Other radiological studies frequently used to assess patients with chronic stomach problems include a barium swallow, where a dye is consumed and pictures of the esophagus and stomach are obtained every few minutes. Other tests include a 24-hour pH study, CT scans or MRI.

There are many tools for investigating stomach problems. The most common is endoscopy. This procedure is performed as an outpatient and utilizes a small flexible camera. The procedure does require intravenous sedation and takes about 30–45 minutes; the endoscope is inserted via the mouth and can visualize the entire swallowing tube, stomach and duodenum. The procedure also allows the physician to obtain biopsy samples. In many cases of bleeding, the surgeon can use the endoscope to treat the source of bleeding with laser, clips or other injectable drugs.

The most confirmatory investigation is endoscopy of upper gastrointestinal tract.

Laboratory

- Individuals with gastric outlet obstruction are often hypochloremic, hypokalemic, and alkalotic due to loss of hydrogen chloride and potassium. High urea and creatinine levels may also be observed if the patient is dehydrated.

Abdominal X-ray

- A gastric fluid level may be seen which would support the diagnosis.

Barium meal and follow through

- May show an enlarged stomach and pyloroduodenal stenosis.

Gastroscopy

- May help with cause and can be used therapeutically.

The differential diagnosis of gastric outlet obstruction may include: early gastric carcinoma hiatal hernia, gastroesophageal reflux, adrenal insufficiency, and inborn errors of metabolism.

For practical purposes, gastric pH an endoscopy should be done in someone with suspected achlorhydria. Older testing methods using fluid aspiration through a nasogastric tube can be done, but these procedures can cause significant discomfort and are less efficient ways to obtain a diagnosis.

A complete 24-hour profile of gastric acid secretion is best obtained during an esophageal pH monitoring study.

Achlorhydria may also be documented by measurements of extremely low levels of pepsinogen A (PgA) () in blood serum. The diagnosis may be supported by high serum gastrin levels ().

The "Heidelberg test" is an alternative way to measure stomach acid and diagnose hypochlorhydria/achlorhydria.

A check can exclude deficiencies in iron, calcium, prothrombin time, vitamin B-12, vitamin D, and thiamine. Complete blood count with indices and peripheral smears can be examined to exclude anemia. Elevation of serum folate is suggestive of small bowel bacterial overgrowth. Bacterial folate can be absorbed into the circulation.

Once achlorhydria is confirmed, a hydrogen breath test can check for bacterial overgrowth.

The diagnosis is mainly established based on the characteristic symptoms. Stomach pain is usually the first signal of a peptic ulcer. In some cases, doctors may treat ulcers without diagnosing them with specific tests and observe whether the symptoms resolve, thus indicating that their primary diagnosis was accurate.

More specifically, peptic ulcers erode the muscularis mucosae, at minimum reaching to the level of the submucosa (contrast with erosions, which do not involve the muscularis mucosae).

Confirmation of the diagnosis is made with the help of tests such as endoscopies or barium contrast x-rays. The tests are typically ordered if the symptoms do not resolve after a few weeks of treatment, or when they first appear in a person who is over age 45 or who has other symptoms such as weight loss, because stomach cancer can cause similar symptoms. Also, when severe ulcers resist treatment, particularly if a person has several ulcers or the ulcers are in unusual places, a doctor may suspect an underlying condition that causes the stomach to overproduce acid.

An esophagogastroduodenoscopy (EGD), a form of endoscopy, also known as a gastroscopy, is carried out on people in whom a peptic ulcer is suspected. By direct visual identification, the location and severity of an ulcer can be described. Moreover, if no ulcer is present, EGD can often provide an alternative diagnosis.

One of the reasons that blood tests are not reliable for accurate peptic ulcer diagnosis on their own is their inability to differentiate between past exposure to the bacteria and current infection. Additionally, a false negative result is possible with a blood test if the person has recently been taking certain drugs, such as antibiotics or proton-pump inhibitors.

The diagnosis of "Helicobacter pylori" can be made by:

- Urea breath test (noninvasive and does not require EGD);

- Direct culture from an EGD biopsy specimen; this is difficult to do, and can be expensive. Most labs are not set up to perform "H. pylori" cultures;

- Direct detection of urease activity in a biopsy specimen by rapid urease test;

- Measurement of antibody levels in the blood (does not require EGD). It is still somewhat controversial whether a positive antibody without EGD is enough to warrant eradication therapy;

- Stool antigen test;

- Histological examination and staining of an EGD biopsy.

