The main symptom is vomiting, which typically occurs after meals of undigested food, devoid of any bile. A history of previous peptic ulcers and loss of weight is not uncommon. In advanced cases, signs to look for on physical examination are wasting and dehydration. Visible peristalsis from left to right may be present. Succussion splash is a splash-like sound heard over the stomach in the left upper quadrant of the abdomen on shaking the patient, with or without the stethoscope. Bowel sound may be increased due to excessive peristaltic action of stomach. Fullness in left hypochondrium may also be present.

In the stomach there is a slight balance between acid and the wall lining which is protected by mucus. When this mucus lining is disrupted for whatever reason, signs and symptoms of acidity result. This may result in upper abdominal pain, indigestion, loss of appetite, nausea, vomiting and heartburn. When the condition is allowed to progress, the pain may become continuous; blood may start to leak and be seen in the stools. If the bleeding is rapid and of adequate volume it may even result in vomiting of bright red blood (hematemesis). When the acidity is uncontrolled, it can even cause severe blood loss (anemia) or lead to perforation (hole) in the stomach which is a surgical emergency. In many individuals, the progressive bleeding from an ulcer mixes with the feces and presents as black stools. Presence of blood in stools is often the first sign that there is a problem in the stomach.

Crohn's disease is an inflammatory bowel disease that can affect any part of the digestive tract, even the stomach, although it's a rare presentation. Its main feature is inflammatory ulcers that can affect the total thickness of the stomach wall and can bleed but rarely perforate.

Symptoms include abdominal pain, loss of appetite, and weight loss. Diarrhea is also a symptom that can develop, so checking stools for the appearance of blood is important. It is possible for symptoms of Crohn's disease to remain with a person for weeks or go away on their own. Reporting the symptoms to a doctor is recommended to prevent further complications.

Gastric outlet obstruction (GOO) is a medical condition where there is an obstruction at the level of the pylorus, which is the outlet of the stomach. Individuals with gastric outlet obstruction will often have recurrent vomiting of food that has accumulated in the stomach, but which cannot pass into the small intestine due to the obstruction. The stomach often dilates to accommodate food intake and secretions. Causes of gastric outlet obstruction include both benign causes (such as peptic ulcer disease affecting the area around the pylorus), as well as malignant causes, such as gastric cancer.

Causation related to ulcers may involve severe pain which the patient may interpret as a heart condition/attack.

Treatment of the condition depends upon the underlying cause; it can involve antibiotic treatment when Helicobacter pylori is related to an ulcer, endoscopic therapies (such as dilation of the obstruction with balloons or the placement of self expandable metallic stents), other medical therapies, or surgery to resolve the obstruction.

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.

A gastrojejunocolic fistula is a disorder of the human gastrointestinal tract. It may form between the transverse colon and the upper jejunum after a Billroth II surgical procedure. (The Billroth procedure attaches the jejunum to the remainder of the stomach). Fecal matter thereby passes improperly from the colon to the stomach, and causes halitosis.

Patients may present with diarrhea, weight loss and halitosis as a result of fecal matter passing through the fistula from the colon into the stomach.

Symptoms are not necessarily distinguishable from other kinds of distress. A dog might stand uncomfortably and seem to be in extreme discomfort for no apparent reason. Other possible symptoms include firm distension of the abdomen, weakness, depression, difficulty breathing, hypersalivation, and retching without producing any vomitus ("non-productive vomiting"). A high rate of dogs with GDV have cardiac arrhythmias (40 percent in one study). Chronic GDV may occur in dogs, symptoms of which include loss of appetite, vomiting and weight loss.

Biliary reflux, bile reflux or duodenogastric reflux is a condition that occurs when bile flows upward (refluxes) from the duodenum into the stomach and esophagus.

Biliary reflux can be confused with acid reflux, also known as gastroesophageal reflux disease (GERD). While bile reflux involves fluid from the small intestine flowing into the stomach and esophagus, acid reflux is backflow of stomach acid into the esophagus. These conditions are often related, and differentiating between the two can be difficult.

Bile is a digestive fluid made by the liver, stored in the gallbladder, and discharged into duodenum after food is ingested to aid in the digestion of fat. Normally, the pyloric sphincter prevents bile from entering the stomach. When the pyloric sphincter is damaged or fails to work correctly, bile can enter the stomach and then be transported into the esophagus as in gastric reflux. The presence of small amounts of bile in the stomach is relatively common and usually asymptomatic, but excessive refluxed bile causes irritation and inflammation.

The most common symptoms of GERD in adults are an acidic taste in the mouth, regurgitation, and heartburn. Less common symptoms include pain with swallowing/sore throat, increased salivation (also known as water brash), nausea, chest pain, and coughing.

