“I’m constipated” – What does that mean?
Not
all people mean the same thing when they use the term
“constipation.” In general, “constipation” refers to infrequent or
difficult bowel movements. An individual person’s specific symptoms
may differ from another’s, and may include achieving a bowel movement only
every several days, experiencing difficulty passing stool, having to strain
excessively during a bowel movement, not feeling like a bowel movement has been
complete, passing hard stool, spending too much time trying to have a bowel
movement, needing to use one’s hands to help stool come out, and trying but
failing to have a bowel movement.1-3
It
is important for patients and doctors to communicate clearly about what
patients mean by “constipation.” There may be a tendency to focus on
how often a person achieves bowel movements, with at least 3 bowel movements
per week being considered “normal.” But many times patients are bothered
by the multiple symptoms of difficult stool passage, even if they achieve
several bowel movements per week or even every day.
Formal definitions of constipation
The
American College of Gastroenterology Chronic Constipation Task Force recommended
a broad definition of constipation that captures the symptoms of patients who
report that they are constipated:1, 4
“Constipation is a symptom-based disorder defined as unsatisfactory defecation [“defecation” is the passing of stool] and is characterized by infrequent stools, difficult stool passage, or both. Difficult stool passage includes straining, a sense of difficulty passing stool, incomplete evacuation, hard/lumpy stools, prolonged time to stool, or need for manual maneuvers to pass stool. Chronic constipation is defined as the presence of these symptoms for at least 3 months.”
Most
of the time, there is no specific explanation for constipation, and it is
considered “functional,” meaning that symptoms are present without a clear
underlying abnormality. Leading researchers have met periodically in
Rome since the 1980s, and have proposed symptom-based criteria for the
functional gastrointestinal disorders. The Rome III definition of
functional constipation, proposed in 2006, is “a functional bowel disorder that
presents as persistently difficult, infrequent, or seemingly incomplete
defecation, which does not meet Irritable Bowel Syndrome criteria.”3 Irritable
bowel syndrome, or IBS, is a syndrome characterized by abdominal pain or
discomfort and altered bowel movements, which can include constipation,
diarrhea, or both. Some propose that chronic constipation and IBS
lie along a spectrum, with pain or discomfort being very prominent in IBS, but
milder and rarer in chronic constipation. The Rome III diagnostic
criteria for functional constipation, which are meant to be used in clinical
research but are not practical for clinical care, are the following:3
1. Must
include two or more of the following:
a. Straining
during at least 25% of defecations
b. Lumpy
or hard stools in at least 25% of defecations
c. Sensation
of incomplete evacuation for at least 25% of defecations
d. Sensation
of anorectal obstruction/blockage for at least 25% of defecations
e. Manual
maneuvers to facilitate at least 25% of defecations (e.g. removal
of stool with the fingers, or applying support around the anus with the hand)
f. Fewer
than 3 defecations per week
2. Loose
stools are rarely present without the use of laxatives
3. There
are insufficient criteria for Irritable Bowel Syndrome (IBS)
* Criteria
fulfilled for the last 3 months with symptom onset at least 6 months prior to
diagnosis
These
formal definitions highlight the fact that infrequent bowel movements may be
part of the group of symptoms that patients with “constipation” experience, but
are not necessarily the principal feature.
“I only have two bowel
movements a week. Should I worry?”
A
common misconception is that a daily bowel movement is necessary for good
health, and that failure to empty stool promptly can lead to “toxic”
consequences for the body.5 The modern concern with the
need to have a daily bowel movement has its root in the old idea of “autointoxication,”
which is the belief that toxins can form when undigested food stays in the
large intestine (the colon) for too long, and can then be absorbed into the
body and cause all kinds of symptoms and health problems.5 There
is no scientific evidence to support these ideas.
It is important to dispel fear in persons who do not achieve a daily
bowel movement in order to avoid unnecessary interventions such as purges,
enemas, and “cleansing” regimens. Some persons see a doctor out of
concern that they have bowel movements only a few times a week, but they
actually feel fine. For these patients, it is important to provide
reassurance that they do not have a “medical problem.” As discussed
below, it is recommended that constipation be treated only when it impairs a
person’s quality of life.1
What causes constipation? Are there subtypes of constipation?
Constipation
can be considered “primary” when no clear cause is evident, and “secondary”
when there is an underlying factor or illness that can explain the
constipation. Common causes of “secondary” constipation include
medications (classic examples are the potent pain medications of the narcotic
class, including the opioids codeine and morphine, but many other medications
can also cause constipation), metabolic diseases such as diabetes, neurologic
diseases such as Parkinson’s disease, and pregnancy. It is
recommended that opioid medications be prescribed with a bowel regimen
including stool softeners or laxatives in order to prevent constipation.