The breath test uses radioactive carbon to detect H. pylori. To perform this exam the person will be asked to drink a tasteless liquid which contains the carbon as part of the substance that the bacteria breaks down. After an hour, the person will be asked to blow into a bag that is sealed. If the person is infected with H. pylori, the breath sample will contain radioactive carbon dioxide. This test provides the advantage of being able to monitor the response to treatment used to kill the bacteria.

The possibility of other causes of ulcers, notably malignancy (gastric cancer) needs to be kept in mind. This is especially true in ulcers of the "greater (large) curvature" of the stomach; most are also a consequence of chronic "H. pylori" infection.

If a peptic ulcer perforates, air will leak from the inside of the gastrointestinal tract (which always contains some air) to the peritoneal cavity (which normally never contains air). This leads to "free gas" within the peritoneal cavity. If the person stands erect, as when having a chest X-ray, the gas will float to a position underneath the diaphragm. Therefore, gas in the peritoneal cavity, shown on an erect chest X-ray or supine lateral abdominal X-ray, is an omen of perforated peptic ulcer disease.

Zollinger–Ellison syndrome may be suspected when the above symptoms prove resistant to treatment, when the symptoms are especially suggestive of the syndrome, or when endoscopy is suggestive. The diagnosis is made through several laboratory tests and imaging studies:

- Secretin stimulation test, which measures evoked gastrin levels

- Fasting gastrin levels on at least three separate occasions

- Gastric acid secretion and pH (normal basal gastric acid secretion is less than 10 mEq/hour; in Zollinger–Ellison patients, it is usually more than 15 mEq/hour)

- An increased level of chromogranin A is a common marker of neuroendocrine tumors.

In addition, the source of the increased gastrin production must be determined using MRI or somatostatin receptor scintigraphy.

Often, a diagnosis can be made based on the patient's description of their symptoms, but other methods which may be used to verify gastritis include:

- Blood tests:

- Blood cell count

- Presence of "H. pylori"

- Liver, kidney, gallbladder, or pancreas functions

- Urinalysis

- Stool sample, to look for blood in the stool

- X-rays

- ECGs

- Endoscopy, to check for stomach lining inflammation and mucous erosion

- Stomach biopsy, to test for gastritis and other conditions

A physical examination may reveal a mass or distention of the abdomen.

Tests which may be useful for diagnosis include:

- Abdominal x-ray

- Abdominal CT scan

- Contrast enema study

Other possible causes (eg differential diagnosis) of large folds within the stomach include: Zollinger-Ellison syndrome, cancer, infection (cytomegalovirus/CMV, histoplasmosis, syphilis), and infiltrative disorders such as sarcoidosis.

The large folds of the stomach, as seen in Ménétrier disease, are easily detected by x-ray imaging following a barium meal or by endoscopic methods. Endoscopy with deep mucosal biopsy (and cytology) is required to establish the diagnosis and exclude other entities that may present similarly. A non-diagnostic biopsy may lead to a surgically obtained full-thickness biopsy to exclude malignancy. CMV and helicobacter pylori serology should be a part of the evaluation.

Twenty-four-hour pH monitoring reveals hypochlorhydria or achlorhydria, and a chromium-labelled albumin test reveals increased GI protein loss. Serum gastrin levels will be within normal limits.

On chest radiography, a retrocardiac, gas-filled viscus may be seen in cases of intrathoracic stomach, which confirms the diagnosis. Plain abdominal radiography reveals a massively distended viscus in the upper abdomen. In organoaxial volvulus, plain films may show a horizontally oriented stomach with a single air-fluid level and a paucity of distal gas. In mesenteroaxial volvulus, plain abdominal radiographic findings include a spherical stomach on supine images and 2 air-fluid levels on erect images, with the antrum positioned superior to the fundus.

- Upper GI contrast studies:

The diagnosis of gastric volvulus is usually based on barium studies; however, some authors recommend computed tomography (CT) scanning as the imaging modality of choice.

