The increased incidence of Crohn's in the industrialized world indicates an environmental component. Crohn's is associated with an increased intake of animal protein, milk protein and an increased ratio of omega-6 to omega-3 polyunsaturated fatty acids.

Those who consume vegetable proteins appear to have a lower incidence of Crohn's disease. Consumption of fish protein has no association.

Smoking increases the risk of the return of active disease (flares). The introduction of hormonal contraception in the United States in the 1960s is associated with a dramatic increase in incidence, and one hypothesis is that these drugs work on the digestive system in ways similar to smoking. Isotretinoin is associated with Crohn's. Although stress is sometimes claimed to exacerbate Crohn's disease, there is no concrete evidence to support such claim. Dietary microparticles, such as those found in toothpaste, have been studied as they produce effects on immunity, but they were not consumed in greater amounts in patients with Crohn's.

Crohn's disease can lead to several mechanical complications within the intestines, including obstruction, fistulae, and abscesses. Obstruction typically occurs from strictures or adhesions that narrow the lumen, blocking the passage of the intestinal contents. A fistula can develop between two loops of bowel, between the bowel and bladder, between the bowel and vagina, and between the bowel and skin. Abscesses are walled off concentrations of infection, which can occur in the abdomen or in the perianal area. Crohn's is responsible for 10% of vesicoenteric fistulae, and is the most common cause of ileovesical fistulae.

Crohn's disease also increases the risk of cancer in the area of inflammation. For example, individuals with Crohn's disease involving the small bowel are at higher risk for small intestinal cancer. Similarly, people with Crohn's colitis have a relative risk of 5.6 for developing colon cancer. Screening for colon cancer with colonoscopy is recommended for anyone who has had Crohn's colitis for at least eight years. Some studies suggest there is a role for chemoprotection in the prevention of colorectal cancer in Crohn's involving the colon; two agents have been suggested, folate and mesalamine preparations. Also, immunomodulators and biologic agents used to treat this disease may promote developing extra-intestinal cancers.

Individuals with Crohn's disease are at risk of malnutrition for many reasons, including decreased food intake and malabsorption. The risk increases following resection of the small bowel. Such individuals may require oral supplements to increase their caloric intake, or in severe cases, total parenteral nutrition (TPN). Most people with moderate or severe Crohn's disease are referred to a dietitian for assistance in nutrition.

The major significant complications of Crohn's disease include bowel obstruction, abscesses, free perforation and hemorrhage, which in rare cases may be fatal.

Crohn's disease can be problematic during pregnancy, and some medications can cause adverse outcomes for the fetus or mother. Consultation with an obstetrician and gastroenterologist about Crohn's disease and all medications facilitates preventative measures. In some cases, remission occurs during pregnancy. Certain medications can also lower sperm count or otherwise adversely affect a man's fertility.

Evidence does not support a role for specific foods including spicy foods and coffee in the development of peptic ulcers. People are usually advised to avoid foods that bother them.

Gastritis may also develop after major surgery or traumatic injury ("Cushing ulcer"), burns ("Curling ulcer"), or severe infections. Gastritis may also occur in those who have had weight loss surgery resulting in the banding or reconstruction of the digestive tract.

Barrett's esophagus is a premalignant condition. Its malignant sequela, oesophagogastric junctional adenocarcinoma, has a mortality rate of over 85%. The risk of developing esophageal adenocarcinoma in people who have Barrett's esophagus has been estimated to be 6–7 per 1000 person-years, however a cohort study of 11,028 patients from Denmark published in 2011 showed an incidence of only 1.2 per 1000 person-years (5.1 per 1000 person-years in patients with dysplasia, 1.0 per 1000 person-years in patients without dysplasia). The relative risk of esophageal adenocarcinoma is approximately 10 in those with Barret's esophagus, compared to the general population. Most patients with esophageal carcinoma survive less than one year.

