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 (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