The final article in our series of abridged chapters from the recently updated Symptom Sorter, which gives a grassroots analysis of common presenting symptoms in primary care
The GP overview
This is a very common presentation and is usually caused by gastroenteritis or another acute infection. Less common is the subacute or prolonged case, where the differential is wider.
Differential diagnosis
Common
• Gastroenteritis.
• Other systemic infection (such as UTI, otitis media, pneumonia).
• Toddler’s diarrhoea.
• Medication side-effects (usually antibiotics).
• Cows’ milk protein intolerance (CMPI).
Occasional
• Lactose intolerance (typically following a bout of gastroenteritis in babies).
• Irritable bowel syndrome.
• Faecal impaction (causing overflow diarrhoea).
• Coeliac disease.
• Other infections such as giardia.
Rare
• Inflammatory bowel disease (IBD).
• Appendicitis (relatively common but in rare cases can present with diarrhoea).
• Intussusception.
• Cystic fibrosis.
Possible investigations
Likely
None.
Possible
Stool culture if diarrhoea persists more than a week, is bloody or there is recent foreign travel, urinalysis, MSU, FBC, CRP, ESR, anti-endomysial and anti-gliadin antibodies, faecal calprotectin.
Small print
Hospital tests might be necessary for cystic fibrosis, IBD and to confirm coeliac disease.
Top tips
• It is not unusual for the diarrhoea in gastroenteritis to take a couple of weeks to settle. Consider a stool specimen if it is not starting to improve after a week.
• Don’t overlook faecal impaction as a cause of overflow diarrhoea. The clues are soiling and preceding constipation.
• Lactose intolerance tends to be confused with CMPI. The former is less common, typically follows gastroenteritis and is usually shortlived.
• Undigested food (‘peas and carrots syndrome’) in the persistent loose stool of an otherwise well and thriving child is usually harmless toddler’s diarrhoea.
Red flags
• In the acute case – particularly in younger children with severe diarrhoea and vomiting – assess for dehydration. If the child is significantly dehydrated, admission is needed regardless of cause.
• Bloody diarrhoea raises the stakes. In the acute situation, this could be a more severe gastroenteritis or, especially in those under 12 months, intussusception. Prolonged cases might be CMPI or IBD.
• Very minor, transient weight loss is common during a bout of gastroenteritis. More prolonged weight loss with persistent diarrhoea should, on the other hand, prompt urgent referral.
• Appendicitis can cause diarrhoea. In such cases, the abdominal pain is usually more marked and constant than in a typical gastroenteritis, where it is typically mild (and therefore not the presenting complaint) and intermittent.
Dr Keith Hopcroft is Pulse’s clinical adviser and a GP in Basildon, Essex
