LECTURE

1. Constipation
Constipation is difficult or infrequent passage of stool, hardness of
stool, or a feeling of incomplete evacuation.
Many people incorrectly believe that daily defecation is necessary
and complain of constipation if stools occur less frequently. Others
are concerned with the appearance (size, shape, color) or
consistency of stools. Sometimes the major complaint is
dissatisfaction with the act of defecation or the sense of incomplete
evacuation after defecation. Constipation is blamed for many
complaints (abdominal pain, nausea, fatigue, anorexia) that are
actually symptoms of an underlying problem (eg, irritable bowel
syndrome [IBS], depression). Patients should not expect all
symptoms to be relieved by a daily bowel movement, and measures
to aid bowel habits should be used judiciously.
Obsessive-compulsive patients often feel the need to rid
the body daily of “unclean” wastes. Such patients often
spend excessive time on the toilet or become chronic
users of cathartics.
Etiology
Acute constipation suggests an organic cause, whereas chronic
constipation may be organic or functional (Causes of Constipation).
In many patients, constipation is associated with sluggish movement
of stool through the colon. This delay may be due to drugs, organic
conditions, or a disorder of defecatory function (ie, pelvic floor
dysfunction), or a disorder that results from diet (see Table: Foods
Often Affecting GI Function). Patients with disordered defecation do
not generate adequate rectal propulsive forces, do not relax the
puborectalis and the external anal sphincter during defecation, or
both. In IBS, patients have symptoms (eg, abdominal discomfort and
altered bowel habits) but generally normal colonic transit and
anorectal functions. However, IBS-disordered defecation may
coexist.

2. Excessive straining, perhaps secondary to pelvic floor dysfunction,
may contribute to anorectal pathology (eg, hemorrhoids, anal
fissures, and rectal prolapse) and possibly even to syncope. Fecal
impaction, which may cause or develop from constipation, is also
common among elderly patients, particularly with prolonged bed rest
or decreased physical activity. It is also common after barium has
been given by mouth or enema.
Causes of Constipation
Causes Examples
Acute constipation*
Bowel obstruction Volvulus, hernia, adhesions, fecal impaction
Adynamic ileus Peritonitis, major acute illness (eg, sepsis), head or spinal trauma, bed rest
Drugs
Anticholinergics (eg, antihistamines, antipsychotics, antiparkinsonian drugs, antispasmodics), cations (iron,
aluminum, Ca, barium, bismuth), opioids, Ca channel blockers, general anesthetics
Constipation shortly after start of therapy with the drug
Chronic constipation*
Colonic tumor Adenocarcinoma of sigmoid colon
Metabolic disorders Diabetes mellitus, hypothyroidism, hypocalcemia or hypercalcemia, pregnancy, uremia, porphyria
CNS disorders Parkinson disease, multiple sclerosis, stroke, spinal cord lesions
Peripheral nervous
system disorders
Hirschsprung disease, neurofibromatosis, autonomic neuropathy
Systemic disorders Systemic sclerosis, amyloidosis, dermatomyositis, myotonic dystrophy
Functional disorders Slow-transit constipation, irritable bowel syndrome, pelvic floor dysfunction (functional defecatory disorders)
Dietary factors Low-fiber diet, sugar-restricted diet, chronic laxative abuse

3. Causes Examples
*There is some overlap between acute and chronic causes of constipation. In particular, drugs are common causes of chronic
constipation.
Foods Often Affecting GI Function
Foods Likely to Cause Loose Bowel Movements and/or Excessive Gas
All caffeine-containing beverages especially coffee with chicory
Peaches, pears, cherries, apples
Fruit juices: Orange, cranberry, apple
Asparagus and cruciferous vegetables such as broccoli, cauliflower, cabbage, and Brussels sprouts
Bran cereal, whole wheat bread, high-fiber foods
Pastry, candy, chocolate, waffle syrup, doughnuts
Wine (> 3 glasses in susceptible people)
Milk and milk products (in lactose-sensitive people)
Foods Likely to Cause Constipation or Help Control Loose Bowel Movements
Rice, bread, potatoes, pasta
Meat, veal, poultry, fish
Cooked vegetables
Bananas

