Introduction

A 35 year old woman with longstanding “loose bowels” reports an increasing incidence over two years of painful abdominal cramps and “rumblings,” with frequent loose stools and occasional leakage. Her work is stressful, and she worries that her bowel problems may affect her job performance.

What issues you should cover

Characteristics—Irritable bowel syndrome consists of abdominal pain and intermittent diarrhoea, constipation, or bloating. Possible contributing factors include stress or anxiety, visceral hypersensitivity, altered bowel motility, neurotransmitter imbalances, and inflammation. No single mechanism explains all cases, and no specific dietary causes are known. Symptoms usually begin before the age of 50, and up to 20% of the population may be affected.

Diagnosis—Differential diagnoses include inflammatory bowel disease, colorectal polyps or cancers, malabsorption (lactose intolerance or coeliac disease), infectious diarrhoea, and thyroid dysfunction. Although irritable bowel syndrome is often considered a diagnosis of exclusion, validated criteria allow positive diagnosis without extensive testing. The Manning criteria (see box) have been studied the most, and the presence of three of the six criteria is 66% to 90% sensitive and 61% to 93% specific for a diagnosis if no red flag signs are present. Although many doctors usually obtain a full blood count, electrolyte and thyroid stimulating hormone concentrations, and erythrocyte sedimentation rate, evidence indicates that only the full blood count is always needed. Determining whether the predominant symptoms are diarrhoea, pain, or constipation can help guide management.

Management—Reassurance and explanation are important, and some experts suggest reducing dietary fat, alcohol, and caffeine intake. Evidence supports increased dietary fibre for constipation, drugs for specific symptoms, and multicomponent behaviour therapy, including education, coping strategies, relaxation, and cognitive behaviour therapy. Comorbid psychiatric illness should be treated.

What you should do

• Does she meet the Manning criteria? (What are the nature and duration of abdominal complaints? Is there pain? Is it relieved with defecation or associated with changes in stool form or frequency? Is there faecal urgency or incontinence or a feeling of incomplete evacuation?) Ask about weight loss, intestinal bleeding, and fever. Ask about dietary fibre and food intolerances and about any family history of intestinal disease or malignancy. Ask about work or family stress, any history of abuse, depression, or anxiety, and the effect of symptoms on her daily life.

• Check whether she seems to be in good health and whether she has lost any weight. Perform abdominal and rectal examinations. A full blood count will rule out anaemia. Further testing at this point is probably unnecessary for patients aged under 50 who meet the Manning criteria and have no red flag signs.

• Explain the syndrome and reassure her that it doesn't represent serious disease or a greater risk of malignancy. Consider asking her to reduce dietary fat, alcohol, and caffeine and other dietary triggers that aggravate symptoms. Evidence supports treatment for specific predominant symptoms: bulking agents (wheat bran, psyllium) for constipation, loperamide for diarrhoea (initially 2 mg four times daily as needed), and tricyclic antidepressants for pain (starting with scheduled amitriptyline 25 mg at bedtime). The risk of severe side effects make the two new serotonergic drugs for the syndrome (alosetron and tegaserod) inappropriate for initial management. Explore life stresses that trigger symptoms, and consider relaxation or cognitive therapy.

Self help websites for patients are listed on bmj.com

The series is edited by general practitioners Ann McPherson and Deborah Waller (ann.mcpherson{at}dphpc.ox.ac.uk)

The BMJ welcomes contributions from general practitioners to the series