Upper gastrointestinal (GI) contrast radiographic studies (using barium or Gastrografin) are sensitive and specific if performed with the stomach in the "twisted" state and may show an upside-down stomach. Contrast studies have been reported to have a diagnostic yield in 81–84% of patients.

Often performed for an evaluation of acute abdominal pain, a computed tomography (CT) scan can offer immediate diagnosis by showing two bubbles with a transition line. Proponents of CT scanning in the diagnosis of gastric volvulus report several benefits, including:

1. the ability to rapidly diagnose the condition based on a few coronal reconstructed images,

2. the ability to detect the presence or absence of gastric pneumatosis and free air,

3. the detection of predisposing factors (i.e., diaphragmatic or hiatal hernias), and

4. the exclusion of other abdominal pathology.

- Endoscopy:

Upper gastrointestinal (GI) endoscopy may be helpful in the diagnosis of gastric volvulus. When this procedure reveals distortion of the gastric anatomy with difficulty intubating the stomach or pylorus, it can be highly suggestive of gastric volvulus. In the late stage of gastric volvulus, strangulation of the blood supply can result in progressive ischemic ulceration or mucosal fissuring.

The nonoperative mortality rate for gastric volvulus is reportedly as high as 80%. Historically, mortality rates of 30–50% have been reported for acute gastric volvulus, with the major cause of death being strangulation, which can lead to necrosis and perforation. With advances in diagnosis and management, the mortality rate from acute gastric volvulus is 15–20% and that for chronic gastric volvulus is 0–13%.

A health care provider will diagnose dumping syndrome primarily on the basis of symptoms. The following tests may also help confirm dumping syndrome and exclude other conditions with similar symptoms:

- A modified oral glucose tolerance test checks how well insulin works with tissues to absorb glucose. A health care provider often confirms dumping syndrome in people with:

- low blood sugar between 120 and 180 minutes after drinking the solution

- an increase in hematocrit of more than 3 percent at 30 minutes

- a rise in pulse rate of more than 10 beats per minute after 30 minutes

- A gastric emptying scintigraphy test involves eating a bland meal that contains a small amount of radioactive material. An external camera scans the abdomen to locate the radioactive material. The radiologist measures the rate of gastric emptying at 1, 2, 3, and 4 hours after the meal. The test can help confirm a diagnosis of dumping syndrome.

The health care provider may also examine the structure of the esophagus, stomach, and upper small intestine with the following tests:

- An upper GI endoscopy to see the upper GI tract. A gastroenterologist carefully feeds the endoscope down the esophagus and into the stomach and duodenum. A small camera mounted on the endoscope transmits a video image to a monitor, allowing close examination of the intestinal lining.

- An upper GI series examines the small intestine. During the procedure, the person will stand or sit in front of an x-ray machine and drink barium, a chalky liquid. Barium coats the small intestine, making signs of a blockage or other complications of gastric surgery show up more clearly on x rays.

Diagnosis of gastric varices is often made at the time of upper endoscopy.

The Sarin classification of gastric varices identifies four different anatomical types of gastric varices, which differ in terms of treatment modalities.

A diagnosis of gastric dilatation-volvulus is made by several factors. The breed and history will often give a significant suspicion of gastric dilatation-volvulus, and the physical exam will often reveal the telltale sign of a distended abdomen with abdominal tympany. Shock is diagnosed by the presence of pale mucous membranes with poor capillary refill, increased heart rate, and poor pulse quality. Radiographs (x-rays), usually taken after decompression of the stomach if the dog is unstable, will show a stomach distended with gas. The pylorus, which normally is ventral and to the right of the body of the stomach, will be cranial to the body of the stomach and left of the midline, often separated on the x-ray by soft tissue and giving the appearance of a separate gas filled pocket (double bubble sign).

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.

Younger people with ulcer-like symptoms are often treated with antacids or H2 antagonists before endoscopy is undertaken.

People who are taking nonsteroidal anti-inflammatories (NSAIDs) may also be prescribed a prostaglandin analogue (misoprostol) in order to help prevent peptic ulcers.

Little is known on the prognosis of achlorhydria, although there have been reports of an increased risk of gastric cancer.