4. Evaluation.
History
History of present illness should ascertain a lifetime history of
the patient’s stool frequency, consistency, need to strain or use
perineal maneuvers (eg, pushing on the perineum, gluteal region, or
recto-vaginal wall) during defecation, and satisfaction after defecation
should be obtained, including frequency and duration of laxative or
enema use. Some patients deny previous constipation but, when
questioned specifically, admit to spending 15 to 20 min per bowel
movement. The presence, amount, and duration of blood in the stool
should also be elicited.
Review of systems should seek symptoms of causative disorders,
including a change in caliber of the stool or blood in the stool
(suggesting cancer). Systemic symptoms suggesting chronic
diseases (eg, weight loss) should also be sought.
Past medical history should ask about known causes, including
previous abdominal surgery and symptoms of metabolic (eg,
hypothyroidism, diabetes mellitus) and neurologic (eg, Parkinson
disease, multiple sclerosis, spinal cord injury) disorders. Prescription
and nonprescription drug use should be assessed, with specific
questioning about anticholinergic and opioid drugs.
Physical examination
A general examination is done to look for signs of systemic disease, including fever
and cachexia. Abdominal masses should be sought by palpation. A rectal examination
should be done not only for fissures, strictures, blood, or masses (including fecal
impaction) but also to evaluate anal resting tone (the puborectalis “lift” when patients
squeeze the anal sphincter), perineal descent during simulated evacuation, and rectal
sensation. Patients with defecatory disorders may have increased anal resting tone (or
anismus), reduced (ie, < 2 cm) or increased (ie, > 4 cm) perineal descent, and/or
paradoxical contraction of the puborectalis during simulated evacuation.
Red flags
Certain findings raise suspicion of a more serious etiology of chronic constipation:

5. • Distended, tympanitic abdomen
• Vomiting
• Blood in stool
• Weight loss
• Severe constipation of recent onset/worsening in elderly patients
Interpretation of findings
Certain symptoms (eg, a sense of anorectal blockage, prolonged or
difficult defecation), particularly when associated with abnormal (ie,
increased or reduced) perineal motion during simulated evacuation,
suggest a defecatory disorder. A tense, distended, tympanitic
abdomen, particularly when there is nausea and vomiting, suggests
mechanical obstruction.
Patients with IBS typically have abdominal pain with disordered
bowel habits (see Irritable Bowel Syndrome (IBS)). Chronic
constipation with modest abdominal discomfort in a patient who has
used laxatives for a long time suggests slow-transit constipation.
Acute constipation coincident with the start of a constipating drug in
patients without red flag findings suggests the drug is the cause.
New-onset constipation that persists for weeks or occurs
intermittently with increasing frequency or severity, in the absence of
a known cause, suggests colonic tumor or other causes of partial
obstruction. Excessive straining or prolonged or unsatisfactory
defecation, with or without anal digitation, suggests a defecatory
disorder. Patients with fecal impaction may have cramps and may
pass watery mucus or fecal material around the impacted mass,
mimicking diarrhea (paradoxic diarrhea).
Testing
Testing is guided by clinical presentation and the patient's diet
history.
Constipation with a clear etiology (drugs, trauma, bed rest) may be
treated symptomatically without further study. Patients with