What
causes “primary” constipation? When patients with constipation are
studied with specialized physiologic tests, some patients demonstrate specific
findings.6, 7 A subgroup of patients has very slow
passage, or transit, of stool through the colon (slow-transit
constipation). In some of these patients, the nerves of the colon
may be abnormal. Another subgroup has difficulty actually pushing
out the stool from the rectum (defecatory disorders, which are referred to by
numerous names including obstructed defecation, pelvic floor dysfunction,
pelvic floor dyssynergia, anismus, and spastic pelvic floor). In
these patients, there may be abnormalities in the muscle and nerve function of
the rectum, anus, and the complex set of muscles in the floor of the pelvis,
all of which must act in coordination to expel stool. A small
minority has both slow transit and a defecatory disorder.
A
significant fraction of persons with constipation has normal passage time
through the colon and no obvious abnormality in the nerve and muscle function
needed to expel stool from the rectum (normal-transit
constipation). In these patients, constipation is probably explained
by the perceived difficulty in achieving a bowel movement or by the presence of
hard stools.2
Normal function of the colon, rectum and anus, and abnormalities in constipation
Understanding
the normal function of the colon, rectum, and anus6 allows
appreciation of the differences between the subgroups of primary constipation.
The
right side of the colon serves to store and mix stool contents, the left side
of the colon serves for storage and as a conduit of stool to the rectum, and
along the length of the colon there is absorption of salts and water. Thus,
the stool content in the right colon is generally looser than in the left
colon. There are several patterns of normal muscle activity in the
colon, including contractions that travel for long distances along the colon, contractions
that don’t seem to travel much, and slow and steady
contractions. Powerful contractions that form a traveling wave down
the colon can move stool contents for significant distances. These
often occur early in the morning, and are related to the morning bowel movement
that is typical for many persons. They can also occur after meals,
and explain why some people feel the need to have a bowel movement after
eating. During these after-meal bowel movements, it is not the meal
that was just eaten that is eliminated, but rather stool that has been produced
after previous meals. Persons with slow-transit constipation may
demonstrate abnormalities in the motor activity of the colon, but the range of
“normal” is broad, and there is no single pattern that is classic for slow-transit
constipation.
The
rectum is the reservoir at the end of the colon, where stool is present before
it is eliminated. The anal sphincter is the ring of muscle just
beyond the rectum that prevents stool from leaking out. Most of the
time, pelvic muscles (the puborectalis sling) pull forward on the rectum,
keeping it an angle, and the anal sphincter is contracted. Both of
these conditions prevent the passage of stool. The normal process of
having a bowel movement involves relaxation of the puborectalis sling, thus
allowing the rectum to straighten, and relaxation of the anal
sphincter. “Bearing down” increases the pressure inside the abdomen,
and this can help the passage of stool when the rectum is straight and the anal
sphincter is relaxed. Patients with disorders of defecation may
exhibit lack of coordination of these functions. For instance, they
may bear down while also contracting (instead of relaxing) the puborectalis
sling and the anal sphincter. This amounts to “pushing against a
closed outlet.”
How common is
constipation?
It
is estimated that in North America, 12% to 19% of people have constipation, and
that over 60 million people meet Rome criteria for the diagnosis of
constipation.8 Taking all available studies, the
estimates reported for the fraction of the population with constipation ranges
from 2% to 27%. These studies have used different definitions of
constipation and different ways of estimating how common constipation is, which
likely explains the wide range in the estimates. Most patients who
report constipation still have the condition one year later.
Research
studies have identified subpopulations that are more likely to experience
constipation.8 Women are twice as likely as men to have constipation. Non-white
persons seem to have a higher rate of constipation. The elderly are
more likely than younger persons to suffer from
constipation. Constipation is more commonly reported by persons with
lower socioeconomic status.
What routine medical
tests should be done in patients with constipation?
