Gastroenteritis: Symptoms, Causes, Treatment and Diagnosis

Gastroenteritis: Symptoms, Causes, Treatment and Diagnosis

Gastroenteritis is very common. In the UK, around one in four people each year will have a gastroenteritis infection. Gastroenteritis is an contamination of your belly or bowels. You may also hear it referred to as a tummy...

What is gastroenteritis?

Gastroenteritis is an infectious illness of the intestine that may affect persons of all ages worldwide.

It usually causes vomiting or/and diarrhoea

which may be accompanied by fever, nausea, abdominal cramps, anorexia and myalgia. It is also known as stomach flue.This is because of inflammation of the lining of the intestine and stomach. This is also known as food poisoning as there are microorganisms present that produces a toxin in the gut because of which toxins may be absorbed.

Among healthy young adults, acute gastroenteritis is rarely fatal, but it includes medical and social costs. 

t is a likely diagnosis when the onset of gastroenteritis exhibits a strong temporal relationship to a particular meal. (refer to Diseases of the Gastrointestinal Tract)

What causes gastroenteritis?

There are a number of microorganisms that may cause this disease but it is mostly bacterial, viral and parasitic organisms.

The viruses involved are:

  • Rotaviruses
  • Astro virus
  • Toro virus
  • Norovirus
  • Picobirnaviruses
  • Norwalk viruses
  • Caliciviruses

The bacterias involved are:

  • Salmonella Typhi
  • Enterohaemorrhagic Escherichia coli
  • Campylobacter spp.
  • Vibrio
  • V.Cholerae
  • Listeria

Poor sanitation and inadequate personal hygiene are mainly responsible for the spread of these bacterial and viruses


• Toxin-induced

• Preformed toxins: Staphylococcus aureus, Bacillus cereus

• Enterotoxins produced in the intestine: Vibrio cholera, E. coli (enterotoxigenic, ETEC), Clostridium

Perfringens, Clostridium difficile

• Changes in mucosa

• Mucosa! alteration without invasion: Rotavirus, Norwalk agent

• Invasion of mucosa with destruction: Shigella, E. coli (enteroinvasive), Campylobacter, Yersinia enteroco- litica, Salmonella, Entamoeba histolytica, Bacillus anthracis


Allergic: Shellfish, strawberries

Non-allergic: Scrombrotoxin (fish), ciguatoxin (tropical fish), fungi

Ciguatera fish poisoning occurs after eating reef fish (tropical fish) contaminated with toxins such as ciguatoxin which originate from small marine organisms (dinoflagellates).

Dinoflagellates are ingested by herbivorous fish in which cigua­ toxin is concentrated as it passes up the food chain to large carnivorous fish and finally to humans. Besides features of acute gastroenteritis occurring within 1-3 hours, neurologic features also develop over next few hours and include par­ aesthesias, pain in teeth, metallic taste, blurred vision and cold allodynia (touching cold objects produces pain).

Scrombrotoxin (histamine) poisoning occurs due to ingestion of some fish which have high histidine content e.g. tuna, sardine etc. Histidine is converted into histamine if fish is stored improperly. Features include facial flushing, headache, palpitations, itching, blurred vision, abdominal cramps and diarrhoea. Occasionally, cardiac arrhythmia and hypotension may occur.

Difference between viral and bacterial  gastroenteritis

Characteristics of Gastroenteritis caused by virus

  • It is more common in winter seasons
  • The incubation period  is of 1-3 days
  • Fever is common with rotavirus
  • Vomiting is prominent and can only be a feature
  • Diarrhoea is common and non-bloody in most cases
  • For diagnosis, viral detectors can be used
  • In treatment – supportive therapy is used to maintain the fluid and electrolyte balance in the body .
  • Antibiotics are contraindicated.

