Diarrhoea and Vomiting ; causes and treatment

Acute diarrhoea and vomiting

Acute diarrhoea, sometimes with vomiting, is an extremely common presenting problem, and may result from both infectious and noninfectious causes. Infectious diarrhoea is caused by transmission of viruses, bacteria or protozoa either by the faecal–oral route or via infected fomites, food or water. Psychological or physical stress may also precipitate diarrhoea. Occasionally, diarrhoea may be the presenting feature of another systemic illness, such as pneumonia.

Enterotoxic organisms, e.g. Bacillus cereus, Staph. aureus and Vibrio cholerae, produce vomiting and/or ‘secretory’ watery diarrhoea. Organisms that invade the mucosa, such as Shigella, Campylobacter and enterohaemorrhagic E. coli (EHEC), have longer incubation periods and may cause systemic upset and blood in the stool. summarises the causes of bloody diarrhoea.


Clinical assessment

History: Should include:

Duration and frequency of diarrhoea.

Presence of blood, abdominal pain and tenesmus.

Recent foods ingested (common associations are shown in. 

Other family members affected.

Causes of bloody diarrhoea


Campylobacter spp., Shigella dysentery, non-typhoidal salmonellae, enterohaemorrhagic or enteroinvasive E. coli, C. difficile, Vibrio parahaemolyticus, Entamoeba histolytica


• Diverticular disease, rectal or colonic malignancy, inflammatory bowel disease, bleeding haemorrhoids, anal fissure, ischaemic colitis, intussusception

Foods associated with infection, including gastroenteritis

Raw seafood: norovirus, Vibrio, hepatitis A

Raw eggs: Salmonella

Undercooked meat/poultry: Salmonella, Campylobacter, EHEC,C. perfringens

Unpasteurised milk or juice: Salmonella, Campylobacter, EHEC, Yersinia enterocolitica

Unpasteurised soft cheeses: Salmonella, Campylobacter, enterotoxigenic E. coli (ETEC), Y. enterocolitica, Listeria

Home-made canned foods: Clostridium botulinum

Raw hot dogs, pâté: Listeria Fever and bloody diarrhoea suggest an invasive, colitic, dysenteric process. Incubation < 18 hrs suggests a toxin-mediated food poisoning; > 5 days suggests protozoal or helminthic infection.


Assess degree of dehydration by skin turgor, pulse and BP measurement.

Measure urine output and ongoing stool losses.

Carry out regular full abdominal examination.


Stool microscopy (for cysts, ova and parasites), culture and C. difficile toxin assay.  

FBC, U&Es.  

Blood film for malaria if patient has been in an affected area.

Blood/urine culture and CXR: may reveal an underlying diagnosis.

Management of acute diarrhoea

Isolation: All patients with acute, potentially infective diarrhoea should be appropriately isolated to minimise person-to-person spread of infection. Fluid replacement: Replace established losses and ongoing losses, as well as normal daily requirements. This may be done with IV fluid or with oral rehydration solution (ORS). One sachet of commercial ORS made up to 200 mL is given for each diarrhoea stool

Antibiotics/antimicrobial therapy: Not generally used, except in severe cases (e.g. immunocompromise, comorbidity, systemic involvement). May precipitate haemolytic uraemic syndrome in EHEC infection.

Adjunctive antidiarrhoeal therapy: Anti-motility drugs are not generally recommended and may indeed prolong or worsen the course of an acute infective gastroenteritis.

Non-infectious food poisoning

Plant toxins: Those causing diarrhoea or vomiting occur in undercooked red kidney beans, in potatoes discoloured green by light and in many fungi. 

Chemical toxins: Originating in dinoflagellates and concentrated by shellfish or fish, these can cause gastrointestinal symptoms and paralysis. Scombrotoxic food poisoning results from eating contaminated tuna, mackerel or sardines.

Antimicrobial-associated diarrhoea: This is common in the elderly. Between 20 and 25% of cases are caused by C. difficile; if this toxin is detected, treatment with metronidazole or vancomycin is effective.

Infections acquired in the tropics

Fever in travellers recently returned from the tropics

Both tropical and non-tropical infection may present with fever after tropical travel. Frequent final diagnoses are:


Typhoid fever.  

Viral hepatitis. 

Dengue fever.

Travellers to West Africa may have viral haemorrhagic fevers (e.g. Marburg, Lassa or Ebola) while those in South-east Asia may have avian influenza (H5N1); all these require special isolation.

Clinical assessment


Countries and environments visited. 

Travel dates. 


ill people, animals, insect bites, freshwater swimming.



Sexual history. 

Malaria prophylaxis – what taken and

local resistance. 

Any local medicines/remedies taken. 


history – if the patient was vaccinated against yellow fever and hepatitis A and B, this virtually rules out these infections. Oral and injectable typhoid vaccinations are 70–90% effective. 

Examination: Careful, repeated examination is vital, paying particular attention to rashes or lesions, throat, eyes, nail beds, lymph nodes and abdomen .


Initial investigations in all settings should start with thick and thin blood films for malaria parasites, FBC, urinalysis and CXR if indicated. gives the diagnoses that should be considered in acute fever with no localising signs, grouped according to differential WCC.

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