There
are few research studies that address the usefulness of specific tests in the
evaluation of patients with constipation.9 The current
consensus is that there is no evidence to support the routine use of blood
tests, x-ray studies, or endoscopy (sigmoidoscopy or colonoscopy) in persons
with constipation.1, 9
In
persons who are age 50 years and older, it is reasonable to offer screening for
colorectal cancer, as is recommended for all persons, even those without
symptoms.1 The available evidence suggests that persons
with chronic constipation who undergo sigmoidoscopy or colonoscopy (exams of
the end portion of the colon or the entire colon with a flexible tube with a
camera at the tip) are likely to have colon cancer and polyps (growths that
could turn into cancer) at the same rate as persons without symptoms.10
Specialized
tests may be useful in persons who have constipation that is difficult to
treat. This is particularly the case when it comes to identifying
those persons with extremely slow colonic transit, or defecation disorders,
because different specific therapies may be offered to these subgroups of
patients.
How should the constipated patient be approached in primary care practice?
Current
expert opinion holds that in younger patients with chronic constipation and no
“alarm signs” or clinical features to suggest a specific underlying disease, no
medical testing is necessary.1, 3, 4 “Alarm signs” may
indicate more serious underlying disease, and it is recommended that testing be
performed in patients with these signs, which include bleeding from the rectum,
weight loss of 10 pounds or more, family history of colon cancer or
inflammatory bowel disease (ulcerative colitis or Crohn’s disease), anemia (low
blood count), positive fecal occult blood test (hidden blood in the stool), as
well as the acute onset of symptoms in elderly persons.1, 4 Physicians
should determine whether individual patients should have blood tests (e.g., to
establish if high calcium or low thyroid hormone levels could be causing
constipation), or other tests including sigmoidoscopy or
colonoscopy. Persons who are candidates for colon cancer screening,
including those who are age 50 years and older, should be offered screening.1
Treatment
of constipation should be based on the severity of symptoms and their impact on
a patient’s quality of life.1 First, it must be
determined whether the patient is bothered by the “constipation” or only by theidea of
“being constipated.” Patients may be reassured that achieving a
bowel movement every several days is in the range of normal, and that having
infrequent bowel movements is not harmful in and of itself. Those
with troubling bowel symptoms should be offered treatment for their
constipation.
It
is a popular belief that people with constipation do not have enough fiber in
their diet, do not drink enough water, and do not exercise enough.5 Although
there is not much research in the area, it seems that fiber intake may not be
very different in those with constipation compared to those
without. However, some persons with constipation can improve with
fiber supplements, as discussed below. Drinking more water would not
be expected to affect the hardness of stool, because the small intestine has a
very high capacity to absorb water, and in fact there is no evidence that
drinking more fluid can treat constipation. Some patients report
that exercise regularizes their bowel movements, although there are no good
studies that support this as a treatment for
constipation. Regardless, it is good general advice for people to
engage in regular
exercise.
For
many persons with regular bowel movements, part of their “regularity” seems to
be a behavior pattern that takes advantage of the times when the colon is
normally active, such as in the morning and after meals. Patients
with constipation should be advised to listen to their body and go to the bathroom
when they feel the urge to have a bowel movement, particularly upon awakening
and after eating. They should not spend excessive time in the
bathroom straining, however.
What medical
treatments are available for constipation?
The
available medical therapies for constipation include bulking agents, stool
softeners, laxatives, enemas, and prescription drugs. Many of the
traditional treatments, including fiber supplements and some laxatives and
stimulants, have not been studied in rigorous clinical trials.11 Although
there is insufficient evidence to make formal recommendations for these
treatments in practice guidelines,1 some patients do benefit
from these traditional therapies, and it is reasonable to try these before
prescription medications are considered.
Stool
bulking agents can bind water and thus may increase the solid as well as the
water content of stool. The bulking agents include psyllium products
(e.g. Metamucil, Konsyl, Perdiem, and multiple supplements), calcium
polycarbophil (e.g. Fibercon), methylcellulose (e.g. Citrucel),
wheat dextrin (e.g.Benefiber), and bran. Available evidence
suggests that psyllium increases stool frequency, but there is insufficient
evidence to make firm recommendations about other bulking agents.1 In
clinical practice and in the over-the-counter setting, bulking agents can help
some persons with constipation. Bulking agents make some patients
feel worse. Bloating, for instance, may worsen. In these
persons, the agents should be stopped. There is no reason to increase the
dose of these treatments to high levels in those who do not benefit from
standard doses.5
There
is limited evidence on stool softeners such as docusate sodium (e.g., Colace)
or docusate calcium (e.g., Surfak) and some of the results of
clinical trials are conflicting. These agents are like detergents
that allow water to mix better with stool. Stool softeners may have
some, possibly minimal, benefit in constipation.1
There
are two major types of laxatives. Osmotic laxatives are substances
that tend to stay inside the intestines instead of being absorbed into the
body. When these substances stay in the intestines, they retain
fluid, and they can promote the transit of stool as well as make the stool
softer or even loose. Stimulant laxatives are believed to activate
nerves that control the muscle function of the colon as well as affect
absorption of salts and water, thereby promoting stool transit and lessening
the hardness of stool. Overuse of laxatives can lead to diarrhea and
significant imbalances in the levels of salts in the blood, so caution must be
exercised when using these therapies.
