What Diagnostic Tests Are Used?
Most people do not need extensive
testing and can be treated with changes in diet and exercise.
For example, in young people with mild symptoms, a medical
history and physical examination may be all the doctor needs to
suggest successful treatment. The tests the doctor performs
depends on the duration and severity of the constipation, the
person's age, and whether there is blood in stools, recent
changes in bowel movements, or weight loss.
The doctor may ask a patient to describe his or her
constipation, including duration of symptoms, frequency of bowel
movements, consistency of stools, presence of blood in the
stool, and toilet habits (how often and where one has bowel
movements). Recording eating habits, medication, and level of
physical activity or exercise also helps the doctor determine
the cause of constipation.
A physical exam may include a digital rectal exam with a gloved,
lubricated finger to evaluate the tone of the muscle that closes
off the anus (anal sphincter) and to detect tenderness,
obstruction, or blood. In some cases, blood and thyroid tests
may be necessary.
Extensive testing usually is reserved for people with severe
symptoms, for those with sudden changes in number and
consistency of bowel movements or blood in the stool, and for
older adults. Because of an increased risk of colorectal cancer
in older adults, the doctor may use these tests to rule out a
diagnosis of cancer:
Barium Enema X-Ray
A barium enema x-ray involves viewing the rectum, colon, and
lower part of the small intestine to locate any problems. This
part of the digestive tract is known as the bowel. This test
may show intestinal obstruction and Hirschsprung's disease, a
lack of nerves within the colon.
The night before the test, bowel cleansing, also called bowel
prep, is necessary to clear the lower digestive tract. The
patient drinks 8 ounces of a special liquid every 15 minutes for
about 4 hours. This liquid flushes out the bowel. A clean
bowel is important, because even a small amount of stool in the
colon can hide details and result in an inaccurate exam.
Because the colon does not show up well on an x-ray, the doctor
fills the organs with a barium enema, a chalky liquid to make
the area visible. Once the mixture coats the organs, x-rays are
taken that reveal their shape and condition. The patient may
feel some abdominal cramping when the barium fills the colon,
but usually feels little discomfort after the procedure. Stools
may be a whitish color for a few days after the exam.
Sigmoidoscopy or Colonoscopy
An examination of the rectum and lower colon (sigmoid) is called
a sigmoidoscopy. An examination of the rectum and entire colon
is called a colonoscopy.
The night before a sigmoidoscopy, the patient usually has a
liquid dinner and takes an enema in the early morning. A light breakfast
and a cleansing enema an hour before the test may also be
To perform a sigmoidoscopy, the doctor uses a long, flexible
tube with a light on the end called a sigmoidoscope to view the
rectum and lower colon. First, the doctor examines the rectum
with a gloved, lubricated finger. Then, the sigmoidoscope is
inserted through the anus into the rectum and lower colon. The
procedure may cause a mild sensation of wanting to move the
bowels and abdominal pressure. Sometimes the doctor fills the
organs with air to get a better view. The air may cause mild
To perform a colonoscopy, the doctor uses a flexible tube with a
light on the end called a colonoscope to view the entire colon.
This tube is longer than a sigmoidoscope. The same bowel
cleansing used for the barium x-ray is needed to clear the
bowel of waste. The patient is lightly sedated before the exam.
During the exam, the patient lies on his or her side and the
doctor inserts the tube through the anus and rectum into the
colon. If an abnormality is seen, the doctor can use the
colonoscope to remove a small piece of tissue for examination
(biopsy). The patient may feel gassy and bloated after the
Colorectal Transit Study
This test, reserved for those with chronic constipation, shows
how well food moves through the colon. The patient swallows
capsules containing small markers, which are visible on x-ray.
The movement of the markers through the colon is monitored with
abdominal x-rays taken several times 3 to 7 days after the
capsule is swallowed. The patient follows a high-fiber diet
during the course of this test.
Anorectal Function Tests
These tests diagnose constipation caused by abnormal functioning
of the anus or rectum (anorectal function). Anorectal manometry
evaluates anal sphincter muscle function. A catheter or
air-filled balloon inserted into the anus is slowly pulled back
through the sphincter muscle to measure muscle tone and
Defecography is an x-ray of the anorectal area that evaluates
completeness of stool elimination, identifies anorectal
abnormalities, and evaluates rectal muscle contractions and
relaxation. During the exam, the doctor fills the rectum with a
soft paste that is the same consistency as stool. The patient
sits on a toilet positioned inside an x-ray machine and then
relaxes and squeezes the anus and expels the solution. The
doctor studies the x-rays for anorectal problems that occurred
while the patient emptied the paste.
- Barium enema x-ray
- Sigmoidoscopy or colonoscopy
- Colorectal transit study
- Anorectal function tests.