Dietary factors such as spice consumption, were hypothesized to cause ulcers until late in the 20th century, but have been shown to be of relatively minor importance. Caffeine and coffee, also commonly thought to cause or exacerbate ulcers, appear to have little effect. Similarly, while studies have found that alcohol consumption increases risk when associated with "H. pylori" infection, it does not seem to independently increase risk. Even when coupled with "H. pylori" infection, the increase is modest in comparison to the primary risk factor.

Barrett's esophagus occurs due to chronic inflammation. The principal cause of the chronic inflammation is gastroesophageal reflux disease, GERD (UK: GORD). In this disease, acidic stomach, bile, and small intestine and pancreatic contents cause damage to the cells of the lower esophagus. Recently, bile acids were shown to be able to induce intestinal differentiation, in gastroesophageal junction cells, through inhibition of the epidermal growth factor receptor (EGFR) and the protein kinase enzyme Akt. This results in the eventual up-regulation of the p50 subunit of protein complex NF-κB ("NFKB1"), and ultimately activation of the homeobox gene "CDX2", which is responsible for the expression of intestinal enzymes such as guanylate cyclase 2C. This mechanism also explains the selection of HER2/neu (also called ERBB2) and the overexpressing (lineage-addicted) cancer cells during the process of carcinogenesis, and the efficacy of targeted therapy against the Her-2 receptor with trastuzumab (Herceptin) in the treatment of adenocarcinomas at the gastroesophageal junction.

Researchers are unable to predict who with heartburn will develop Barrett's esophagus. While no relationship exists between the severity of heartburn and the development of Barrett's esophagus, a relationship does exist between chronic heartburn and the development of Barrett's esophagus. Sometimes, people with Barrett's esophagus have no heartburn symptoms at all. In rare cases, damage to the esophagus may be caused by swallowing a corrosive substance such as lye.

Stress due to serious health problems such as those requiring treatment in an intensive care unit is well described as a cause of peptic ulcers, which are termed stress ulcers.

While chronic life stress was once believed to be the main cause of ulcers, this is no longer the case. It is, however, still occasionally believed to play a role. This may be by increasing the risk in those with other causes such as "H. pylori" or NSAID use.

Gastroesophageal reflux disease (GERD) affects approximately 40% of adults. Strictures occur in 7 to 23% of patients with GERD who are untreated.

Causes

Esophagitis cannot be spread. However, infections can be spread by those who have infectious esophagitis. Esophagitis can develop due to many causes. GERD is the most common cause of esophagitis because of the backflow of acid from the stomach, which can irritate the lining of the esophagus.

Other causes include:

- Medicines- Can cause esophageal damage that can lead to esophageal ulcers

- Nonsteroidal anti-inflammatory drugs (NSAIDS)-aspirin, naproxen sodium, and ibuprofen. Known to irritate the GI tract.

- Antibiotics- doxycycline and tetracycline

- Quinidine

- Biphosphonates- used to treat osteoporosis

- Steroids

- Potassium chloride

- Chemical injury by alkaline or acid solutions

- Physical injury resulting from nasogastric tubes.

- Alcohol abuse- Can wear down the lining of the esophagus.

- Crohn's disease – a type of IBD and an autoimmune disease that can cause esophagitis if it attacks the esophagus.

- Stress- Can cause higher levels of acid reflux

- Radiation therapy-Can affect the immune system.

- Allergies (food, inhalants)- Allergies can stimulate eosinophilic esophagitis.

- Infection-People with an immunodeficiencies have a higher chance of developing esophagitis.

- Vitamins and supplements (iron, Vitamin C, and potassium)-Supplements and minerals can be hard on the GI tract.

- Vomiting- Acid can irritate esophagus.

- Hernias-A hernia can poke through the diaphragm muscle and can inhibit the stomach acid and food from draining quickly.

