A 29-year-old woman presents with a 6-month history of recurrent abdominal
pain associated with bloating and altered bowel habits. She reports episodes of
diarrhea alternating with constipation. Her symptoms are often worse during
periods of stress and improve after defecation. She denies fever, weight loss,
rectal bleeding, or nocturnal symptoms. Physical examination is unremarkable.
Laboratory investigations including CBC, CRP, celiac serology, and stool
studies are normal. Diagnosis?
Most likely diagnosis is Irritable Bowel Syndrome with mixed bowel
habits (IBS-M).
The clinical presentation is highly characteristic of IBS-M.
Strict fulfillment of Rome V criteria additionally requires
recurrent, noncontinuous abdominal pain or discomfort occurring on average at
least 3 days per month during the last 3 months, with symptom
onset at least 6 months before diagnosis.
1. Definition
1. Irritable
bowel syndrome is a chronic disorder of gut-brain interaction (DGBI).
2. It
is characterized by:
1.
Recurrent abdominal pain or discomfort
2.
Altered bowel habits
3.
Symptoms not adequately explained by another medical
condition after appropriate clinical evaluation
3. IBS
is a positive clinical diagnosis based on characteristic
symptoms, appropriate limited investigation, and assessment for alarm features.
2. Etiology / Associations
1. The
pathogenesis is multifactorial and incompletely understood.
2. Factors
that may contribute include:
1.
Altered gastrointestinal motility
2.
Visceral hypersensitivity
3.
Altered gut-brain signaling
4.
Psychological and physiologic stress
5.
Alterations in the intestinal microbiota
6.
Post-infectious changes
7.
Mucosal immune activation
8.
Altered intestinal permeability in some patients
3. Associated
conditions include:
1.
Anxiety disorders
2.
Depression
3.
Fibromyalgia
4.
Chronic fatigue syndromes
5.
Other disorders of gut-brain interaction
3. Pathophysiology
1. Visceral
hypersensitivity contributes to exaggerated perception of intestinal
stimuli.
2. Altered
gastrointestinal motility may contribute to constipation, diarrhea, or mixed
bowel patterns.
3. Altered
central and enteric nervous system processing contributes to abnormal gut-brain
signaling.
4. Stress
may influence gastrointestinal motility, sensation, and symptom severity.
5. Alterations
in the intestinal microbiota, mucosal immune activation, and increased
intestinal permeability may contribute in subsets of patients.
6. No
single pathophysiologic abnormality explains IBS in all patients.
4. Clinical Features
4.1 Abdominal Symptoms
1. Recurrent
abdominal pain or discomfort
2. Symptoms
related to defecation
1.
Symptoms may improve or occasionally worsen with
defecation
3. Bloating
4. Abdominal
distension
5. Excessive
flatulence
4.2 Bowel Habit Changes
1. Constipation
2. Diarrhea
3. Mixed
constipation and diarrhea
4. Passage
of mucus
5. Sensation
of incomplete evacuation
6. Urgency
4.3 Associated Features
1. Fatigue
2. Sleep
disturbance
3. Anxiety
or depression
4. Urinary
symptoms
5. Other
functional gastrointestinal symptoms may coexist
4.4 Alarm Features / Red Flags
1. Unintentional
weight loss
2. Gastrointestinal
bleeding
3. Iron
deficiency anemia
4. Persistent
nocturnal diarrhea
5. Fever
6. Palpable
abdominal or rectal mass
7. Family
history of colorectal cancer, inflammatory bowel disease, or celiac disease
8. New
onset of symptoms at age 50 years or older
9. Need
for age-appropriate colorectal cancer screening
10. Progressive,
severe, or otherwise atypical symptoms
5. Diagnosis
5.1 Rome V Criteria
Recurrent, but not continuous, abdominal pain or discomfort
occurring on average at least 3 days per month during the last 3 months,
associated with at least two of the following:
1. Related
to defecation
2. Associated
with a change in stool frequency
3. Associated
with a change in stool form or appearance
Criteria should be fulfilled during the last 3 months, with symptom onset at
least 6 months before diagnosis.
A supportive criterion is that abdominal pain or discomfort should not occur
exclusively in relation to menstruation.
5.2 IBS Subtypes
IBS subtypes are classified using the Bristol Stool Form Scale
according to stool form on days with abnormal bowel movements.
1. IBS-C:
Constipation predominant
1.
More than 25% of abnormal bowel
movements are Bristol Stool Form Scale types 1 or 2
2.
Fewer than 25% of abnormal bowel
movements are types 6 or 7
2. IBS-D:
Diarrhea predominant
1.
More than 25% of abnormal bowel
movements are types 6 or 7
2.
Fewer than 25% of abnormal bowel
movements are types 1 or 2
3. IBS-M:
Mixed bowel habits
1.
More than 25% of abnormal bowel
movements are types 1 or 2
2.
More than 25% of abnormal bowel
movements are types 6 or 7
4. IBS-U:
Unclassified
1.
Diagnostic criteria for IBS are met, but the bowel
pattern does not fulfill criteria for IBS-C, IBS-D, or IBS-M
Subtype assessment is preferably performed when the patient is not taking medications
that substantially alter bowel habits.
5.3 Investigations
1. Investigation
should be limited and guided by the clinical presentation.
2. Appropriate
tests may include:
1.
CBC
2.
CRP
3.
Celiac serology, particularly in
patients with diarrhea symptoms
4.
Fecal calprotectin in patients with
diarrhea symptoms when inflammatory bowel disease needs to be excluded
3. Routine
stool testing for enteric pathogens is not recommended in all patients with
suspected IBS.
