Irritable bowel syndrome and related disorders of gut-brain interaction.

Irritable bowel syndrome, chronic constipation, and functional diarrhoea are disorders of gut-brain interaction, the symptoms of which include abnormal stool consistency or frequency accompanied by varying degrees of abdominal pain, discomfort, bloating, or distension. These conditions affect 20% of the global population with a relapsing and remitting course. Risk factors include female sex, younger age, a history of common mental disorders, and acute enteric infection. The pathophysiology of irritable bowel syndrome, chronic constipation, and functional diarrhoea remain incompletely understood, but are thought to be secondary to aberrant interactions throughout the gut-brain axis, resulting in disordered gut motility and visceral hypersensitivity. These conditions are diagnosed with a combination of clinical history, absence of alarm symptoms-such as weight loss or rectal bleeding-and targeted investigations. An empathetic management approach improves quality of life and symptoms, reduces health-care use, and enhances treatment adherence. Mainstays of treatment include education, dietary and lifestyle advice, modifying fibre intake, and drugs directed towards predominant symptoms. For severe symptoms, other treatments include specific medical devices, biofeedback, or psychological therapies. However, the effectiveness of most treatments is modest and there is an ongoing need to expand available treatments for bowel disorders, with several novel drugs currently in development.