6. symptoms of bowel obstruction require flat and upright abdominal x-
rays, possibly a water-soluble contrast enema to evaluate for colonic
obstruction, and possibly a CT scan or barium x-ray of the small
intestine (see also Intestinal Obstruction : Diagnosis). Most patients
without a clear etiology should have sigmoidoscopy or colonoscopy
and a laboratory evaluation (CBC, thyroid-stimulating hormone,
fasting glucose, electrolytes, and Ca).
Further tests are usually reserved for patients with abnormal findings
on the previously mentioned tests or who do not respond to
symptomatic treatment. If the primary complaint is infrequent
defecation, colonic transit times should be measured with radiopaque
markers (Sitz markers) or scintigraphy. If the primary complaint is
difficulty with defecation, anorectal manometry and rectal balloon
expulsion should be assessed. In patients with chronic constipation, it
is important to distinguish between slow-transit constipation
(abnormal Sitz marker radiopaque study) and pelvic floor muscle
dysfunction (markers retained only in distal colon).
Treatment
• Possibly discontinuation of causative drugs (some may be
necessary)
• Increase in dietary fiber
• Possibly trial with a brief course of osmotic laxatives
Any identified conditions should be treated.
Agents used to treat constipation are summarized in Agents Used to
Treat Constipation. Laxatives should be used judiciously. Some (eg,
phosphate, bran, cellulose) bind drugs and interfere with absorption.
Rapid fecal transit may rush some drugs and nutrients beyond their
optimal absorptive locus. Contraindications to laxative and cathartic
use include acute abdominal pain of unknown origin, inflammatory
bowel disorders, intestinal obstruction, GI bleeding, and fecal
impaction.

7. Diet and behavior
The diet should contain enough fiber (typically 15 to 20 g/day) to
ensure adequate stool bulk. Vegetable fiber, which is largely
indigestible and unabsorbable, increases stool bulk. Certain
components of fiber also absorb fluid, making stools softer and
facilitating their passage. Fruits and vegetables are recommended
sources, as are cereals containing bran. Fiber supplementation is
particularly effective in treating normal-transit constipation but is not
very effective for slow-transit constipation or defecatory disorders.
Behavioral changes may help. Patients should try to move their
bowels at the same time daily, preferably 15 to 45 min after
breakfast, because food ingestion stimulates colonic motility. Initial
efforts at regular, unhurried bowel movements may be aided by
glycerin suppositories.
Explanation is important, but it is difficult to convince obsessive-
compulsive patients that their attitude toward defecation is abnormal.
Physicians must explain that daily bowel movements are not
essential, that the bowel must be given a chance to function, and that
frequent use of laxatives or enemas (>once/3 days) denies the bowel
that chance.
Agents Used to Treat Constipation
Agent Dosage Some Adverse Effects
Fiber*
Bran Up to 1 cup/day Bloating, flatulence, iron and Ca malabsorption
Psyllium Up to 10–15 g/day in divided doses of
2.5–7.5 g
Bloating, flatulence
Methylcellulose Up to 6–9 g/day in divided doses of 0.45–
3 g
Less bloating than with other fiber agents
Ca polycarbophil 2–6 tablets/day Bloating, flatulence

8. Agent Dosage Some Adverse Effects
Emollients
Docusate Na 100 mg bid or tid Ineffective for severe constipation
Glycerin 2–3 g suppository once/day Rectal irritation
Mineral oil 15–45 mL po once/day Lipid pneumonia, malabsorption of fat-soluble vitamins, dehydration, fecal
incontinence
Osmotic agents
Sorbitol
15–30 mL po of 70% solution once/day or
bid
120 mL rectally of 25–30% solution
Transient abdominal cramps, flatulence
Lactulose 10–20 g (15–30 mL) once/day up to qid Same as for sorbitol
Polyethylene glycol 17 g daily Fecal incontinence (related to dosage)
Mg
MgCl2 or Mg sulfate tablets 1–3 g qid
Milk of Mg 30–60 mL/day
Mg citrate 150–300 mL/day (up to 360
mL)
Mg toxicity, dehydration, abdominal cramps, fecal incontinence, diarrhea
Na phosphate 10 g po once as bowel preparation Rare cases of acute renal failure
Stimulants
Anthraquinones Depends on brand used Abdominal cramps, dehydration, melanosis coli, malabsorption, possible
deleterious effects on intramural nerves
Bisacodyl
10-mg suppositories up to 3 times/wk
5–15 mg/day po
Fecal incontinence, hypokalemia, abdominal cramps, rectal burning with daily
use of suppository form

