A distressing dysfunction of the intestines, in which there's both overactivity of the involuntary contractions of the intestines' muscular wall and increased pain signals coming from those contractions. Treatment is based on decreasing the contractions (with a diet high in fibre, sometimes with antispasmodic drugs) and attempting to reduce the action of the pain-carrying nerves, both by sedating them (this means general sedation too, so it's often not very acceptable) and by re-educating them to be less sensitive. Treatment is time consuming and, ultimately, not always satisfactory. The symptoms of the irritable bowel syndrome are often confused with those of endometriosis; they are sometimes made worse with, and at the time of, premenstrual tension, or, in my experience of patients with it, by performance of a laparoscopy. Typically (but not always), there is an alternating tendency towards diarrhea or constipation; sometimes there is nausea with the spasms.