GERD sometimes causes injury of the esophagus. These injuries may include one or more of the following:

- Reflux esophagitis – inflammation of esophageal epithelium which can cause ulcers near the junction of the stomach and esophagus

- Esophageal strictures – the persistent narrowing of the esophagus caused by reflux-induced inflammation

- Barrett's esophagus – intestinal metaplasia (changes of the epithelial cells from squamous to intestinal columnar epithelium) of the distal esophagus

- Esophageal adenocarcinoma – a form of cancer

Some researchers have proposed that recurrent ear infections, and idiopathic pulmonary fibrosis might be tied, in some cases, to GERD; however, a causative role has not been established. GERD does not appear to be linked to chronic sinusitis.

Signs and symptoms of a peptic ulcer can include one or more of the following:

- abdominal pain, classically epigastric strongly correlated to mealtimes. In case of duodenal ulcers the pain appears about three hours after taking a meal;

- bloating and abdominal fullness;

- waterbrash (rush of saliva after an episode of regurgitation to dilute the acid in esophagus - although this is more associated with gastroesophageal reflux disease);

- nausea and copious vomiting;

- loss of appetite and weight loss;

- hematemesis (vomiting of blood); this can occur due to bleeding directly from a gastric ulcer, or from damage to the esophagus from severe/continuing vomiting.

- melena (tarry, foul-smelling feces due to presence of oxidized iron from hemoglobin);

- rarely, an ulcer can lead to a gastric or duodenal perforation, which leads to acute peritonitis, extreme, stabbing pain, and requires immediate surgery.

A history of heartburn, gastroesophageal reflux disease (GERD) and use of certain forms of medication can raise the suspicion for peptic ulcer. Medicines associated with peptic ulcer include NSAIDs (non-steroid anti-inflammatory drugs) that inhibit cyclooxygenase, and most glucocorticoids (e.g. dexamethasone and prednisolone).

In people over the age of 45 with more than two weeks of the above symptoms, the odds for peptic ulceration are high enough to warrant rapid investigation by esophagogastroduodenoscopy.

The timing of the symptoms in relation to the meal may differentiate between gastric and duodenal ulcers: A gastric ulcer would give epigastric pain during the meal, as gastric acid production is increased as food enters the stomach. Symptoms of duodenal ulcers would initially be relieved by a meal, as the pyloric sphincter closes to concentrate the stomach contents, therefore acid is not reaching the duodenum. Duodenal ulcer pain would manifest mostly 2–3 hours after the meal, when the stomach begins to release digested food and acid into the duodenum.

Also, the symptoms of peptic ulcers may vary with the location of the ulcer and the person's age. Furthermore, typical ulcers tend to heal and recur and as a result the pain may occur for few days and weeks and then wane or disappear. Usually, children and the elderly do not develop any symptoms unless complications have arisen.

Burning or gnawing feeling in the stomach area lasting between 30 minutes and 3 hours commonly accompanies ulcers. This pain can be misinterpreted as hunger, indigestion or heartburn. Pain is usually caused by the ulcer but it may be aggravated by the stomach acid when it comes into contact with the ulcerated area. The pain caused by peptic ulcers can be felt anywhere from the navel up to the sternum, it may last from few minutes to several hours and it may be worse when the stomach is empty. Also, sometimes the pain may flare at night and it can commonly be temporarily relieved by eating foods that buffer stomach acid or by taking anti-acid medication. However, peptic ulcer disease symptoms may be different for every sufferer.

GERD may be difficult to detect in infants and children, since they cannot describe what they are feeling and indicators must be observed. Symptoms may vary from typical adult symptoms. GERD in children may cause repeated vomiting, effortless spitting up, coughing, and other respiratory problems, such as wheezing. Inconsolable crying, refusing food, crying for food and then pulling off the bottle or breast only to cry for it again, failure to gain adequate weight, bad breath, and burping are also common. Children may have one symptom or many; no single symptom is universal in all children with GERD.

Of the estimated 4 million babies born in the US each year, up to 35% of them may have difficulties with reflux in the first few months of their lives, known as 'spitting up'. One theory for this is the "fourth trimester theory" which notes most animals are born with significant mobility, but humans are relatively helpless at birth, and suggests there may have once been a fourth trimester, but children began to be born earlier, evolutionarily, to accommodate the development of larger heads and brains and allow them to pass through the birth canal and this leaves them with partially undeveloped digestive systems.

Most children will outgrow their reflux by their first birthday. However, a small but significant number of them will not outgrow the condition. This is particularly true when a family history of GERD is present.

Gastric dilatation volvulus (GDV), also known as twisted stomach or gastric torsion, is a medical condition in which the stomach becomes overstretched and rotated by excessive gas content. The word "bloat" is often used as a general term to mean gas distension without stomach torsion (a normal change after eating), or to refer to GDV.