4. Stool
infectious testing should be performed when clinically indicated, such as with
relevant travel, exposure, epidemiologic risk, or suspected infection.
5. Routine
colonoscopy is not required in a young patient with typical IBS
symptoms and no alarm features.
6. Colonoscopy
should be considered when:
1.
Alarm features are present
2.
Age-appropriate colorectal cancer screening is
indicated
3.
Significant diagnostic uncertainty remains
4.
Microscopic colitis or another colonic disorder is
suspected
6. Differential Diagnosis
1. Inflammatory
bowel disease
2. Celiac
disease
3. Microscopic
colitis
4. Bile
acid diarrhea
5. Lactose
or other carbohydrate intolerance
6. Chronic
gastrointestinal infection when epidemiologically appropriate
7. Colorectal
neoplasia
8. Thyroid
disease when clinically suspected
9. Medication-induced
bowel disturbance
10. Small
intestinal bacterial overgrowth in selected patients with appropriate risk
factors
11. Pelvic
floor dysfunction in patients with refractory constipation or symptoms of
difficult evacuation
12. Gynecologic
disorders such as endometriosis when symptoms are pelvic or cyclical
7. Management
Treatment should be individualized according to the predominant symptoms and
IBS subtype.
7.1 General Measures
1. Establish
a clear positive diagnosis.
2. Provide
education regarding the chronic nature of the disorder.
3. Identify
individual symptom triggers.
4. Encourage
regular physical activity.
5. Encourage
adequate sleep.
6. Address
stress and relevant psychological comorbidities.
7. Establish
a therapeutic clinician-patient relationship and provide realistic treatment
expectations.
7.2 Dietary Therapy
1. Soluble
fiber such as psyllium may improve global IBS symptoms.
2. Insoluble
fiber such as wheat bran may worsen symptoms in some patients.
3. A
limited trial of a low-FODMAP diet may improve global IBS
symptoms.
4. Low-FODMAP
therapy generally involves:
1.
Short-term restriction, usually approximately 4
to 6 weeks
2.
Systematic food reintroduction
3.
Long-term dietary personalization
5. Dietitian
supervision is preferable when a restrictive diet is used.
6. Dietary
triggers should be individualized. Routine universal avoidance of caffeine,
alcohol, high-fat foods, or lactose is unnecessary unless they provoke symptoms
in the individual patient.
7.3 Pharmacologic Therapy
IBS-C
1. Soluble
fiber such as psyllium
2. Polyethylene
glycol for constipation
1.
Improves stool frequency and consistency
2.
Is less reliable for improving abdominal pain or global
IBS symptoms
3. Linaclotide
4. Plecanatide
5. Lubiprostone
6. Tenapanor
IBS-D
1. Loperamide
1.
Useful for reducing diarrhea and urgency
2.
Less effective for abdominal pain or global IBS
symptoms
2. Rifaximin
3. Eluxadoline
in appropriately selected patients
1.
Contraindicated in patients without a gallbladder
2.
Avoid in patients with a history of pancreatitis,
sphincter of Oddi dysfunction, biliary obstruction, substantial alcohol use, or
severe hepatic impairment
4. Alosetron
may be considered for severe refractory IBS-D in women where approved and
appropriately regulated.
5. Bile
acid sequestrants are not routine treatment for global IBS-D symptoms but may
be useful when bile acid diarrhea is suspected or demonstrated.
Abdominal Pain / Global Symptoms
1. Low-dose
tricyclic antidepressants
1.
May improve abdominal pain and global IBS symptoms
2.
May be particularly useful in IBS-D because they can
slow gastrointestinal transit
3.
Should be used cautiously in IBS-C because
anticholinergic effects may worsen constipation
2. Enteric-coated
peppermint oil may improve abdominal pain and global symptoms.
3. Antispasmodics
may improve episodic abdominal pain in some patients, although recommendations
vary among clinical guidelines.
4. SSRIs
should not be routinely prescribed solely for treatment of global IBS symptoms
but may be appropriate when there is an independent psychiatric indication.
5. Chronic
opioid therapy should be avoided for IBS-related abdominal pain.
7.4 Gut-Brain Behavioral Therapy
1. Cognitive
behavioral therapy
2. Gut-directed
hypnotherapy
3. Other
evidence-based gut-brain behavioral interventions
4. Stress-management
techniques as an adjunct to treatment
Gut-brain behavioral therapies may improve global IBS symptoms and should
not be regarded solely as treatments for psychiatric disease.
8. Monitoring
1. Monitor
symptom burden and quality of life.
2. Assess
response to dietary and pharmacologic therapy.
3. Reevaluate
the diagnosis if new alarm features develop.
4. Reassess
patients whose clinical pattern changes substantially.
5. Avoid
repeated or extensive investigations in a stable patient with a
well-established diagnosis unless a new clinical indication develops.
9. Complications / Prognosis
1. Reduced
quality of life
2. Work
and social impairment
3. Increased
healthcare utilization
4. Anxiety
and depression may coexist and increase symptom burden
5. IBS
does not cause destructive intestinal mucosal disease.
6. IBS
is not considered a premalignant disorder.
7. Current
evidence does not support IBS itself causing an increased long-term risk of
colorectal cancer.
10. Key Clinical Insight
Chronic recurrent abdominal pain or discomfort related to defecation and
associated with altered stool frequency or form, in a patient without alarm
features and with an appropriate limited negative evaluation, strongly supports
a positive diagnosis of IBS.
In this patient, alternating constipation and diarrhea are most consistent
with IBS-M. Formal subtype classification is based on the Bristol
Stool Form Scale and the proportion of abnormal bowel movements.
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