9. Agent Dosage Some Adverse Effects
Linaclotide 145–290 mcg po once/day at least 30 min
before first meal
Abdominal pain, flatulence Contraindicated in children < 6 yr; avoided in
children < 17 yr
Lubiprostone†
24 mcg po bid with food Nausea, particularly on empty stomach
Enemas
Mineral oil/olive oil
retention
100–250 mL/day rectally Fecal incontinence, mechanical trauma
Tap water 500 mL rectally Mechanical trauma
Phosphate 60 mL rectally Accumulated damage to rectal mucosa, hyperphosphatemia, mechanical
trauma
Soapsuds 1500 mL rectally Accumulated damage to rectal mucosa, mechanical trauma
*The dose of fiber supplements should be gradually increased over several weeks to the recommended dose.
†
Lubiprostone is available by prescription only and is approved for long-term use.
Adapted from Romero Y, Evans JM, Fleming KC, Phillips SF: Constipation and fecal incontinence in the elderly population. Mayo Clinic
Proceedings 71:81–92, 1996; by permission.
Types of laxatives
Bulking agents (eg, psyllium, Ca polycarbophil, methylcellulose)
act slowly and gently and are the safest agents for promoting
elimination. Proper use involves gradually increasing the dose—
ideally taken tid or qid with sufficient liquid (eg, 500 mL/day of extra
fluid) to prevent impaction—until a softer, bulkier stool results.
Bloating may be reduced by gradually titrating the dose of dietary
fiber to the recommended dose, or by switching to a synthetic fiber
preparation such as methylcellulose.

10. Osmotic agents contain poorly absorbed polyvalent ions (eg, Mg,
phosphate, sulfate), polymers (eg, polyethylene glycol), or
carbohydrates (eg, lactulose, sorbitol) that remain in the bowel,
increasing intraluminal osmotic pressure and thereby drawing water
into the intestine. The increased volume stimulates peristalsis. These
agents usually work within 3 h.
In general, osmotic laxatives are reasonably safe even when used
regularly. However, Na phosphate should not be used for bowel
cleansing because it may rarely cause acute renal failure even after a
single use for bowel preparation. These events occurred primarily in
elderly patients, those with preexisting renal disease, and those who
were taking drugs that affect renal perfusion or function (eg, diuretics,
ACE inhibitors, angiotensin II receptor blockers). Also, Mg and
phosphate are partially absorbed and may be detrimental in some
conditions (eg, renal insufficiency). Na (in some preparations) may
exacerbate heart failure. In large or frequent doses, these drugs may
upset fluid and electrolyte balance. Another approach to cleansing
the bowel for diagnostic tests or surgery or sometimes for chronic
constipation uses large volumes of a balanced osmotic agent (eg,
polyethylene glycol–electrolyte solution) given orally or via NGT.
Secretory or stimulant cathartics (eg,
phenolphthalein, bisacodyl, anthraquinones, castor oil,
anthraquinones) act by irritating the intestinal mucosa or by directly
stimulating the submucosal and myenteric plexus. Although
phenolphthalein was withdrawn from the US market after animal
studies suggested the compound was carcinogenic, there is no
epidemiologic evidence of this in humans. Bisacodylis an effective
rescue drug for chronic constipation. The anthraquinones senna,
cascara sagrada, aloe, and rhubarb are common constituents of
herbal and OTC laxatives. They pass unchanged to the colon where
bacterial metabolism converts them to active forms. Adverse effects
include allergic reactions, electrolyte depletion, melanosis coli, and
cathartic colon. Melanosis coli is a brownish black colorectal
pigmentation of unknown composition. Cathartic colon refers to
alterations in colonic anatomy observed on barium enema in patients
with chronic stimulant laxative use. It is unclear whether cathartic
colon, which has been attributed to destruction of myenteric plexus

