Diarrhea and vomiting

What is gastroenteritis?

Strictly speaking the word "gastroenteritis" means inflammation of the stomach and bowel. Inflammation can be caused by a number of diseases including infection. Doctors tend to use the term gastroenteritis to mean an infection causing inflammation of the lining of the gut resulting in diarrhea and vomiting. It can affect both adults and children although it is most common in children, especially those between the ages of 6 and 24 months.

What causes it?

Many types of infection can cause gastroenteritis including viruses, bacteria and parasites. The most common type of infections to cause gastroenteritis are viruses that are passed from person to person either in the air or by transmission on the hand to the mouth. There is one particular virus called rotavirus that is responsible for outbreaks of diarrhea in children usually under the age of 5. It tends to cause a more severe type of diarrhea than other kinds of viral gastroenteritis and it often lasts longer than the usual 2-3 days. Outbreaks of rotavirus infection tend to be seasonal and are thought to be transmitted by airborne spread from one child to another.

Diarrhea and vomiting can also be caused by the so-called "food poisoning" germs such as the bacteria Campylobacter, Salmonella or Shigella amongst others. These are picked up from food contaminated with these organisms which enters the gut in the food and then causes inflammation, spasm of the intestinal muscles and other symptoms as described below.

Some types of gastroenteritis are caused by parasites such as one called Giardia and another called Amoeba both of which are usually contracted by eating contaminated food or drinking unsterile water (often abroad).

What are the symptoms?

The main symptoms of gastroenteritis are diarrhea and/ or vomiting. How much diarrhea or vomiting each sufferer experiences varies from person to person. It also alters according to the age of the individual and which germ is the cause of the illness. However, in addition to the diarrhea and vomiting some infections can cause other symptoms such as stomach cramps, a fever, blood in the motions and a general feeling of illness. As a general rule simple viral gastroenteritis tends to cause diarrhea and vomiting without the other symptoms. Food poisoning infections (from bacteria and parasites) often lead to more severe symptoms such as stomach cramps and the passage of blood from the rectum.

If the diarrhea and vomiting are severe and/or prolonged, symptoms of dehydration may set in. In an adult this shows itself as a dramatic reduction in the production of urine associated with a significant feeling of thirst, general lethargy, a dryness of the tongue and loss of elasticity of the skin. In babies and children dehydration shows itself in a similar way to adults except babies may have a sunken fontanelle (soft spot on the top of the head). Children sometimes become sunken-eyed when significantly dehydrated. As a general rule the younger the child the more quickly they are likely to become dehydrated because their fluid reserves are less than an adults so medical advice should be sought early if dehydration is suspected.

How is infection caught?

The different types of infection are caught in different ways. Bottle fed babies can develop diarrhea and vomiting by picking up a germ from an unsterile teat or milk that has not been properly sterilised. As children reach an age where they start to mix with other people they may then contract a viral gastroenteritis from another child. Transmission from person to person remains the most common method of transmission of the illness either by airborne spread or what is called the "faeco-oral route" i.e. spread from unclean hands to mouth.

The other frequent method of contracting diarrhea and vomiting is due to foreign travel. Exotic locations for holidays are becoming more frequent resulting in the number of people returning from abroad with diarrhea doubling in the past decade. It has been estimated that about 18 million adults travel abroad each year and of these 39% develop diarrhea whilst they are away. The diarrhea is generally caused either by viruses or bacteria new to the body's defences (so-called "traveller's diarrhea") or by food poisoning germs such as Campylobacter mentioned above. The risk of gastroenteritis obviously varies according to the part of the world being visited; Northern Europe tends to be low risk whereas the risk increases to about 40% in areas such as Central America.

How is it diagnosed?