Characteristics of bacterial gastroenteritis

  • More common in rainy or summer seasons
  • The incubation period is of  1-7 days
  • Fever is common with the inflammatory diarrhoea
  • Vomiting is common with bacteria-producing toxins.
  • Diarrhoea is prominent and occasionally bloody with agents causing inflammatory diarrhoea
  • For diagnosis – faecal examination is done for leukocytes and blood. Culture of stool specimen
  • can be done.
  • In treatment – Supportive therapy is adequate for most patients.
  • Antibiotic therapy is recommended in patients

How often people get gastroenteritis?

Nearly about 70% of the acute gastroenteritis in children is due to viruses, especially rotavirus and norovirus are more dominant. This disease is more common in children as compared to adults.

Bacterial gastroenteritis is only responsible for 10-20% of the infections.

Rotavirus and norovirus are the most common cause of the gastroenteritis and is associated with high mortality rate.


Rotavirus are a member of the family Reoviridae. Seven major groups of the rotavirus are present, gastroenteritis is mainly caused by group A and too a much lesser extent by group B and group C. Nearly all children are involved by rotavirus by 3-5 years.

Rotavirus infection can cause sever dehydration.

Astro virus 

This virus cam cause disease to all people including children and adults. Infection occurs around the summers. Transmission cam be through road faecal route or through the direct droplets.


 • Bacillary dysentery results from an acute infection of the intestinal tract by one of the three Shigella species-S. dysentria, S. jlexneri and S. sonnei.

• These organisms produce an endotoxin as well as an exotoxin (Shiga toxin). The exotoxin has enterotoxin activity causing intestinal secretion and cytotoxic properties directed against intestinal epithelial cells.

Clinical Features

• S. sonny produces only mild infection. S. jlexneri infection is usually more severe, while that due to S. dysenteriae may be fulminating and cause death within 48 hours.

• Fever and signs of systemic toxicity may be present in severe cases.

• Signs of dehydration and electrolyte disturbances are present in severe cases.

• The dysentery is mild to severe in intensity and is associated with tenses and colicky abdominal pain.

• The stools are small in quantity, and contain blood, mucus and purulent exudate with little faecal material.

• There may be tenderness over the colon elicited in the left iliac fossa.

• Bowel sounds are hyperactive.


• Rectal prolapse.

• Toxic megacolon.

• Colonic perforation.

• Bacteraemia.

• Meningismus, seizures.

• Transient peripheral neuropathy.

• Retire’s syndrome (reactive arthritis) with arthritis, conjunctivitis and urethritis may follow shigellosis.

• Haemolytic-uraemic syndrome, thrombotic • Bacillary dysentery results from an acute infection of the intestinal tract by one of the three Shigella species-S. dyseneria , S. jlexneri and S. sonnei.

How do microorganisms enter the healthy body?

  • Viruses are predominantly transmitted through the faecal-oral route, which means they may enter through the oral cavity as well as through the rectum.
  • It may also, be transmitted through air droplets from the infected person, that is by aerosolization.
  • Directly by person-to-person contact
  • Bacteria may also directly invade the mucosa of the small intestine.

How these organisms effect ? (pathophysiology)

  • Viruses get attached to the particular site or cell receptors in intestine .
  • These attachments of viruses lead to blunt lesions in the intestine which persists for few days.
  • As a result of these lesions there is less absorption of the food ( carbohydrate and fats)
  • This affects the motor neurons (nerves) present in the intestine causing delayed the response which may lead to nausea and vomiting, which is the typical sign of illness.
  • All this process causes dehydration in the body .

Signs and symptoms of gastroenteritis

• Food poisoning presents with vomiting, diarrhoea or both, usually within 48 hours of consumption of the contaminated food or drink. The stools may be bloody and there may be associated cramps abdominal pain and fever.

• Non infective causes and bacterial toxins that are preformed in the infected food produce symptoms within minutes or hours of a meal, whereas other conditions may not produce symptoms for up to 48 hours.

Usually,there is a history of simultaneous occurrence of symptoms in more than one member of a household or institution.

• Diagnosis is based on the identification of the specific pathogen by culture of the patient's stool, vomitus or blood or the contaminated food.

