The Gastrointestinal Tract
A 4-year-old boy is seen by the pediatrician with the parental complaint of constipation since the child was about 6 months old. The family reports that he produces "large and hard" stools every 3-4 days. They deny nausea, vomiting, fever, change in behavior, or blood in his stools. He was born at term by planned repeat cesarean section, voided and stooled in the first day of life, and was discharged to home on the third day of life. Subsequently he has been a healthy child without serious illnesses; he does well in pre-K programs. He takes no medications and his immunizations are current. On physical examination the vital signs are normal. The weight is at the 75th percentile, the length at the 65th percentile, and the head circumference at the 75th percentile for age. The mucous membranes are pink, moist, and without lesions. The chest is clear. Heart has a normal S1 and S2 without murmur. The abdomen is somewhat full but soft and nontender. No hepatosplenomegaly or adenopathy is noted. Rectal examination reveals a large ampulla, poor sphincter tone but present anal wink, and stool in the rectal vault. The plain film of his abdomen is shown (Photograph). Which of the following is the most appropriate next step in management?
a. Obtain a lower gastrointestinal (GI) barium study
b. Provide parental reassurance and dietary counseling
c. Measure serum electrolyte measurement
d. Order an upper GI barium study
e. Initiate thyroid-replacement hormone
(Courtesy of Susan John, MD.)
The answer is b. (Hay et al, pp 670-672. Kliegman et al, pp 1245-1247, 1284-1287. McMillan et al, pp 373-375, 1920-1923. Rudolph et al, pp 1386-1389, 1436-1437.) This child has a normal past history and normal growth. The radiograph demonstrates a stool-filled megacolon. Finding a dilated, stool-filled anal canal with poor tone on the physical examination of a well-grown child supports the diagnosis of functional constipation. Hirschsprung disease is usually suspected in the chronically constipated child despite the vast majority of such children having functional constipation. The treatment of functional constipation, once it has been established as the diagnosis, emphasizes dietary changes and counseling of parents regarding proper toileting behavior. Effective stool softeners are available as a second line option. An extensive workup of this patient would likely be negative and expensive, and is not indicated. Hirschsprung usually presents in infancy with increasingly difficult defecation in the first few weeks of life. Typically no stool is found in the rectum, and anal sphincter tone is abnormal. Diagnosis of Hirschsprung disease may be made with rectal manometry and rectal biopsy.