Irritable Bowel Syndrome (cont.)
What are the complications of IBS?
The complications of functional diseases of the gastrointestinal tract are
relatively limited. Since symptoms are most often provoked by eating, patients
who alter their diets and reduce their intake of calories may lose weight.
Fortunately, loss of weight is unusual in functional diseases, and it should
suggest the presence of a non-functional disease. Symptoms that awaken patients
from sleep also are more
likely to be due to non-functional than functional diseases.
Most commonly, functional diseases interfere with the patients' comfort and
their daily activities. For example, patients who suffer from morning diarrhea
may not leave their home until the diarrhea stops. If the diarrhea is constant,
they may go only to places where they know that a toilet is readily available.
Patients who develop pain after eating may skip lunch. Very commonly, patients
associate symptoms with specific foods, such as milk, fat, vegetables, etc.
Whether or not these associations are real, these patients will restrict their
diets accordingly. Milk is the food that is most commonly eliminated, often
unnecessarily and to the detriment of adequate calcium intake. The interference
with daily activities also can lead to problems with interpersonal
relationships, especially with spouses. However, most patients with functional
disease tend to just live with their symptoms and infrequently visit physicians
for diagnosis and treatment.
How is IBS diagnosed?
The Rome Criteria
The symptoms of IBS are varied and inconsistent among patients. Moreover,
there are no characteristically abnormal tests that can be used to diagnose IBS.
All of this has made it difficult to define IBS and identify patients,
especially for research studies. In 1999, a group of international investigators
met in Rome for a second time (Rome II). There, they developed a set of criteria
for symptoms to be used for diagnosing IBS.
The Rome II Criteria state that in order to be diagnosed with IBS, a patient
should have suffered abdominal
pain or discomfort for 12 weeks or more (not necessarily consecutive weeks)
in the previous 12 months. The pain or discomfort should have two out of the
three following features:
- Relief with defecation
- Onset associated with a change in the frequency of
stool
- Onset associated with a change in the form of stool
Other symptoms that are not essential, but support a diagnosis of IBS, are:
(1) abnormal frequency of stools (more than 3/day or less than 3/week); (2)
abnormal stool form (lumpy and hard, or loose and watery); (3) abnormal stool
passage (straining, urgency, or feeling of incomplete evacuation); (4) passage
of mucus; and (5) bloating (feeling of abdominal distention, or enlargement).
The Rome II criteria are rather specific for a diagnosis of IBS. In essence,
they require the presence of prolonged abdominal pain or discomfort that is in
some way related to an alteration in the pattern of bowel movements. Symptoms of
dyspepsia (nausea or abdominal discomfort following meals), abdominal
distention, and increased flatus (passing gas, or flatulence) alone do not fall
within this definition. Nevertheless, many patients have these symptoms along
with the symptoms of IBS. It is not clear if these patients have one problem
(IBS) or more than one problem.
In 2006, the group of international investigators met for the third time in Rome and developed the Rome III criteria. A system of classification of gastrointestinal functional disorders came out of this meeting that was much more comprehensive and detailed than prior classifications. The definition of the subcategory, IBS, remained essentially unchanged, however, except for a requirement that the abdominal pain occur at a frequency of at least three times per month. The classification also clearly set apart from IBS three other functional bowel disorders - functional bloating, functional constipation, functional diarrhea, and unspecified functional bowel disorder.
Exclusion of non-functional gastrointestinal disease
As mentioned previously, the exclusion of non-functional disease in patients
with suspected IBS is an important concern. There are many tests to exclude
non-functional diseases. The primary issue, however, is to decide which tests
are reasonable to perform. Since each case is individual, different tests may be
reasonable for different patients. Nevertheless, there are some basic tests that
are often performed to exclude non-functional gastrointestinal disease. These
tests identify anatomic (structural) and histological (microscopic) diseases of
the intestines. As always, a detailed history from the patient and a physical
examination frequently will suggest the cause of symptoms. Routine screening
blood tests often are performed looking for clues to unsuspected diseases.
