COMMON MEDICAL PRESENTATIONS MEDICINE 37:1 23 © 2008 Published by Elsevier Ltd. Diarrhoea Kinesh Patel Andrew V Thillainayagam Abstract Disturbances in bowel habit are frequent occurrences in both the devel- oped and developing world: their onset often prompts patients to seek medical attention. The causes of diarrhoea are myriad, ranging from the benign and self-limiting to the life-threatening. A careful history and examination are vital when managing patients presenting with diarrhoea. Further testing, which is often invasive and uncomfortable, should be reserved for those patients with worrying clinical features. Treatment of acute diarrhoea is often supportive; for those with chronic symptoms, treatment is usually aimed at the underlying cause. Keywords diarrhoea; gastroenteritis; infammatory bowel disease Diarrhoea is the most common illness in the UK after the com- mon cold; acute diarrhoeal illnesses account for about 10% of all visits to general practitioners and incur substantial time lost from school and work. Diarrhoea in vulnerable patients is a frequent cause of hospital admission. Worldwide, diarrhoeal diseases are second only to cardiovascular diseases as a cause of death. Diarrhoea is a complex, multifactorial entity with many causes. Many diarrhoeal illnesses are acute, short-lived and self-limiting: individuals usually do not seek medical advice but treat them- selves using over-the-counter remedies, by dietary modifcation or by doing nothing. Medical help is usually sought when diar- rhoea is more severe, is accompanied by fever or rectal bleeding, or results in prostration. There are several diagnostic tests. Many are expensive, time- consuming and invasive, so a systematic approach is essential to make an accurate diagnosis without subjecting the patient to unnecessary investigations. Definition Diarrhoea is defned as an decrease in consistency or increase in liquidity of stool. Acute diarrhoea is usually defned as diarrhoea Kinesh Patel MRCP is Specialist Registrar in Gastroenterology in the North West Thames Region, London, UK. Competing interests: none declared. Andrew V Thillainayagam MD FRCP is Consultant Physician at Hammersmith Hospital, Imperial College Healthcare Trust and Honorary Senior Lecturer in Medicine at Imperial College School of Science, Technology and Medicine, London, UK. Competing interests: none declared. lasting for up to 3 weeks; chronic diarrhoea is any diarrhoeal ill- ness that lasts longer. Clinical approach to diarrhoea It is useful to classify diarrhoeal illnesses to limit the potential causes and reduce the number of tests. There are many ways to classify diarrhoea, for example: • duration of diarrhoeal illness (acute versus chronic) • risk group (travellers to developing countries, patients with AIDS, hospital in-patients) • specifc features of the diarrhoea (bloody, fatty, watery) • pathophysiological category (osmotic, secretory, infamma- tory, dysmotility). Initially, the frst two classifcations are the most practi- cal and clinically useful because they require only a detailed history. Later, as fndings emerge from the physical exami- nation and more specifc investigations, other means of classifcation can be used to narrow the number of possible diagnoses. History The cornerstone of diagnosis in diarrhoea is a detailed history (Table 1). It is vital to determine what the patient means by ‘diarrhoea’. • High stool volumes (>1000 ml/day), unaffected by fasting, suggest a predominantly secretory process. • Moderate stool volumes which improve on fasting indicate a predominantly osmotic process. • Passage of low volumes (<500 ml) of loose stools suggests gut motility disturbance. • Bloody diarrhoea and abdominal pain suggest an infamma- tory process. • Proctitis is suggested by a frequent urge to defecate, particu- larly if the stool contains blood or mucus. • Steatorrhoea is the passage of bulky, greasy, foul-smelling stool. Mild or moderate malabsorption may become apparent only when complications follow vitamin or metabolite mal- absorption, resulting in anaemia, osteomalacia, neurological signs, etc. • Nocturnal diarrhoea, particularly with faecal incontinence, points towards organic disease (e.g. autonomic neuropathy) because it is uncommon in functional disorders. • Diabetes or scleroderma may indicate dysmotility or bacterial overgrowth. • Previous abdominal surgery (e.g. ileal resection, vagotomy, antrectomy, cholecystectomy) raises the possibility of iatrogenic diarrhoea. • A family history of diarrhoeal disease is uncommon, but can occur with coeliac disease, infammatory bowel disease (IBD) or multiple endocrine neoplasia syndromes. • The infuence of psychological stress should be explored sensitively: modest diarrhoea made worse by stress, alternating with constipation and associated with abdominal cramps or pain and bloating is typical of irritable bowel syndrome (IBS); stool weight is seldom increased in these patients. However, diar- rhoea as a lone entity can only rarely be attributed to functional bowel disease.