Case scenario

A 47 year old man consults because he has had diarrhoea for the past 10 days. Three weeks ago he travelled to Bangkok for an academic convention. He now has occasional cramping abdominal pain and feels generally off colour; he has not lost weight and has not noticed blood or mucus in his stools. He has taken loperamide for the past few days, without much benefit.

The diagnostic dilemma

The diagnostic dilemma is to distinguish between diarrhoea due to short term, probably infective, causes and diarrhoea that represents an early symptom of a more serious gastrointestinal disorder. Acute diarrhoea is somewhat arbitrarily defined as diarrhoea for less than four weeks.1 It is said to affect almost every adult in the United Kingdom every year,2 though most people do not consult a doctor about it.3 4 Viruses are the most common infectious cause in the community, and Campylobacter (12%) and rotavirus (8%) are the organisms most commonly isolated among people who consult a general practitioner,5 though isolation rates of norovirus have increased recently.6 Possible non-infective causes include drugs, alcohol, and anxiety as well as more serious problems such as inflammatory bowel disease and bowel cancer.

In distinguishing between self limiting and more serious causes of acute diarrhoea, the doctor needs to know the patient’s background, including factors such as recent foreign travel; general health (comorbidities such as HIV infection, disorders such as hyperthyroidism and diabetes, and previous gastrointestinal surgery); “red flag” symptoms and signs, such as blood in the stool; recent hospital treatment or antibiotics; evidence of dehydration or intra-abdominal disease (a mass or marked abdominal tenderness, for example); …