- Surgery

Prevention

Since there can be many causes underlying esophagitis, it is important to try to find the cause to help to prevent esophagitis. To prevent reflux esophagitis, avoid acidic foods, caffeine, eating before going to bed, alcohol, fatty meals, and smoking. To prevent drug-induced esophagitis, drink plenty of liquids when taking medicines, take an alternative drug, and do not take medicines while lying down, before sleeping, or too many at one time. Esophagitis is more prevalent in adults and does not discriminate.

GERD may lead to Barrett's esophagus, a type of intestinal metaplasia, which is in turn a precursor condition for esophageal cancer. The risk of progression from Barrett's to dysplasia is uncertain, but is estimated at about 20% of cases. Due to the risk of chronic heartburn progressing to Barrett's, EGD every five years is recommended for people with chronic heartburn, or who take drugs for chronic GERD.

GERD is caused by a failure of the lower esophageal sphincter. In healthy patients, the "Angle of His"—the angle at which the esophagus enters the stomach—creates a valve that prevents duodenal bile, enzymes, and stomach acid from traveling back into the esophagus where they can cause burning and inflammation of sensitive esophageal tissue.

Factors that can contribute to GERD:

- Hiatal hernia, which increases the likelihood of GERD due to mechanical and motility factors.

- Obesity: increasing body mass index is associated with more severe GERD. In a large series of 2,000 patients with symptomatic reflux disease, it has been shown that 13% of changes in esophageal acid exposure is attributable to changes in body mass index.

- Zollinger-Ellison syndrome, which can be present with increased gastric acidity due to gastrin production.

- A high blood calcium level, which can increase gastrin production, leading to increased acidity.

- Scleroderma and systemic sclerosis, which can feature esophageal dysmotility.

- The use of medicines such as prednisolone.

- Visceroptosis or Glénard syndrome, in which the stomach has sunk in the abdomen upsetting the motility and acid secretion of the stomach.

GERD has been linked to a variety of respiratory and laryngeal complaints such as laryngitis, chronic cough, pulmonary fibrosis, earache, and asthma, even when not clinically apparent. These atypical manifestations of GERD are commonly referred to as laryngopharyngeal reflux (LPR) or as extraesophageal reflux disease (EERD).

Factors that have been linked with GERD, but not conclusively:

- Obstructive sleep apnea

- Gallstones, which can impede the flow of bile into the duodenum, which can affect the ability to neutralize gastric acid

In 1999, a review of existing studies found that, on average, 40% of GERD patients also had "H. pylori" infection. The eradication of "H. pylori" can lead to an increase in acid secretion, leading to the question of whether "H. pylori"-infected GERD patients are any different than non-infected GERD patients. A double-blind study, reported in 2004, found no clinically significant difference between these two types of patients with regard to the subjective or objective measures of disease severity.

Esophageal diseases can derive from congenital conditions, or they can be acquired later in life.

Many people experience a burning sensation in their chest occasionally, caused by stomach acids refluxing into the esophagus, normally called heartburn. Extended exposure to heartburn may erode the lining of the esophagus, leading potentially to Barrett's esophagus which is associated with an increased risk of adenocarcinoma most commonly found in the distal one-third of the esophagus.

Some people also experience a sensation known as globus esophagus, where it feels as if a ball is lodged in the lower part of the esophagus.

The following are additional diseases and conditions that affect the esophagus:

- Achalasia

- Acute esophageal necrosis

- Barrett's esophagus

- Boerhaave syndrome

- Caustic injury to the esophagus

- Chagas disease

- Diffuse esophageal spasm

- Esophageal atresia and Tracheoesophageal fistula

- Esophageal cancer

- Esophageal dysphagia

- Esophageal varices

- Esophageal web

- Esophagitis

- GERD

- Hiatus hernia

- Jackhammer esophagus (hypercontractile peristalsis)

