Pediatric emergency medicine trisk 117

TABLE 18.4
LIFE-THREATENING CAUSES OF CONSTIPATION
Acute constipation
Mechanical obstruction
Dehydration
Infantile botulism
Chronic constipation
Hirschsprung disease
Abdominal/pelvic mass
Anorexia nervosa
Cystic fibrosis
Hirschsprung disease, or congenital intestinal aganglionosis, is rare (1 in 5,000
live births with a 4:1 male to female predominance) but must be considered in the
constipated infant because it has the potential to cause life-threatening
complications. The distal aganglionic segment remains tonically contracted while
the segment proximal to the blockage dilates with stool buildup. This can lead to
megacolon which, in turn, can cause life-threatening Hirschsprung-associated
enterocolitis (HAEC). HAEC should be considered in any patient presenting with
fever, abdominal distention, explosive sometimes bloody stools, and vomiting in
whom Hirschsprung disease is suspected.
Of the infants with Hirschsprung disease, 80% are diagnosed within the first
year of life. A history of late passage of meconium >48 hours after birth is often
but not always noted ( Table 18.6 ). If the involved segment is relatively short,
the diagnosis may be delayed. Abdominal examination in Hirschsprung’s often
yields a palpable suprapubic mass of stool that may extend throughout the
abdomen. Rectal examination reveals a constricted anal canal with the absence of
stool in the rectal vault, commonly followed by expulsion of stool when the
finger is removed. A similar phenomenon may occur when a rectal temperature is
taken. The combination of palpable abdominal feces and an empty rectal vault is
abnormal and warrants further evaluation. Diagnosis is supported by an
unprepped barium enema showing a transition zone where the narrow distal

bowel transitions to the aganglionic dilated proximal bowel. When only a short
segment of bowel is involved, a barium enema may be falsely negative and anal
manometry may aid in the diagnosis. A negative barium enema cannot be used to


rule out the diagnosis of Hirschsprung disease. The gold standard for diagnosis,
however, remains a rectal biopsy (see also Chapter 91 Gastrointestinal
Emergencies ).

FIGURE 18.1 Approach to constipation.


TABLE 18.5
SOME MEDICATIONS ASSOCIATED WITH CONSTIPATION
Aluminum
Amiodarone
Amitriptyline
Anticholinergic agents (benztropine, glycopyrrolate, promethazine)
Antineoplastic agents (procarbazine, vincristine)
Benzodiazepines
β-Blockers
Calcium salts
Calcium channel blockers
Cholestyramine
Diazoxide
H2 receptor antagonists (ranitidine)
Iron
Mesalamine
Ondansetron
Opioids

Phenobarbital
Phenothiazines and derivatives (prochlorperazine, promethazine, haloperidol)
Phenytoin
Proton pump inhibitors
Sucralfate
Ursodiol
Other conditions that may present with constipation in infancy or early
childhood include hypothyroidism, water-losing disorders such as diabetes
insipidus, renal tubular acidosis, and cystic fibrosis. Cystic fibrosis can present
with constipation alone. When there is a history of delayed passage of meconium
and once Hirschsprung disease has been ruled out, evaluation for cystic fibrosis
by a sweat test or genetic testing is indicated.


TABLE 18.6
FINDINGS IN HIRSCHSPRUNG DISEASE AND FUNCTIONAL
CONSTIPATION
Onset in infancy (<1 mo)
Delayed passage of meconium (>48
hrs)
Painful defecation
Stool-withholding behavior
Soiling
Stool in rectal vault
Failure to thrive
Bilious vomiting

Hirschsprung’s

Functional

Common
Common

Rare
Rare

Rare
Rare
Rare
Rare
Common
Common

Common
Common
Common
Common
Rare
Rare

Chronic constipation in the older child ≥6 months of age overwhelmingly is
caused by functional constipation. Typically, a cycle of stool withholding starts
when the child disregards the signal to defecate and strikes a retentive posture,
rising on the toes and stiffening the legs and buttocks. This maneuver forces the
stool back into the rectum, which subjects the fecal bolus to further water
absorption and enlargement leading to painful and traumatic defecation. This
reinforces stool-withholding behavior. Over time, the rectum dilates and sensation
to stool diminishes. Eventually, the child loses the urge to defecate altogether.
Eventually, watery stool starts to leak around the large fecal mass causing

involuntary soiling or encopresis. This may be misconstrued as diarrhea or as
regression in the toilet-trained child. Many parents consult a physician at this
point. Other reasons parents seek medical attention are abdominal pain, anorexia,
vomiting, and irritability.
The most common timing for functional constipation to develop is when
routines change such as during toilet training and upon starting school. At school,
play time may distract a child from the signal to defecate. Painful defecation from
streptococcal perianal disease or sexual abuse must be also be considered in
patients with stool withholding. Functional constipation can also be associated
with dysfunctional urinary voiding and recurrent urinary tract infections.
A history supportive of functional constipation includes retentive posturing,
infrequent passage of very large stools, and involuntary soiling. Physical