11. neurons by anthraquinones, is caused by currently available agents
or other neurotoxic agents (eg, podophyllin), which are no longer
available. There does not seem to be an increased risk of colon
cancer with long-term anthraquinone use.
Enemas can be used, including tap water and commercially
prepared hypertonic solutions.
Emollient agents (eg, docusate, mineral oil) act slowly to soften
stools, making them easier to pass. However, they are not potent
stimulators of defecation. Docusate is a surfactant, which allows
water to enter the fecal mass to soften and increase its bulk.
Fecal impaction
Fecal impaction is treated initially with enemas of tap water followed by small
enemas (100 mL) of commercially prepared hypertonic solutions. If these do not
work, manual fragmentation and disimpaction of the mass is necessary. This
procedure is painful, so perirectal and intrarectal application of local anesthetics
(eg, lidocaine 5% ointment or dibucaine 1% ointment) is recommended. Some
patients require sedation.
Geriatrics Essentials
Constipation is common among elderly people because of low-fiber diets, lack of
exercise, coexisting medical conditions, and use of constipating drugs. Many elderly
people have misconceptions about normal bowel habits and use laxatives regularly.
Other changes that predispose the elderly to constipation include increased rectal
compliance and impaired rectal sensation (such that larger rectal volumes are needed
to elicit the desire to defecate).
Key Points
• Drug causes are common (eg, chronic laxative abuse, use of anticholinergic or
opioid drugs).
• Be wary of bowel obstruction when constipation is acute and severe.
• Symptomatic treatment is reasonable in the absence of red flag findings and
after excluding pelvic floor dysfunction.

12. DYSCHEZIA
(Disordered Evacuation; Dysfunction of Pelvic Floor or Anal Sphincters; Functional
Defecatory Disorders; Dyssynergia)
Dyschezia is difficulty defecating. Patients sense the presence of stool and the need to
defecate but are unable. It results from a lack of coordination of pelvic floor muscles
and anal sphincters. Diagnosis requires anorectal testing. Treatment is difficult, but
biofeedback may be of benefit.
Etiology
Normally, when a person tries to defecate, rectal pressure rises in coordination with
relaxation of the external anal sphincter. This process may be affected by one or more
dysfunctions (eg, impaired rectal contraction, excessive contraction of the abdominal
wall, paradoxic anal contraction, failure of anal relaxation) of unclear etiology.
Functional defecatory disorders may manifest at any age. In contrast, Hirschsprung
disease, which is due to an absent recto-anal inhibitory reflex, is almost always
diagnosed in infancy or childhood.
Symptoms and Signs
The patient may or may not sense that stool is present in the rectum. Despite
prolonged straining, evacuation is tedious or impossible, frequently even for soft stool
or enemas. Patients may complain of anal blockage and may digitally remove stool
from their rectum or manually support their perineum or splint the vagina to evacuate.
Actual stool frequency may or may not be decreased.
Diagnosis
Rectal and pelvic examinations may reveal hypertonia of the pelvic floor muscles and
anal sphincters. With bearing down, patients may not demonstrate the expected anal
relaxation and perineal descent. With excessive straining, the anterior rectal wall
prolapses into the vagina in patients with impaired anal relaxation; thus rectoceles are
usually a secondary rather than a primary disturbance. Long-standing dyschezia with
chronic straining may cause a solitary rectal ulcer or varying degrees of rectal
prolapse or excessive perineal descent or an enterocoele. Anorectal manometry and
rectal balloon expulsion, occasionally supplemented by defecatory or magnetic
resonance proctography, are necessary to diagnose the condition.

13. Treatment
Because treatment with laxatives is unsatisfactory, it is important to assess anorectal
functions in patients with refractory constipation. Biofeedback therapy can improve
coordination between abdominal contraction and pelvic floor relaxation during
defecation, thereby alleviating symptoms. However, pelvic floor retraining for
defecatory disorders is highly specialized and available at select centers only. A
collaborative approach (physiotherapists, dietitians, behavior therapists,
gastroenterologists) is necessary.