Constipation, Colonic Inertia, and Colonic Marker Studies
Constipation is a common symptom. Treatment for constipation often includes lifestyle modifications such as increasing fluid intake, consuming more fiber, and exercising regularly.
At times, the symptom of constipation can represent serious medical illnesses such as hypothyroidism or diabetes. Structural abnormalities of the colon, like colonic strictures or other diseases of the colon or rectum, may also cause constipation. That is why it is advisable to report constipation to your physician if it is persistent or difficult to manage.
Some individuals who have constipation have a disorder involving the nerves and muscles that control the process of defecation. Abnormalities that affect the pelvic muscles, spinal nerves, and the muscles of the anorectal region may result in the development of constipation. Conditions of this type are called defecation disorders. They are characterized by straining and incomplete rectal emptying.
Some people have constipation because of abnormal nerves and muscles of the colon itself. In these individuals, movement of material within the colon is markedly delayed. People with delayed colonic action (medically termed colonic inertia) have difficulty with moving stool through the colon.
In colonic inertia, stool may remain stored in portions of the colon and not progress adequately to the part of the colon (rectosigmoid) responsible for the propulsion and transfer of stool out of the body – the processes involved in defecation.
There are a variety of conditions that may cause slowing of colonic action. Medications such as some antihypertensives, pain relievers containing opioids, antidepressants, antipsychotics, and anticholinergics may all slow colonic action.
Hypothyroidism, diabetes, and some rheumatologic conditions may also decrease the function of the nerves and muscles within the colon and produce severe constipation.
Finally, there are some individuals that develop colonic inertia without an identifiable cause. This condition is termed idiopathic. It is seen most commonly in young women.
The symptoms of colonic inertia include long delays in the passage of stool accompanied by lack of urgency to move the bowels. Individuals with colonic inertia often do not pass a stool for 7–10 days at a time. Sometimes colonic inertia is accompanied by abnormalities in motility of the upper intestine including delayed emptying of the stomach and small intestinal pseudo-obstruction (a disorder that causes symptoms of blockage, but no actual blockage).
Because there are a large number of potential causes for the symptoms of constipation, your physician will want to review the medicines you are taking and may perform tests looking for disease or for abnormalities of the colon. Finally, you may have testing of the anorectal function to determine if a disorder of this region is present.
Colonic Marker/Transit Studies
Your physician may also have you undergo a colonic marker study, the most common clinical method of examining the rate of colonic movement. This simple test measures the movement of substances that enter and leave the colon over time. The time required to excrete these substances is called colonic transit.
To perform a marker test, a capsule containing a number of tiny rings (usually 24) is ingested by mouth. These rings have been specially treated so that they are clearly visible on an abdominal x-ray. Following ingestion, the capsule dissolves and the rings are released into the small and large intestines. After 12 hours, the rings are usually all present in the colon.
When an x-ray is obtained after 24 hours or longer, the number of rings present in the colon can be counted. Most clinicians take an x-ray 3 and 5 days after ingestion of the capsule. Alternately, x-rays can be performed on a daily basis until all of the rings have been excreted. At day 5, the presence of fewer than 20% of the ingested rings suggests normal colonic transit. If more than 20% of the rings are counted on the x-ray, delayed colonic transit is present.
If colonic transit time is normal, and medications or other medical disorders ruled out, treatment may include:
- Increasing water and fiber intake
- Following a bowel retraining program (regular and unhurried routine for having bowel movements)
- Getting adequate exercise
If anorectal dysfunction is a cause, biofeedback therapy can help retrain muscles to facilitate release of bowel contents and relieve symptoms.
What should be done if the marker study at day 5 shows an abnormality? Since a variety of causes may result in the development of delayed colonic transit, further evaluation should be done to rule out diseases within the colon, medical disorders, or causes related to medications.
Additionally, it is often useful to determine whether a defecation disorder involving the pelvic musculature or abnormality of the anorectal region is present. If the only abnormality found after an evaluation is performed is delayed colonic transit, the diagnosis of colonic inertia is made.
Idiopathic Colonic Inertia
Idiopathic colonic inertia is a disorder that most commonly affects females. It often begins at a young age (between ages 20–30). This condition can result in severe and stubborn constipation.
It is not uncommon for individuals with colonic inertia to begin to use stimulant laxatives as a treatment. Most, but not all physicians believe that use of stimulant laxatives on a long-term (chronic) basis can result in additional damage to the nerves and muscles of the lower intestine. It is important for a patient or physician to explore the use of other means to treat constipation.
If dietary changes fail to bring relief, medicines may be an appropriate next step. In addition to traditional laxatives, new prescription agents exist for constipation such as linaclotide (Linzess) and lubiprostone (Amitiza). Whether over-the-counter or by prescription, consultation with a physician is advised before long-term or chronic use of medications.
Biofeedback is a painless therapy that uses special equipment to help a person sense nerve or muscle functions we are not normally aware of. For example, a person could learn to relax pelvic floor and anal sphincter muscles as needed for a bowel movement.
In constipated patients, biofeedback techniques have generally been used to assist patients having spasms of pelvic muscles during defecation. In some of these conditions, such as failure of pelvic floor muscles to relax (pelvic floor dyssynergia), people often have a successful response to biofeedback therapy. Some patients with colonic inertia also may improve with biofeedback therapy.
Surgical techniques may be effective in some patients who have colonic inertia. The surgery for this condition involves the removal of the majority of the colon with reconnection of the small intestine to the rectum. Careful consideration and selection is extremely important to determine which patients will most likely benefit from surgery for chronic constipation, and which will not.
Chronic constipation is a common GI problem. It is a symptom, not a disease. It is important to see a physician to determine the cause of the symptom. This is especially important if constipation is accompanied by pain, bleeding, or a recent change in bowel habits.
Discuss the use of any medications with your physician to see if they may be contributing to your symptoms. Once the cause is accurately determined, the most effective treatment plan can begin.