Immediate treatment is the most important factor in a favorable prognosis. A delay in treatment greater than six hours or the presence of peritonitis, sepsis, hypotension, or disseminated intravascular coagulation are negative prognostic indicators.

Historically, GDV has held a guarded prognosis. Although "early studies showed mortality rates between 33% and 68% for dogs with GDV," studies from 2007 to 2012 "reported mortality rates between 10% and 26.8%". Mortality rates approach 10% to 40% even with treatment. A study determined that with prompt treatment and good preoperative stabilization of the patient, mortality is significantly lessened to 10% overall (in a referral setting). Negative prognostic indicators following surgical intervention include postoperative cardiac arrhythmia, splenectomy, or splenectomy with partial gastric resection. Interestingly, a longer time from presentation to surgery was associated with a lower mortality, presumably because these dogs had received more complete preoperative fluid resuscitation and were thus better cardiovascularly stabilized prior to the procedure.

The causes are divided into benign or malignant.

- Benign

- Peptic ulcer disease

- Infections, such as tuberculosis; and infiltrative diseases, such as amyloidosis.

- A rare cause of gastric outlet obstruction is blockage with a gallstone, also termed "Bouveret's syndrome".

- In children congenital pyloric stenosis / congenital hypertrophic pyloric stenosis may be a cause.

- A pancreatic pseudocyst can cause gastric compression.

- Pyloric mucosal diaphragm could be a rare cause.

- Malignant

- Tumours of the stomach, including adenocarcinoma (and its linitis plastica variant), lymphoma, and gastrointestinal stromal tumours

As a general rule, GDV is of greatest risk to deep-chested dogs. The five breeds at greatest risk are Great Danes, Weimaraners, St. Bernards, Gordon Setters, and Irish Setters. In fact, the lifetime risk for a Great Dane to develop GDV has been estimated to be close to 37 percent. Standard Poodles are also at risk for this health problem, as are Irish Wolfhound, Doberman Pinschers, Rottweilers, German Shorthaired Pointer, German Shepherds, Rhodesian Ridgebacks. Basset Hounds and Dachshunds have the greatest risk for dogs less than .

In a peptic ulcer it is believed to be a result of edema and scarring of the ulcer, followed by healing and fibrosis, which leads to obstruction of the gastroduodenal junction (usually an ulcer in the first part of the duodenum).

Incidence of hiatal hernias increases with age; approximately 60% of individuals aged 50 or older have a hiatal hernia. Of these, 9% are symptomatic, depending on the competence of the lower esophageal sphincter (LES). 95% of these are "sliding" hiatus hernias, in which the LES protrudes above the diaphragm along with the stomach, and only 5% are the "rolling" type (paraesophageal), in which the LES remains stationary, but the stomach protrudes above the diaphragm.

Hiatus hernia are most common in North America and Western Europe and rare in rural African communities. Some have proposed that insufficient dietary fiber and the use of a high sitting position for defecation may increase the risk.

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

Gastric volvulus of unknown cause comprises two thirds of cases and is presumably due to abnormal laxity of the gastrosplenic, gastroduodenal, gastrophrenic, and gastrohepatic ligaments. Type 1 gastric volvulus is more common in adults but has been reported in children.

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.

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.

Type 2 gastric volvulus is found in one third of patients and is usually associated with congenital or acquired abnormalities that result in abnormal mobility of the stomach.

Incidence of achalasia has risen to approximately 1.6 per 100,000 in some populations. Disease affects mostly adults between ages 30s and 50s.

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

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.

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.

It is a serious medical disorder and the mortality rate can be as high as 30%. The high mortality rate is likely a measure that this syndrome is seen in critically ill patients, rather than this syndrome being in itself lethal, although it can also present in otherwise healthy individuals (especially if the disorder was induced by pharmacologic agents). Drug induced megacolon (i.e. from Clozapine) has been associated with mortality as high as 27.5%.

Even after successful treatment of achalasia, swallowing may still deteriorate over time. The esophagus should be checked every year or two with a timed barium swallow because some may need pneumatic dilatations, a repeat myotomy, or even esophagectomy after many years. In addition, some physicians recommend pH testing and endoscopy to check for reflux damage, which may lead to a premalignant condition known as Barrett's esophagus or a stricture if untreated.

Horses may develop pharyngitis, laryngitis, or esophagitis secondary to indwelling nasogastric tube. Other complications include thrombophlebitis, laminitis (which subsequently reduces survival rate), and weight loss. Horses are also at increased risk of hepatic injury.

