Hello! Thank you for the query. IBS is not any specific disease. It is more a group of symptoms which reason can not be found (as present medicine still does not have many answers). So in other words IBS means We do not exactly know what is causing your symptoms . Colospa (Mebeverine) is a medicine which affect smooth muscles of gastrointestinal tract relaxing them without impeding bowels movements. Most of the abdominal pains are caused by muscles spasm, so you may find it effective with severe pain what does not mean that you have an IBS. Lower left abdominal pains is very often caused by diverticulitis (especially if you do have chronic constipation). It can also appear due to urinary tract infection, left ovarian cyst or infection, inguinal hernia. If all this diseases has been ruled out (with colonoscopy, abdominal ultrasound, transvaginal ultrasound, urine analysis and blood work) you may be suffering from IBS. IBS in some part of cases is caused by chronic bacterial infection, therefore Rifaximine treatment can be very helpful. Hope this will help. Regards.