- Killian–Jamieson diverticulum

- Mallory-Weiss syndrome

- Neurogenic dysphagia

- Nutcracker esophagus

- Schatzki's ring

- Zenker's Diverticulum

The esophagus is a muscular tube made of both voluntary and involuntary muscles. It is responsible for peristalsis of food. It is about 8 inches long and passes through the diaphragm before entering the stomach. The esophagus is made up of four different layers: serosa, muscularis externa, submucosa, and the mucosa. The mucosa, which is the inner most layer and lining of the esophagus, is composed of stratified squamous epithelium, lamina propria, and muscularis mucosae. At the end of the esophagus is the lower esophageal sphincter, which prevents stomach acid from moving to the esophagus. Sometimes the sphincter allows acid to backflow into the esophagus if it is not strong enough. Esophagitis occurs when there is an infection or irritation to the layers of the esophagus. Infection can be caused by bacteria, viruses, fungi, or diseases that weaken the immune system. Irritation can be caused by GERD, vomiting, surgery, medications, hernias, and radiation injury. Inflammation can cause the esophagus to narrow, which makes swallowing food difficult and may result in food bolus impaction. Irritation from the backflow of acid can cause the feeling of burning in the chest and can result in the flow of acid into the throat causing acid reflux or regurgitation . If irritation, infection, and/or inflammation to the esophagus continues, it is likely that the symptoms and signs will increase.

Most damage to the pyloric valve occurs as a complication of gastric surgery. Other causes of biliary reflux may be:

- Peptic ulcer

- Gallbladder surgery (cholecystectomy)

A significant fraction of cases are idiopathic, with no identified specific etiology.

It can be caused by or associated with gastroesophageal reflux disease, esophagitis, a dysfunctional lower esophageal sphincter, disordered motility, lye ingestion, or a hiatal hernia. Strictures can form after esophageal surgery and other treatments such as laser therapy or photodynamic therapy. While the area heals, a scar forms, causing the tissue to pull and tighten, leading to difficulty in swallowing.

Food bolus obstruction is most commonly caused by Schatzki rings, which are mucosal rings of unknown cause in the lower esophagus. Foodstuff jams into the esophagus due to the narrowing caused by the ring. An increasingly commonly recognized cause for esophageal food bolus obstruction is eosinophilic esophagitis, which is an inflammatory disorder of the mucosa of the esophagus, of unknown cause. Many alterations caused by eosinophilic esophagitis can predispose to food boluses; these include the presence of multiple rings and narrowing of the lumen. When considering esophageal dilation to treat a patient with food bolus obstruction, care must be made to look for features of eosinophilic esophagitis, as these patients are at a higher risk of dilation-associated complications.

Other conditions that predispose to food bolus obstructions are esophageal webs and peptic strictures. Food boluses are common in the course of illness in patients with esophageal cancer but are more difficult to treat as endoscopy to push the bolus is less safe. Patients with esophageal self-expandable metallic stents may present with food boluses lodged within the stent lumen. Rarely disorders of movement of the esophagus, such as nutcracker esophagus, can predispose to food bolus obstruction.

The treatment for bile reflux is the same as the treatment for acidic reflux. In general, everything that can

reduce acidic reflux can reduce bile reflux. Examples include lifestyle modification, weight reduction, and the avoidance of eating immediately before sleep or being in the supine position immediately after meals. In addition, smoking has been found to be a factor in the development of acidic reflux. Thus, all of these factors should be applied to bile reflux as well.

Likewise, drugs that reduce the secretion of gastric acid (e.g., proton pump inhibitors)

or that reduce gastric contents or volume can be used to treat acidic bile reflux. Because prokinetic drugs increase the motility of the stomach and accelerate gastric emptying, they can also reduce bile reflux. Other drugs that reduce the relaxations of the lower esophageal sphincter, such as baclofen, have also proven to reduce bile reflux, particularly in patients who are refractory to (medically unresponsive to) proton pump inhibitor therapy.

Medications used in managing biliary reflux include bile acid sequestrants, particularly cholestyramine, which disrupt the circulation of bile in the digestive tract and sequester bile that would otherwise cause symptoms when refluxed; and prokinetic agents, to move material from the stomach to the small bowel more rapidly and prevent reflux.