Diarrhea and vomiting caused by gastroenteritis is such a common problem in both adults and children that most cases are diagnosed by the family doctor purely on the history (symptoms) of the illness and an examination of the patient. However, if the symptoms are severe or lasting longer than the usual few days the doctor may organise the sending of a stool sample from the individual to the local hospital laboratory. There the stool is examined under the microscope for evidence of parasites of certain food poisoning organisms. It is then cultured on a culture plate for any type of gastroenteritis infection. If the patient is a child it may also be tested for rotavirus as mentioned above.

The doctor will also assess the patient to see how dehydrated they are in case hospital admission is required for rehydration.

How is it treated?

The majority of cases of diarrhea and vomiting can be successfully treated by encouraging the sufferer to drink small amounts of fluid frequently. The type of fluid is generally not important although it is usually best to stick to water or juice and on the whole milk is not recommended (although see below for advice in small babies). However, special rehydration preparations exist which are available over the counter at chemists and you should seek the advice of the pharmacist. These are sachets containing a small amount of sugar and a mixture of salts and minerals. They are made up with water into a rehydration solution to replace the salts and minerals lost in the diarrhea and vomit. Although these are very useful they are only important in the more severe cases. The most important thing is to replace any fluid loss.

Resting the stomach by stopping food for about 24 hours is said to help to stop any vomiting or diarrhea, but there is little published evidence for this. However, prolonged fasting, especially in children, can become unhelpful since hunger itself can begin to make the individual feel unwell. A good guide is to feed them if they are hungry and not if they are not hungry. In other words, trust the stomach itself to know best. Small babies who are being mainly bottle fed can be tried on what is called half-strength or quarter-strength milk. This means making up the milk with the same amount of water as normal but with only a half or a quarter the number of "scoops" of milk powder in the bottle. This has the effect of resting the stomach but still providing some substance. As the baby gets better the milk can be made more concentrated until they are back onto full strength milk. If even quarter-strength milk is vomited back than 12 or 24 hours of water or juice alone can be helpful in settling any vomiting before gradually returning to full strength. In very young babies or if any problems arise medical advice should be sought.

Drug and other treatment: Occasionally antibiotic treatment may be prescribed by the doctor if the type of infection causing the illness is thought to require it. For instance some types of food poisoning bacteria may need treatment with antibiotics. In most cases of gastroenteritis antibiotics are very unlikely to help and may even lead to unwanted side effects. Anti-diarrhea medication may be helpful to treat the symptoms of diarrhea in adults. Similar medication is not usually recommended in children because it may conceal the fact that the child is still unwell and may still be becoming dehydrated. Similarly, anti-diarrhea medication may cause problems in adults with severe diarrhea where there are other symptoms such as severe abdominal pain or blood in the motions in which case medical advice should be obtained.

Finally, if the patient is significantly dehydrated the doctor may think it best to admit them to hospital for intravenous rehydration where fluid is replaced via a "drip" i.e. a tube leading into a vein in the arm. This treatment usually works extremely well and often the sufferer is discharged from hospital within a day or two depending on their progress.

What are the other causes?

There are many causes of diarrhea and vomiting in adults and children; far to numerous to mention in this factsheet, but gastroenteritis is by far the most common cause of short-lasting diarrhea and vomiting. However, if other symptoms exist or the vomiting and/or diarrhea persist then a medical opinion should be obtained to establish a diagnosis.

How can it be prevented?

It is not always possible to prevent gastroenteritis because it is so easily spread from one person to another, especially amongst children. However, many cases can be prevented by practising good general hygiene i.e. washing after going to the toilet and before and during food preparation. For those people travelling abroad it is particularly important for them to be careful what they eat and drink. In high risk areas only bottled water should be drunk (and only ice made from bottled water) and food should only be eaten when prepared by the person themselves or by a reputable kitchen. Those in the catering trade should stay off work if they develop diarrhea and vomiting. They should only return to work once they have provided a normal stool result from the laboratory or on advice of their doctor.

In future it may be possible to vaccinate against certain types of gastroenteritis. For instance, dysentery (caused by an organism called Shigella) may in future be preventable with a vaccine, as may Cholera.

Last updated 10 May 2016