Spastic colon is the older term for irritable bowel syndrome, the common functional disorder of the gut. Sufferers endure abdominal pain, bloating, and erratic bowel habits, diarrhoea, constipation, or both, without any visible disease on investigation. The name reflected an early theory of colonic spasm; modern understanding points to disturbed gut-brain communication, visceral hypersensitivity, and altered microbiota. There is no cure, but management helps: dietary approaches including the low-FODMAP diet, stress reduction, exercise, and targeted medicines for pain, diarrhoea, or constipation. It is remarkably common, affecting perhaps one person in ten, and though not dangerous, its impact on daily life and work is substantial.