There are many possible causes of constipation. It is important to find the cause and treat them specifically. Repeatedly taking laxatives may help but it does not treat the cause.
Your doctor will want to check for any anatomic causes, such as growths or areas of narrowing in the colon. Examination of the anus and rectum is usually the first step, since it is relatively simple and may show the cause of the problem. Examination of the intestine with either a colonoscopy or barium x-ray study may also be required. This is to look for conditions such as such as polyps, cancers, or diverticular disease, which may cause constipation. If this is found, then the underlying condition can be treated.
Other test may be needed to identify specific problems with the movement of your intestines. A "marker studies" in which the patient swallows a capsule containing markers that show up on x-rays taken several days later, provide clues to disorders in the movement of the intestines. Other physiologic tests check the function of the anus and rectum. These include testing the reflexes of anal muscles that control bowel movements using a small plastic catheter, or x-ray testing to evaluate function of the anus and rectum during defecation.
In many cases, no specific anatomic or functional causes are identified and the cause of constipation is said to be nonspecific.