Enteritis is inflammation of the small intestine. It is most commonly caused by food or drink contaminated with pathogenic microbes, such as serratia, but may have other causes such as NSAIDs, radiation therapy as well as autoimmune conditions like Crohns disease and celiac disease. Symptoms include abdominal pain, cramping, diarrhea, dehydration, and fever. Related diseases of the gastrointestinal system include inflammation of the stomach and large intestine. Duodenitis, jejunitis and ileitis are subtypes of enteritis which are localised to a specific part of the small intestine. Inflammation of both the stomach and small intestine is referred to as gastroenteritis. Signs and symptoms
Signs and symptoms of enteritis are highly variable and vary based on the specific cause and other factors such as individual variance and stage of disease. Symptoms may include abdominal pain, cramping, diarrhea, dehydration, fever, nausea, vomiting and weight loss. Causes
Autoimmune
Crohns disease – also known as regional enteritis, it can occur along any surface of the gastrointestinal tract. In 40% of cases, it is limited to the small intestine.Coeliac disease – caused by an autoimmune reaction to gluten by genetically predisposed individuals.Eosinophilic enteropathy – a condition where eosinophils build up in the gastrointestinal tract and blood vessels, leading to polyp formation, necrosis, inflammation and ulcers. It is most commonly seen in patients with a history of atopy, however is overall relatively uncommon. Infectious enteritis
In Germany, 90% of cases of infectious enteritis are caused by four pathogens, Norovirus, Rotavirus, Campylobacter and Salmonella.
Other common causes of infectious enteritis include bacteria such as Shigella and E. coli, as well as viruses such as adenovirus, astrovirus and calicivirus. Other less common pathogens include Bacillus cereus, Clostridium perfringens, Clostridium difficile and Staphylococcus aureus.Campylobacter jejuni  is one of the most common sources of infectious enteritis, and the most common bacterial pathogen found in 2 year old and smaller children with diarrhoea. It has been linked to consumption of contaminated water and food, most commonly poultry and milk. The disease tends to be less severe in developing countries, due to the constant exposure which people have with the antigen in the environment, leading to early development of antibodies.Rotavirus is responsible for infecting 140 million people and causing 1 million deaths each year, mostly in children younger than 5 years. This makes it the most common cause of severe childhood diarrhoea and diarrhea-related deaths in the world. It selectively targets mature enterocytes in the small intestine, causing malabsorption, as well as inducing secretion of water. It has also been observed to cause villus ischemia, and increase intestinal motility. The net result of these changes is induced diarrhoea. Enteritis necroticans is an often fatal illness, caused by β-toxin of Clostridium perfringens. This causes inflammation and segments of necrosis throughout the gastrointestinal tract. It is most common in developing countries, however has also been documented in post-World War II Germany.