In most cases, the cause of constipation can be determined by a careful
case history and physical examination. Alarm signs such as blood in stools,
recent changes in bowel movements, or weight loss merit particularly close
Bowel transit studies using a marker such as activated charcoal are simple
and effective; while referral for more sophisticated X-ray studies using
radio-opaque markers may reveal more detailed information.
Digital rectal exam can be used to assess anal sphincter tone,
while referral for more sophisticated anorectal manometry can be used to
evaluate anal sphincter muscle function,
and can be used to evaluate a recommendation for biofeedback training.
Sigmoidoscopy can be used to examine the rectum and lower colon (sigmoid colon).
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 necessary.
Depending on the age of the patient and the level of suspicion,
a referral for a complete colonoscopy may be indicated.
Referral for barium enema X-ray study may be indicated in cases with alarm signs.
Referral for defecography (an X-ray study of the defecation process) may
be needed to assess anorectal dysfunction.