Examinations of stool also are a part of the evaluation since they may reveal
infection, signs of inflammation, or blood and direct further diagnostic
testing. Sensitive stool testing (antigen/antibody) for Giardia lamblia would be
reasonable because this parasitic infection is common and can be acute or
chronic. Some physicians do blood testing for celiac disease (sprue), but the
value of doing this is unclear. Moreover, if an EGD is planned, biopsies of the
duodenum usually will make the diagnosis of celiac disease. Both X-rays and
endoscopies can identify anatomic diseases. Only endoscopies, however, can
diagnose histological diseases because biopsies (taking samples of tissue) can
be taken during the procedure. The X-ray tests include:
- The esophagram and video-fluoroscopic swallowing
study for examining the esophagus
- The upper gastrointestinal series for examining the
stomach and duodenum
- The small bowel series for examining the small
intestine
- The barium enema for
examining the colon and terminal ileum.
The endoscopic tests include:
- Upper gastrointestinal
endoscopy (esophago-gastro-duodenoscopy, or EGD) to examine the esophagus,
stomach, and duodenum
- Colonoscopy to examine
the colon and terminal ileum
- Endoscopy also is available to examine the small intestine, but this
type of endoscopy is complex, not widely available, and of unproven value in
suspected IBS.
For examination of the small intestine, there is also a capsule containing a
tiny camera that can be swallowed. As the capsule travels through the
intestines, it sends pictures of the inside of the intestines to an external
recorder for later review. However, the capsule is not widely available and its
value in IBS has not yet been proven.
X-rays are easier to perform and are less costly than endoscopies. The skills
necessary to perform X-rays, however, are becoming rarer among radiologists
because they are doing them less often. Therefore, the quality of the X-rays
often is not as high as it used to be. As noted above, endoscopies have an
advantage over X-rays because at the time of endoscopies, biopsies can be taken
to diagnose or exclude histological diseases, something that X-rays cannot do.
Exclusion of non-intestinal disease
Patients with suspected IBS often undergo abdominal ultrasonography (US),
computerized tomography (CT or CAT scans), or
magnetic resonance imaging
(MRI). These tests are used primarily to diagnose non-intestinal diseases.
(Although these tests also may diagnose intestinal diseases, their value for
this purpose is limited. As described above, X-ray and endoscopy are better
tests.) It also is important to realize that US, CT, and MRI are powerful tests
and will uncover abnormalities that are unrelated to IBS. The most common
example is the finding of
gallstones that, in fact, often cause no symptoms. This finding can cause a
problem if the gallstones are assumed to be the source of the IBS symptoms. The
problem is that surgical removal of the gallbladder with its gallstones
(cholecystectomy) is unlikely
to relieve the symptoms of IBS. (Cholecystectomy would be expected to relieve
only the characteristic symptoms that gallstones sometimes can cause.) Tests to
exclude non-intestinal diseases may be appropriate in specific situations,
although certainly not in most patients.
Evaluation of intestinal transportation
If abnormal function of the muscles of the small intestine is suspected,
tests to evaluate transportation through the small intestine or the colon (small
intestinal and colonic transit studies, respectively) are available. These
studies are done with either radioactive compounds or markers that can be seen
on X-rays of the abdomen. It also is possible to pass catheters into the stomach
and small intestine or the colon to determine if the muscles of these organs are
working normally (antro-duodenal and colonic motility studies, respectively).
Finally, constipation due to malfunction of the anal muscles can be diagnosed by
ano-rectal motility studies.
Psychiatric illness
The possibility of psychiatric (psychosomatic) illness often arises in
patients with IBS because the symptoms frequently are subjective, and no
objective abnormalities can be identified. Psychiatric illness may complicate
IBS, but it is unclear if psychiatric illness causes IBS. If there is a
possibility of psychiatric illness, a psychiatric evaluation is appropriate.
Next: How is IBS treated? »
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