Bloating, gas, diarrhea and constipation certainly can be caused by irritable bowel syndrome.
However, before attributing it to that, you may want to consider a flexible sigmoidoscopy or colonoscopy. This can evaluate for more serious diseases and causes, as well as monitoring the polyps. Any changes in bowel habits can certainly be due to anatomical changes within the colon.
An abdominal CT scan can be considered if the endoscopy is negative.
If all the tests remain negative, then treatment for IBS can be considered via increasing fiber intake as well as antispasmodic agents.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Kevin, M.D.
Medical Weblog:
kevinmd_b