Polyethylene
glycol (e.g., MiraLax, GlycoLax) is a well-studied osmotic
laxative. Until recently, this medication was available in the
United States only by prescription, but it is now available over the
counter. Several studies have assessed the benefit of polyethylene glycol
in constipation.1 Polyethylene glycol has been shown to
increase stool frequency and improve stool consistency. Some
patients experience bloating, cramping, and nausea with this medication.
Lactulose
(e.g., Kristalose, Chronulac), another osmotic laxative, is a sugar
that cannot be processed by humans, and passes undigested into the
colon. Lactulose also improves stool frequency and consistency.1 Colonic
bacteria are able to digest lactulose, and this can produce gas and
bloating. Sorbitol is a similar agent that is poorly absorbed and
can be fermented by bacteria in the colon.
Other
osmotic laxatives include magnesium citrate and magnesium hydroxide (milk of
magnesia).2 These agents have not been well studied, but in
clinical practice, they can be useful in treating constipation. In
people with kidney problems, abnormal levels of salts in the blood can develop
with these agents.
The
stimulant laxatives have not been well studied in clinical trials, but they are
commonly used. Many agents are available over the
counter. Common beliefs are that these agents can harm the colon in
the long term, can make the colon “lazy,” or can be
“addicting.” However, there is no evidence to support these notions.5 Many
of the stimulant laxatives contain senna (e.g., Ex-Lax,
Senokot). Bisacodyl is also common (e.g., Dulcolax,
Correctol). Some contain cascara sagrada. These agents
may work best if they are used two or three times a week instead of daily, in
combination with daily non-stimulant laxatives.5 Some
patients can be treated successfully with these agents for many
years. For these patients, there does not seem to be a compelling
reason to stop these agents or switch to another treatment.
Other
traditional treatments do not fit into the categories described
above. They include mineral oil, suppositories, and
enemas. Herbal therapies and teas have not been well studied, and it
is often not possible to know what is in these
preparations. However, some patients rely on these remedies to
manage their constipation.
In
recent years, two new prescription drugs became available for the treatment of
chronic constipation. Tegaserod (Zelnorm) was first approved for women
with constipation-predominant IBS, and later for women and men with chronic
constipation.1, 4 Tegaserod increases the number of complete,
spontaneous bowel movements per week. The marketing of tegaserod was
suspended recently because review of clinical data revealed more adverse
cardiovascular events in patients treated with tegaserod than in those treated
with a placebo (an inactive substance) in clinical studies. Until recent,
selected patientsly, selected patients could be eligible to participate in a
restricted treatment program (“treatment IND”) for women under the age of 55
years with constipation-predominant IBS or chronic idiopathic constipation
(“idiopathic” means of unknown origin), who did not have satisfactory response
to other available treatments, and/or patients who had satisfactory improvement
of their symptoms with prior tegaserod treatment. Patients were
excluded for a history, current diagnosis, or symptoms of cardiovascular
ischemic disease, the presence of any cardiovascular risk factors according to
National Institutes of Health guidelines, or uncompensated depression, anxiety,
or suicidal ideation or behavior. The IND program is not currently
available.
The
most recently approved medication for constipation in the United States is
lubiprostone (Amitiza).12 Lubiprostone increases the number of
spontaneous bowel movements per week. Nausea can be a side effect of
this medication, but it seems to be less common when the medication is taken
with food.
There
are medications for other conditions that are recognized to have diarrhea as a
side effect. These include colchicine and
misoprostol. These medications are sometimes used to treat patients
with constipation.
What specialized tests
should be considered in patients with constipation that is difficult to
treat? How do these affect how patients are managed?
Patients
who do not respond to medical treatments for constipation should be referred
for specialty evaluation.13, 14 Testing to determine
which patients have slow colonic transit6, 7 and which patients
have defecation disorders6, 7 is likely to alter their
management.