GDV is a life-threatening condition in dogs that requires prompt treatment. It is common in certain dog breeds; deep-chested breeds are especially at risk. Mortality rates in dogs range from 10 to 60 percent, even with treatment. With surgery, the mortality rate is 15 to 33 percent.

In an organoaxial gastric volvulus, the stomach rotates around an axis that connects the gastroesophageal junction and the pylorus. The antrum rotates in opposite direction to the fundus of the stomach.This is the most common type of gastric volvulus, occurring in approximately 59% of cases, and it is usually associated with diaphragmatic defects. Strangulation and necrosis commonly occur with organoaxial gastric volvulus and have been reported in 5–28% of cases.

Gastric volvulus or volvulus of stomach is a twisting of all or part of the stomach by more than 180 degrees with obstruction of the flow of material through the stomach, variable loss of blood supply and possible tissue death. The twisting can occur around the long axis of the stomach: this is called organoaxial or around the axis perpendicular to this, called mesenteroaxial. Obstruction is more likely in organoaxial twisting than with mesenteroaxial while the latter is more associated with ischemia. About one third of the cases are associated with a hiatus hernia. Treatment is surgical.

The classic triad (Borchardt's Triad) of gastric volvulus, described by Borchardt in 1904, consists of severe epigastric pain, retching (due to sour taste in mouth) without vomiting, inability to pass a nasogastric tube and reportedly occurs in 70% of cases. Sometimes severe pain at the top of left shoulder, this may be due to internal bleeding irritating the diaphragm upon respiration.

Signs and symptoms may include a sudden pain in the epigastrium to the right of the midline indicating the perforation of a duodenal ulcer. In a gastric ulcer perforation creates a history of burning pain in epigastrium, with flatulence and dyspepsia.

In intestinal perforation, pain starts from the site of perforation and spreads across the abdomen.

Gastrointestinal perforation results in severe abdominal pain intensified by movement, nausea, vomiting and hematemesis. Later symptoms include fever and or chills. In any case, the abdomen becomes rigid with tenderness and rebound tenderness. After some time the abdomen becomes silent and heart sounds can be heard all over. Patient stops passing flatus and motion, abdomen is distended.

The symptoms of esophageal rupture may include sudden onset of chest pain.

Peptic ulcer disease (PUD) is a break in the lining of the stomach, first part of the small intestine or occasionally the lower esophagus. An ulcer in the stomach is known as a gastric ulcer while that in the first part of the intestines is known as a duodenal ulcer. The most common symptoms of a duodenal ulcer are waking at night with upper abdominal pain or upper abdominal pain that improves with eating. With a gastric ulcer the pain may worsen with eating. The pain is often described as a burning or dull ache. Other symptoms include belching, vomiting, weight loss, or poor appetite. About a third of older people have no symptoms. Complications may include bleeding, perforation and blockage of the stomach. Bleeding occurs in as many as 15% of people.

Common causes include the bacteria "Helicobacter pylori" and non-steroidal anti-inflammatory drugs (NSAIDs). Other less common causes include tobacco smoking, stress due to serious illness, Behcet disease, Zollinger-Ellison syndrome, Crohn disease and liver cirrhosis, among others. Older people are more sensitive to the ulcer-causing effects of NSAIDs. The diagnosis is typically suspected due to the presenting symptoms with confirmation by either endoscopy or barium swallow. "H. pylori" can be diagnosed by testing the blood for antibodies, a urea breath test, testing the stool for signs of the bacteria, or a biopsy of the stomach. Other conditions that produce similar symptoms include stomach cancer, coronary heart disease, and inflammation of the stomach lining or gallbladder inflammation.

Diet does not play an important role in either causing or preventing ulcers. Treatment includes stopping smoking, stopping NSAIDs, stopping alcohol and giving medications to decrease stomach acid. The medication used to decrease acid is usually either a proton pump inhibitor (PPI) or an H2 blocker with four weeks of treatment initially recommended. Ulcers due to "H. pylori" are treated with a combination of medications such as amoxicillin, clarithromycin and a PPI. Antibiotic resistance is increasing and thus treatment may not always be effective. Bleeding ulcers may be treated by endoscopy, with open surgery typically only used in cases in which it is not successful.

Peptic ulcers are present in around 4% of the population. Newly ulcers were found in around 87.4 million people worldwide during 2015. About 10% of people develop a peptic ulcer at some point in their life. They resulted in 267,500 deaths in 2015 down from 327,000 deaths in 1990. The first description of a perforated peptic ulcer was in 1670 in Princess Henrietta of England. "H. pylori" was first identified as causing peptic ulcers by Barry Marshall and Robin Warren in the late 20th century, a discovery for which they received the Nobel Prize in 2005.

Underlying causes include gastric ulcers, duodenal ulcers, appendicitis, gastrointestinal cancer, diverticulitis, inflammatory bowel disease, superior mesenteric artery syndrome, trauma and ascariasis. Typhoid fever, non-steroidal anti-inflammatory drugs, ingestion of corrosives may also be responsible.