  • The incubation period (the period when the virus enters the body until it becomes symptomatic ) is of 24 hour.
  • Viruses can pass asymptotically or it can show symptoms as well as stay for a prolonged time in immunocompromised individuals.
  • The illness remains for 12 to 60 hours (1-4days) and are usually characterised by –
  •  Nausea
  • Vomiting
  • Abdominal cramps and
  • Diarrhoea (stools may be loose or watery without blood and mucus)
  • Bloating
  • Abdominal pain

As all this causes different degrees of dehydration in different people it may accompany symptoms due to level of dehydration such as:

  • Thirst
  • Headache
  • Altered skin
  • Dry mucosal membrane
  • Postural hypotension


The first basic diagnosis can be made by 

  1. Stool inspection for blood .
  2. Examination of ova, cyst and parasite.
  3. Stool culture for different viruses
  4. To check serum electrolytes which can indicate the degree of inflammation and dehydration.

Other lab diagnoses include 

PCR ( polymerase chain reaction)

s a method to amplify a minute amount of DNA within a few hours.

• The double-stranded DNA is denatured by heat into single-stranded DNA.

• DNA primers of interest are added along with the four basic deoxynucleotides and the solution is cooled. This results

in binding of DNA probes to their target DNA.

• DNA polymerase is used to extend the primers in opposite directions using target DNA as a template.

• This cycle is repeated several times that results in production of millions of copies of the original DNA.

• Used in medical and biological research laboratories for a variety of tasks, such as sequencing of genes, diagnosis of

hereditary diseases, identification of genetic fingerprints (used in forensics and paternity testing), detection ­

sis of infectious diseases and creation of transgenic organisms.

• In reverse transcriptase PCR (RT-PCR), RNA from the sample is converted to DNA using a retrovirus reverse transcriptase polymerase and the DNA is amplified by PCR.

• In real time PCR, the rate of DNA amplification is monitored as an indication of the initial concentration of sample DNA.

VLPs (virus-like particles)

Newer diagnostic techniques are considerably more technical sensitive than previous detectable methods, such as

  • Electron microscopy
  • Immune electron microscopy.


This disease is self-limited and oral rehydration therapy is generally adequate. If severe dehydration develops then intravenous (IV) fluid therapy is indicated.

No specific antiviral therapy is available.

Fluid replacement

Replacement of fluid loss in in diarrhoea illness is crucial and maybe life-saving.

Normal daily intake of fluid is usually 1-2 L, but with diarrhoea, it can result in substantial fluid loss; for example, 10-20 L of fluid may be lost in 24 hours due to cholera.

Along with fluid loss it also leads to the lose of electrolytes causing electrolyte imbalance in body.

ORS ( oral rehydration solution ) helps in this situation as it helps in rehydration as well as in maintaining the electrolyte balance in the body. ORS can be as effective just as intravenous replacement therapy in the management of diarrhoea.

Non-specific therapy includes oral or intravenous replacement of fluid and electrolyte deficits and codeine phosphate or loperamide for controlling diarrhoea (only if the patient does not have fever or blood in the stools). Loperarnide should be avoided in young children and elderly persons.

Antibiotics should not be given routinely, as they are usually ineffective and frequently exacerbate symptoms. However, antibiotic therapy is indicated in selected cases where the specific pathogen is isolated.

Proper food intake and balance diet should be taken


• Rectal prolapse.

• Toxic megacolon.

• Colonic perforation.

• Bacteraemia.

• Meningismus, seizures.

• Transient peripheral neuropathy.

• Reiter's syndrome (reactive arthritis) with arthritis, conjunctivitis and urethritis may follow shigellosis.

• Haemolytic-uraemic syndrome, thrombotic thrombocytopenic purpura.


  1. Control of contamination of food and water along with providing measures for clean drinking water and food.
  2. Appropriate disposal of human and animal sewage
  3. This application of the simple principle of food and hygiene can all limit gastroenteritis
  4. Practising good hand washing, as this may lead in a clean hands and free of virus. 

But the role of immunoprophylaxis is not clear in this disease, so the lack of immunity may also cause the same.

However, efforts can be made to develop a vaccine against viruses.