Aims of assessment and differential diagnosis of gastroenteritis
The aim of assessing patients who present with gastroenteritis symptoms (diarrhoea, which may be accompanied by fever or vomiting) is to identify:
- the likely cause, focusing on excluding life-threatening conditions or conditions requiring specific medical or surgical interventions (see Examples of red flags for potentially life-threatening differential diagnoses of acute gastroenteritis). Only perform faecal testing if the results will alter management (see Faecal testing in acute infectious diarrhoea)Riddle, 2016
- complications or risk for complications, including:
- dehydration—see Assessing adults for dehydration and Assessing children for dehydration
- electrolyte imbalance
- perianal excoriation or skin breakdown
- medication-related complications—see Acute gastroenteritis and regular medications
- complications specific to the cause of acute gastroenteritis (eg haemolytic uraemic syndrome caused by Escherichia coli or Salmonella enteritis, pyogenic arthritis caused by Salmonella enteritis, Guillain-Barré syndrome caused by Campylobacter enteritis)Ternhag, 2008
- complications seen in older or frail patients (eg falls, pressure injuries, destabilisation of chronic disease, delirium)
- public health implications (to determine whether faecal testing or notification of the local public health authority is necessary1); for example, in an outbreak or if the patient:
- is in a residential aged-care facility
- is a food handler
- attends or works at a childcare centre or school
- availability of social support.
Consider additional investigations or referral to a relevant specialist if the patient has any of the red flags or findings listed in Examples of red flags for potentially life-threatening differential diagnoses of acute gastroenteritis.
|
Red flag |
Potential cause |
|---|---|
|
Patient history | |
|
associated respiratory symptoms [NB1] |
coronavirus disease (COVID-19)—gastrointestinal symptoms may precede respiratory symptoms atypical pneumonia anaphylaxis leptospirosis |
|
severe abdominal pain |
cause requiring surgical intervention (eg appendicitis, mesenteric ischaemia, perforated viscus, bowel obstruction)—more likely in older patients sepsis or septic shock |
|
upper gastrointestinal bleed (melaena or haematemesis) |
Mallory-Weiss tear varices peptic ulcer |
|
lower gastrointestinal bleed (bright red rectal bleeding) |
bowel cancer diverticulitis ischaemic gut inflammatory bowel disease or colitis |
|
onset of diarrhoea after exposure to an allergen |
anaphylaxis |
|
unintentional weight loss |
thyrotoxicosis bowel cancer inflammatory bowel disease |
|
vomiting without diarrhoea |
urinary tract infection increased intracranial pressure bowel obstruction cause requiring surgical intervention (eg appendicitis, mesenteric ischaemia, perforated viscus, bowel obstruction) poisoning |
|
recent fish ingestion |
ingestion of reef fish and associated neurological symptoms (eg ciguatera fish poisoning) ingestion of fish in Scombroidae family (eg mackerel, bonito) and associated facial flushing (scombroid poisoning) |
|
recent antibiotic use or recent hospitalisation |
Clostridioides difficile (formerly known as Clostridium difficile) infection |
|
immunosuppression [NB2] |
consider surgical causes (immunosuppression may reduce presence of classical clinical signs) risk for cytomegalovirus (CMV) or parasitic (eg Cryptosporidium species, Cystoisospora [Isospora] belli, microsporidia) infection graft-versus-host disease (GVHD) |
|
recent travel [NB2] |
malaria dengue fever hepatitis A hepatitis E |
|
pregnancy |
Listeria monocytogenes infection eclampsia |
|
history of ulcerative colitis or Crohn disease |
exacerbations of inflammatory bowel disease may present with diarrhoea |
|
history of previous abdominal surgery |
partial small bowel obstruction |
|
medications |
adverse effect of chemotherapy, antibiotics, laxatives toxicity or overdose of lithium, iron, colchicine, organophosphate insecticides withdrawal (eg from opioids) |
|
family history |
bowel cancer inflammatory bowel disease |
|
sexual history, particularly if new partner |
human immunodeficiency virus (HIV) infection syphilis gonorrhoea chlamydia |
|
Physical examination | |
|
haemodynamic compromise or organ dysfunction |
sepsis or septic shock (eg caused by Salmonella species, Escherichia coli, Neisseria meningitidis) toxic shock syndrome gastrointestinal haemorrhage (eg variceal bleed) toxidrome (eg iron overdose) |
|
altered conscious state |
increased intracranial pressure sepsis with secondary hypotension meningitis encephalitis |
|
abdominal guarding, rebound tenderness, rigidity or mass |
cause requiring surgical intervention (eg appendicitis, mesenteric ischaemia, perforated viscus, bowel obstruction) |
|
significant abdominal distention |
subacute bowel obstruction (if vomiting and diarrhoea are present) |
|
bilious vomiting |
bowel obstruction |
|
rash |
Neisseria meningitidis infection, if nonblanching or purpuric rash toxic shock syndrome Kawasaki disease viral illnesses (eg HIV infection, measles) atypical pneumonia |
|
Note:
NB1: Children with acute gastroenteritis may have concomitant adenovirus or respiratory syncytial virus (RSV) causing the associated respiratory symptoms. NB2: For patients who are immunocompromised or recent travellers, consider empirical antibiotic therapy; see the Antibiotic guidelines. | |