Many people with gastritis experience no symptoms at all. However, upper central abdominal pain is the most common symptom; the pain may be dull, vague, burning, aching, gnawing, sore, or sharp. Pain is usually located in the upper central portion of the abdomen, but it may occur anywhere from the upper left portion of the abdomen around to the back.

Other signs and symptoms may include the following:

- Nausea

- Vomiting (if present, may be clear, green or yellow, blood-streaked, or completely bloody, depending on the severity of the stomach inflammation)

- Belching (if present, usually does not relieve the pain much)

- Bloating

- Early satiety

- Loss of appetite

- Unexplained weight loss

Hiatal hernia has often been called the "great mimic" because its symptoms can resemble many disorders. Among them, a person with a hiatal hernia can experience dull pains in the chest, shortness of breath (caused by the hernia's effect on the diaphragm), heart palpitations (due to irritation of the vagus nerve), and swallowed food "balling up" and causing discomfort in the lower esophagus until it passes on to the stomach. In addition, hiatal hernias often result in heartburn but may also cause chest pain or pain with eating.

In most cases however, a hiatal hernia does not cause any symptoms. The pain and discomfort that a patient experiences is due to the reflux of gastric acid, air, or bile. While there are several causes of acid reflux, it occurs more frequently in the presence of hiatal hernia.

In newborns, the presence of Bochdalek hernia can be recognised from symptoms such as difficulty breathing fast respiration, increased heart rate.

The most common symptoms of gastroparesis are the following:

- Chronic nausea (93%)

- Vomiting (especially of undigested food) (68–84%)

- Abdominal pain (46–90%)

- A feeling of fullness after eating just a few bites (60–86%)

Other symptoms include the following:

- Abdominal bloating

- Body aches (myalgia)

- Erratic blood glucose levels

- Gastroesophageal reflux (GERD)

- Heartburn

- Lack of appetite

- Morning nausea

- Muscle weakness

- Night sweats

- Palpitations

- Spasms of the stomach wall

- Constipation or infrequent bowel movements

- Weight loss and malnutrition

Morning nausea may also indicate gastroparesis. Vomiting may not occur in all cases, as sufferers may adjust their diets to include only small amounts of food.

Prognosis is usually very good, although complications are more likely to occur when there are serious congenital anomalies. Late complications may occur in about 12 percent of patients with duodenal atresia, and the mortality rate for these complications is 6 percent.

The following are risk factors that can result in a hiatus hernia.

- Increased pressure within the abdomen caused by:

- Heavy lifting or bending over

- Frequent or hard coughing

- Hard sneezing

- Violent vomiting

- Straining

- Stress

Duodenal cancer is a cancer in the beginning section of the small intestine. It is relatively rare compared to gastric cancer and colorectal cancer. Its histology is usually adenocarcinoma.

Familial adenomatous polyposis (FAP), Gardner syndrome, Lynch syndrome, Muir–Torre syndrome, celiac disease, Peutz–Jeghers syndrome, Crohn's disease and juvenile polyposis syndrome are risk factors for developing this cancer.

The duodenum is the first part of the small intestine. It is located between the stomach and the jejunum. After foods combine with stomach acid, they descend into the duodenum where they mix with bile from the gallbladder and digestive juices from the pancreas.

Duodenal atresia, also known as duodenojejunal atresia, is the congenital absence or complete closure of a portion of the lumen of the duodenum. It causes increased levels of amniotic fluid during pregnancy (polyhydramnios) and intestinal obstruction in newborn babies. Radiography shows a distended stomach and distended duodenum, which are separated by the pyloric valve, a finding described as the double-bubble sign.

Treatment includes suctioning out any fluid that is trapped in the stomach, providing fluids intravenously, and surgical repair of the intestinal closure.

The signs and symptoms for esophagitis include:

- Heartburn feels like the inside of your chest is burning. It is a symptom of acid reflux or GERD.

- Nausea is the feeling of being sick, specifically with the urge to vomit.

- Swallowing is painful and difficult to pass food through your throat into your esophagus.

- Vomiting, also known as emesis, is the release of the contents of the stomach through the mouth or nose.

- Abdominal pain is when pain is felt in the abdomen.

- Food bolus impaction is an obstruction of the esophagus by swallowed food.

- Acid regurgitation is the backflow of acid from the stomach to the mouth.

- Chest pain is pain felt between the neck and upper abdomen. There are many causes and the pain can range.

- Cough is a reflex to clear the throat of irritants or mucus.

A doctor should be consulted if the signs and/or symptoms do not subside after a few days, are accompanied with flu-like symptoms, do not lessen after treating with over-the counter antacids, and/or make eating food difficult.