Diseases of the gastrointestinal diseases is known as gastrointestinal disease and it includes diseases of:

1. oesophagus
2. stomach
3. small intestine
4. large intestine 
5. rectum

and the accessory organs of digestion, the 
1. liver
2. gallbladder
3. pancreas.

Oesophageal diseases

Oesophageal diseases include a number of disorders affecting the oesophagus. The most common oesophageal disease is gastroesophageal reflux disease, which in chronic forms result in changes to the epithelium of the oesophagus, known as Barrett's oesophagus.

Acute disease of oesophagus include infections such as: 
1. oesophagitis,
2. rupture of veins such as oesophageal varices
3. Chronic diseases might include congenital diseases.

Gastric diseases

Gastric diseases are the diseases affecting the stomach.

1. Inflammation of the stomach by infection due to any cause is called gastritis, and when including other parts of the gastrointestinal tract called gastroenteritis.
2. Chronic gastritis is related to several diseases such as atrophic gastritis, pyloric stenosis, and gastric cancer.
3. Another common condition is gastric ulceration, peptic ulcers.
4. Peptic ulcers are most commonly caused by a bacterial infections, autoimmune, and physiological states.
5. Some common symptoms of stomach disorders are indigestion, vomiting, and in chronic disease, digestive problems leading to forms of malnutrition.

Intestinal diseases.

1. Inflammation of the intestines is called enter colitis. 
2. Intestinal disorders cause vomiting, diarrhoea or constipation, and altered stool, such as blood in stool.

Causes of gastrointestinal diseases

There are many causes of gastrointestinal diseases. Inflammation of the stomach and small intestine due to viral or bacterial infection from contaminated food is the major cause. Usually in rainy season food and water is contaminated and there are more chances of gastrointestinal diseases in rainy season. But its not that gastrointestinal diseases occurs only in rainy season it may occur anytime because other that contaminated food there are other causes of gastrointestinal diseases such as stress, change in routine, congenital disorders etc.

The most common disease caused by water and food contamination are diarrhoea, typhoid, dysentery cholera etc.
Salmonella bacteria is the cause of 1 to 5 million cases of diarrheal illness. Salmonella is a major cause of food poisoning, are usually found in raw chicken or eggs.
Shigella bacteria are highly contagious and they spread easily from one person to another. They cause ulcers that bleed. Shigella infections results in more than 160 million cases of diarrhoea each year.

E. coli bacteria are found in intestine of people and animals. It is a good bacteria but some strains release a toxin that can cause problems to little kids and older people. E. coli infections spread through contaminated water and food, such as unwashed fruits and vegetables that came into contact with animal manure.

Gastrointestinal diseases are very common and it should be treated on time. Therefore, as soon as you get a gastrointestinal disease you should consult a specialised gastroenterologist.

One should take proper precautions because the major cause of gastrointestinal diseases is poor sanitation, hygiene, contaminated water and food ingestion.

Precautions that should be taken are:

1. Wash your hands more often
2. Make sure that your kitchen counter and utensils are properly cleaned before cooking food.
3. Don’t eat left out food
4. Always consult a specialised gastroenterologist for treatment.

Author's Bio: 

Know more about gastric related disease and doctor to consult for the same on the below links :