A 2007 review article noted that non-"Helicobacter" bacterial species can be cultured from achlorhydric (pH > 4.0) stomachs, whereas normal stomach pH only permits the growth of "Helicobacter" species. Bacterial overgrowth may cause false positive H. Pylori test results due to the change in pH from urease activity.

Small bowel bacterial overgrowth is a chronic condition. Retreatment may be necessary once every 1–6 months. Prudent use of antibacterials now calls for an antibacterial stewardship policy to manage antibiotic resistance.

Although it would seem to be the better way to go in terms of management, there has been recent criticism on the need for such testing because of reliability issues. However, it must be stated that there are options such as the glucose breath test and jejunal aspiration the explanations of which are beyond the scope of this current article.

GAVE is usually diagnosed definitively by means of an endoscopic biopsy. The tell-tale watermelon stripes show up during the endoscopy.

Surgical exploration of the abdomen may be needed to diagnose some cases, especially if the liver or other organs are involved.

Proton pump inhibitors (such as omeprazole and lansoprazole) and histamine H2-receptor antagonists (such as famotidine and ranitidine) are used to slow acid secretion. Once gastric acid is suppressed, symptoms normally improve.

On x-rays, gas may be visible in the abdominal cavity. Gas is easily visualized on x-ray while the patient is in an upright position. The perforation can often be visualised using computed tomography. White blood cells are often elevated.

Gastric dilatation volvulus is an emergency medical condition: having the animal examined by a veterinarian is imperative. GDV can become fatal within a matter of minutes.

Treatment usually involves resuscitation with intravenous fluid therapy, usually a combination of isotonic fluids and hypertonic saline or a colloidal solution such as hetastarch, and emergency surgery. The stomach is initially decompressed by passing a stomach tube, or if that is not possible, trocars can be passed through the skin into the stomach to remove the gas, alternatively the trocars may be inserted directly into the stomach following anaesthesia in order to reduce the chances of infection. During surgery, the stomach is placed back into its correct position, the abdomen is examined for any devitalized tissue (especially the stomach and spleen). A partial gastrectomy may be necessary if there is any necrosis of the stomach wall.

It is important to differentiate DPI from small intestinal obstruction, since obstruction may require surgical intervention, but this can at times be difficult. Horses suffering from DPI usually have a higher protein concentration in their peritoneal fluid compared to horses with small intestinal obstruction, often without a concurrent increase in nucleated cell count. They usually have some relief and decrease in pain after gastric decompression, while horses with an obstruction often still act colicky after nasogastric intubation. Distention of the small intestine may be less than what is felt on rectal examination of horses with obstruction, especially after gastric decompression. Horses with DPJ usually produce larger volumes of reflux (usually greater than 48 liters in the first 24 hours) than those with obstruction, and are often pyretic (temperatures of 101.5–102.5) and have alterations in white blood cell levels, while those with obstructions usually have a normal or lower than normal temperature and normal leukocyte levels.

Ultrasound can also be helpful to distinguish DPJ from obstruction. Horses with small intestinal obstruction will usually have an intestinal diameter of −10 cm with a wall thickness of 3–5mm. Horses with proximal enteritis usually have an intestinal diameter that is narrower, but wall thickness is often greater than 6mm, containing a hyperechoic or anechoic fluid, with normal, increased, or decreased peristalsis. However, obstructions that have been present for some time may present with thickened walls and distention of the intestine.

DPJ can only be definitively diagnosed during surgery or at necropsy, when its gross appearance of the small intestine may be evaluated.

Gastroscopy, or endoscopic evaluation of the stomach, is useful in chronic cases of colic suspected to be caused by gastric ulcers, gastric impactions, and gastric masses. A 3-meter scope is required to visualize the stomach of most horses, and the horse must be fasted prior to scoping.

Antacids are a common treatment for mild to medium gastritis. When antacids do not provide enough relief, medications such as H blockers and proton-pump inhibitors that help reduce the amount of acid are often prescribed.

Cytoprotective agents are designed to help protect the tissues that line the stomach and small intestine. They include the medications sucralfate and misoprostol. If NSAIDs are being taken regularly, one of these medications to protect the stomach may also be taken. Another cytoprotective agent is bismuth subsalicylate.

Several regimens are used to treat "H. pylori" infection. Most use a combination of two antibiotics and a proton pump inhibitor. Sometimes bismuth is added to the regimen.