition considered important to prevent.Gastroscopy: Endoscopic examination, therapy or surgery of the interior of the stomach.Ulcer: A lesion on the surface of the skin or a mucous surface, produced by the sloughing of inflammatory necrotic tissue.Gastrectomy: Excision of the whole (total gastrectomy) or part (subtotal gastrectomy, partial gastrectomy, gastric resection) of the stomach. (Dorland, 28th ed)Carcinoma, Basosquamous: A skin carcinoma that histologically exhibits both basal and squamous elements. (From Dorland, 27th ed)Case-Control Studies: Studies which start with the identification of persons with a disease of interest and a control (comparison, referent) group without the disease. The relationship of an attribute to the disease is examined by comparing diseased and non-diseased persons with regard to the frequency or levels of the attribute in each group.Duodenum: The shortest and widest portion of the SMALL INTESTINE adjacent to the PYLORUS of the STOMACH. It is named for having the length equal to about the width of 12 fingers.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Gastric Mucosa: Lining of the STOMACH, consisting of an inner EPITHELIUM, a middle LAMINA PROPRIA, and an outer MUSCULARIS MUCOSAE. The surface cells produce MUCUS that protects the stomach from attack by digestive acid and enzymes. When the epithelium invaginates into the LAMINA PROPRIA at various region of the stomach (CARDIA; GASTRIC FUNDUS; and PYLORUS), different tubular gastric glands are formed. These glands consist of cells that secrete mucus, enzymes, HYDROCHLORIC ACID, or hormones.Esophageal Spasm, Diffuse: A hypermotility disorder of the ESOPHAGUS that is characterized by spastic non-peristaltic responses to SWALLOWING; CHEST PAIN; and DYSPHAGIA.Diagnostic Techniques, Digestive System: Methods and procedures for the diagnosis of diseases or dysfunction of the digestive system or its organs or demonstration of their physiological processes.Catheter Ablation: Removal of tissue with electrical current delivered via electrodes positioned at the distal end of a catheter. Energy sources are commonly direct current (DC-shock) or alternating current at radiofrequencies (usually 750 kHz). The technique is used most often to ablate the AV junction and/or accessory pathways in order to interrupt AV conduction and produce AV block in the treatment of various tachyarrhythmias.Epithelium: One or more layers of EPITHELIAL CELLS, supported by the basal lamina, which covers the inner or outer surfaces of the body.Heartburn: Substernal pain or burning sensation, usually associated with regurgitation of gastric juice into the esophagus.Esophagostomy: Surgical formation of an external opening (stoma) into the esophagus.Nodose Ganglion: The inferior (caudal) ganglion of the vagus (10th cranial) nerve. The unipolar nodose ganglion cells are sensory cells with central projections to the medulla and peripheral processes traveling in various branches of the vagus nerve.Pressure: A type of stress exerted uniformly in all directions. Its measure is the force exerted per unit area. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Goblet Cells: A glandular epithelial cell or a unicellular gland. Goblet cells secrete MUCUS. They are scattered in the epithelial linings of many organs, especially the SMALL INTESTINE and the RESPIRATORY TRACT.Photochemotherapy: Therapy using oral or topical photosensitizing agents with subsequent exposure to light.Carcinogens: Substances that increase the risk of NEOPLASMS in humans or animals. Both genotoxic chemicals, which affect DNA directly, and nongenotoxic chemicals, which induce neoplasms by other mechanism, are included.Neoplasm Staging: Methods which attempt to express in replicable terms the extent of the neoplasm in the patient.Esophageal Cyst: Any fluid-filled closed cavity or sac (CYSTS) that is lined by an EPITHELIUM and found in the ESOPHAGUS region.Tumor Markers, Biological: Molecular products metabolized and secreted by neoplastic tissue and characterized biochemically in cells or body fluids. They are indicators of tumor stage and grade as well as useful for monitoring responses to treatment and predicting recurrence. Many chemical groups are represented including hormones, antigens, amino and nucleic acids, enzymes, polyamines, and specific cell membrane proteins and lipids.Mucin-2: A gel-forming mucin found predominantly in SMALL INTESTINE and variety of mucous membrane-containing organs. It provides a protective, lubricating barrier against particles and infectious agents.Pharyngeal Diseases: Pathological processes involving the PHARYNX.