Biliary reflux may also be treated surgically, if medications are ineffective or if precancerous tissue is present in the esophagus.

They are mainly observed in the Plummer–Vinson syndrome, which is associated with chronic iron deficiency anemia. One in 10 patients with Plummer-Vinson syndrome will eventually develop squamous cell carcinoma of the esophagus, but it is unclear if esophageal webs in and of themselves are a risk factor.

Esophageal webs are associated with bullous diseases (such as epidermolysis bullosa, pemphigus, and bullous pemphigoid), with graft versus host disease involving the esophagus, and with celiac disease.

Esophageal webs are more common in white individuals and in women (with a ratio 2:1). The literature describes relations between these webs and Plummer-Vinson Syndrome, bullous dermatologic disorders, inlet patch, graft-versus-host disease and celiac disease. The postulated mechanisms are sideropenic anemia (mechanism unknown) or some interference of the immune system.

Esophageal webs can be ruptured during upper endoscopy.

About 6 to 14 percent of patients who receive a routine barium swallow test of the esophagus are found to have a Schatzki ring.

If there is dysphagia to both solids and liquids, then it is most likely a motility problem. If there is dysphagia initially to solids but progresses to also involve liquids, then it is most likely a mechanical obstruction. Once a distinction has been made between a motility problem and a mechanical obstruction, it is important to note whether the dysphagia is intermittent or progressive. An intermittent motility dysphagia likely can be diffuse esophageal spasm (DES) or nonspecific esophageal motility disorder (NEMD). Progressive motility dysphagia disorders include scleroderma or achalasia with chronic heartburn, regurgitation, respiratory problems, or weight loss. Intermittent mechanical dysphagia is likely to be an esophageal ring. Progressive mechanical dysphagia is most likely due to peptic stricture or esophageal cancer.

Many foods can lodge themselves in the esophagus, but the most common are meats such as steak, poultry, or pork leading to the colourful description of the phenomenon as steakhouse syndrome. People with food bolus obstruction typically display acute dysphagia (difficulty swallowing), often to the point that they cannot even swallow their saliva, leading to drooling. They may also suffer from chest pain, neck pain, regurgitation of food, or painful swallowing (odynophagia).

Patients with esophageal food boluses are also at risk of complications, such as perforation of the esophagus, and aspiration into the lungs. As a result, urgent treatment of patients with high-risk features, or a lengthy duration of symptoms, is recommended.

Esophageal stricture, or narrowing of the esophagus, is usually a complication of acid reflux, most commonly due to gastroesophageal reflux (GERD). These patients are usually older and have had GERD for a long time. Esophageal stricture can also be due to other causes, such as acid reflux from Zollinger-Ellison syndrome, trauma from a nasogastric tube placement, and chronic acid exposure in patients with poor esophageal motility from scleroderma. Other non-acid related causes of peptic strictures include infectious esophagitis, ingestion of chemical irritant, pill irritation, and radiation. Peptic stricture is a progressive mechanical dysphagia, meaning patients will complain of initial intolerance to solids followed by inability to tolerate liquids. When the diameter of the stricture is less than 12 mm the patient will always have dysphagia, while dysphagia is not seen when the diameter of the stricture is above 30 mm. Symptoms relating to the underlying cause of the stricture usually will also be present.

Esophageal cancer also presents with progressive mechanical dysphagia. Patients usually come with

rapidly progressive dysphagia first with solids then with liquids, weight loss (> 10 kg), and anorexia (loss of appetite). Esophageal cancer usually affects the elderly. Esophageal cancers can be either squamous cell carcinoma or adenocarcinoma. Adenocarcinoma is the most prevalent in the US and is associated with patients with chronic GERD who have developed Barrett's esophagus (intestinal metaplasia of esophageal mucosa). Squamous cell carcinoma is more prevalent in Asia and is associated with tobacco smoking and alcohol use.