Colonic
transit is commonly measured by asking the patient to swallow a capsule that
contains 24 small rings, or markers, that can be seen on x-ray. An
x-ray taken one day later should show the markers in the colon. If
they are in the stomach or small intestine, then transit time through the
stomach or small bowel is severely abnormal. If an x-ray taken five
days after the capsule is swallowed shows 4 or fewer markers still left in the
colon, this indicates that the person has normal colonic
transit. The rest of the markers will have been passed before the
fifth day. If 5 or more markers remain in the colon and they are
scattered throughout the right and left side, this is consistent with slow-transit
constipation. If multiple markers are retained at day five, but
appear to be bunched in the lower left colon (the sigmoid colon) and rectum,
this could indicate a defecation disorder. Other methods to test
colonic transit are available, including methods that use a small amount of
radioactivity (scintigraphy).
Several
tests can be used to assess whether defecation is
abnormal. Anorectal manometry is the measurement of the pressures in
the anus and rectum at rest and with squeezing. Persons with
abnormal defecation may have pressures in the rectum during attempted
defecation that are too low to overcome the resistance at the anus.6, 7 The
normal physiologic pattern is for the rectal pressure to increase and the anal
pressure to decrease during attempted defecation. The classic
pattern in disordered defecation, or pelvic floor dysfunction, is for the
pressure in the anus to also increase.7 Patients may also
have abnormal sensation in the rectum, becoming aware of an inflated balloon
only at larger than normal levels.
In
the balloon expulsion test, patients are asked to push out a balloon that is
placed in the rectum, to simulate the process of passing stool. Most
persons with normal defecation succeed in 1 minute or less. If
patients are not successful after 3 minutes, they are likely to have a disorder
of defecation.7
Disordered
defecation is managed with biofeedback in addition to medical treatments.7 Several
sessions are provided in order to help patients retrain themselves to contract
and relax the appropriate muscles in order to achieve more satisfactory passage
of stool.
A
radiologic test called defecography consists of asking the patient to pass a
pasty barium material that simulates soft stool while x-ray pictures are
taken. This allows measurement of whether the rectum is
straightening properly or whether there is an abnormal bulge in the rectum
(rectocele) that may be associated with failure to pass the
paste. Rectoceles are relatively common, and most of the time they
do not need to be treated surgically.
Hirschsprung’s
disease is an extreme form of abnormal nerve content of the rectum and colon,
which can involve only a small stretch of the intestine or a large
segment. Normally, inflating a balloon in the rectum produces a
reflex that relaxes the internal anal sphincter (the rectoanal inhibitory
reflex). “Potty training” includes learning to squeeze the external
anal sphincter when stool in the rectum causes the internal anal sphincter to
relax, in order to prevent stool from passing when it is not socially
appropriate. If the rectoanal inhibitory reflex is not present
during anorectal manometry, a sample of the tissue from the rectum is obtained
in order to evaluate for the possibility of Hirschsprung’s disease, which is
treated by surgically removing the affected segment of non-functioning
intestine. This condition is generally, but not always, diagnosed
during childhood.
Is there a role for
surgery in patients with constipation?
The
extreme form of slow-transit constipation is called colonic
inertia. In patients with extremely slow colonic transit, removing
the colon may be necessary in order to manage their
constipation. Patients who also have extremely slow transit through the
small intestine will not fare as well after colonic resection, and this group
must be approached with caution. Patients should be educated about
the fact that removing the colon is expected to help with the frequency of
bowel movements and the symptoms associated with stool retention. However,
if patients also have chronic abdominal pain, the pain may not
improve. Persons with slow-transit constipation as well as
disordered defecation must have treatment of the disordered defecation with
biofeedback before an operation is considered. The currently
recommended operation for colonic inertia is removal of the entire colon, with
attachment of the end portion of the small intestine to the rectum (colectomy
with ileorectal anastomosis).14, 15
Conclusion
Constipation
is characterized by infrequent and/or difficult passage of stool. It
is a very common condition. Most of the time, it is not associated
with an underlying disease. It is not necessary to achieve a daily
bowel movement in order to be healthy. Therefore, constipation
should be treated only if symptoms are bothersome and affect a person’s quality
of life. Routine medical testing is not necessary in persons with
chronic constipation, but age-appropriate colorectal cancer screening should be
offered. Multiple non-prescription treatments and several
prescription medications are available. Many of the traditional
treatments for constipation have not been studied rigorously in clinical
trials, but they can be effective and they remain important alternatives in the
treatment of patients. In persons who do not respond to treatment,
specialized testing should be performed in order to identify persons with
disorders of defecation, which can be treated with biofeedback, and slow
colonic transit. The extreme form of slow colonic transit, colonic
inertia, can be treated by removing the colon surgically.