Survival rates for DPJ are 25–94%. Horses that survive the incident rarely have reoccurrence.

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.

Not all patients with Schatzki rings have symptoms; barium swallow tests of the esophagus sometimes show Schatzki rings in patients with no swallowing difficulties.

When Schatzki rings cause symptoms, they usually result in episodic difficulties with swallowing (dysphagia) solid foods, or a sensation that the food "sticks" while swallowing, especially if the food is not chewed thoroughly. Patients usually are able to regurgitate or force through the food material and resume eating. However, complete obstruction of the esophagus by a bolus of food (often called steakhouse syndrome) can occur. This can cause crushing chest pain and may need immediate treatment with endoscopy, which is the use of a specialized fibre-optic camera in order to remove the lodged food. After the obstruction is located, snares or forceps are inserted to pull the food out of the esophagus or to push it into the stomach. The latter is done with caution, usually when the anatomy of the structures around the obstruction is already known.

Ogilvie syndrome may occur after surgery, especially following coronary artery bypass surgery and total joint replacement. Drugs that disturb colonic motility (e.g., anticholinergics or opioid analgesics) contribute to the development of this condition.

Smoking increases the risk of developing gastric cancer significantly, from 40% increased risk for current smokers to 82% increase for heavy smokers. Gastric cancers due to smoking mostly occur in the upper part of the stomach near the esophagus. Some studies show increased risk with alcohol consumption as well.

Transient gastroparesis may arise in acute illness of any kind, as a consequence of certain cancer treatments or other drugs which affect digestive action, or due to abnormal eating patterns.

It is frequently caused by autonomic neuropathy. This may occur in people with type 1 or type 2 diabetes. In fact, diabetes mellitus has been named as the most common cause of gastroparesis, as high levels of blood glucose may effect chemical changes in the nerves. The vagus nerve becomes damaged by years of high blood glucose or insufficient transport of glucose into cells resulting in gastroparesis. Gastroparesis has also been associated with connective tissue diseases such as scleroderma and Ehlers–Danlos syndrome, and neurological conditions such as Parkinson's disease. It may also occur as part of a mitochondrial disease. Opioids and anticholinergic medications can cause medication-induced gastroparesis.

Chronic gastroparesis can be caused by other types of damage to the vagus nerve, such as abdominal surgery. Heavy cigarette smoking is also a plausible cause since smoking causes damage to the stomach lining.

Idiopathic gastroparesis (gastroparesis with no known cause) accounts for a third of all chronic cases; it is thought that many of these cases are due to an autoimmune response triggered by an acute viral infection. Gastroenteritis, mononucleosis, and other ailments have been anecdotally linked to the onset of the condition, but no systematic study has proven a link.

Gastroparesis sufferers are disproportionately female. One possible explanation for this finding is that women have an inherently slower stomach emptying time than men. A hormonal link has been suggested, as gastroparesis symptoms tend to worsen the week before menstruation when progesterone levels are highest. Neither theory has been proven definitively.

Gastroparesis can also be connected to hypochlorhydria and be caused by chloride, sodium and/or zinc deficiency, as these minerals are needed for the stomach to produce adequate levels of gastric acid (HCl) in order to properly empty itself of a meal.

Dietary factors are not proven causes, but some foods including smoked foods, salt and salt-rich foods, red meat, processed meat, pickled vegetables, and bracken are associated with a higher risk of stomach cancer. Nitrates and nitrites in cured meats can be converted by certain bacteria, including "H. pylori", into compounds that have been found to cause stomach cancer in animals.

Fresh fruit and vegetable intake, citrus fruit intake, and antioxidant intake are associated with a lower risk of stomach cancer. A Mediterranean diet is associated with lower rates of stomach cancer, as is regular aspirin use.

Obesity is a physical risk factor that has been found to increase the risk of gastric adenocarcinoma by contributing to the development of gastroesophageal reflux disease (GERD). The exact mechanism by which obesity causes GERD is not completely known. Studies hypothesize that increased dietary fat leading to increased pressure on the stomach and the lower esophageal sphincter, due to excess adipose tissue, could play a role, yet no statistically significant data has been collected. However, the risk of gastric cardia adenocarcinoma, with GERD present, has been found to increase more than 2 times for an obese person. There is a correlation between iodine deficiency and gastric cancer.

DPJ is most commonly seen in the Southeastern US, although cases have been reported throughout the United States and Canada, as well as sporadically in the United Kingdom and Europe. Horses in the Southeastern US tend to have a more severe form of the disease relative to other locations. Age, breed, and gender appear to have no effect on disease prevalence.