Esophageal rings and webs, are actual rings and webs of tissue that may occlude the esophageal lumen.

- "Rings" --- Also known as Schatzki rings from the discoverer, these rings are usually mucosal rings rather than muscular rings, and are located near the gastroesophageal junction at the squamo-columnar junction. Presence of multiple rings may suggest eosinophilic esophagitis. Rings cause intermittent mechanical dysphagia, meaning patients will usually present with transient discomfort and regurgitation while swallowing solids and then liquids, depending on the constriction of the ring.

- "Webs" --- Usually squamous mucosal protrusion into the esophageal lumen, especially anterior cervical esophagus behind the cricoid area. Patients are usually asymptomatic or have intermittent dysphagia. An important association of esophageal webs is to the Plummer-Vinson syndrome in iron deficiency, in which case patients will also have anemia, koilonychia, fatigue, and other symptoms of anemia.

Achalasia is an idiopathic motility disorder characterized by failure of lower esophageal sphincter (LES) relaxation as well as loss of peristalsis in the distal esophagus, which is mostly smooth muscle. Both of these features impair the ability of the esophagus to empty contents into the stomach. Patients usually complain of dysphagia to both solids and liquids. Dysphagia to liquids, in particular, is a characteristic of achalasia. Other symptoms of achalasia include regurgitation, night coughing, chest pain, weight loss, and heartburn. The combination of achalasia, adrenal insufficiency, and alacrima (lack of tear production) in children is known as the triple A (Allgrove) syndrome. In most cases the cause is unknown (idiopathic), but in some regions of the world, achalasia can also be caused by Chagas disease due to infection by "Trypanosoma cruzi".

Scleroderma is a disease characterized by atrophy and sclerosis of the gut wall, most commonly of the distal esophagus (~90%). Consequently, the lower esophageal sphincter cannot close and this can lead to severe gastroesophageal reflux disease (GERD). Patients typically present with progressive dysphagia to both solids and liquids secondary to motility problems or peptic stricture from acid reflux.

Spastic motility disorders include diffuse esophageal spasm (DES), nutcracker esophagus, hypertensive lower esophageal sphincter, and nonspecific spastic esophageal motility disorders (NEMD).

- "DES" can be caused by many factors that affect muscular or neural functions, including acid reflux, stress, hot or cold food, or carbonated drinks. Patients present with intermittent dysphagia, chest pain, or heartburn.

Rare causes of esophageal dysphagia not mentioned above

- Diverticulum

- Aberrant subclavian artery, or (dysphagia lusoria)

- Cervical osteophytes

- Enlarged aorta

- Enlarged left atrium

- Mediastinal tumor

The two major risk factors for esophageal squamous-cell carcinoma are tobacco (smoking or chewing) and alcohol. The combination of tobacco and alcohol has a strong synergistic effect. Some data suggest that about half of all cases are due to tobacco and about one-third to alcohol, while over three-quarters of the cases in men are due to the combination of smoking and heavy drinking. Risks associated with alcohol appear to be linked to its aldehyde metabolite and to mutations in certain related enzymes. Such metabolic variants are relatively common in Asia.

Other relevant risk factors include regular consumption of very hot drinks (over 65 °C)(149 Fahrenheit) and ingestion of caustic substances. High levels of dietary exposure to nitrosamines (chemical compounds found both in tobacco smoke and certain foodstuffs) also appear to be a relevant risk factor. Unfavorable dietary patterns seem to involve exposure to nitrosamines through processed and barbecued meats, pickled vegetables, etc., and a low intake of fresh foods. Other associated factors include nutritional deficiencies, low socioeconomic status, and poor oral hygiene. Chewing betel nut (areca) is an important risk factor in Asia.

Physical trauma may increase the risk. This may include the drinking of very hot drinks.

Having cancer (current or previous) is currently one of the most prevalent out of all conditions among patients. High blood pressure, Chronic lung conditions, Alcohol abuse, Kidney failure, Malnutrition are another major risk factors.