A 4-year-old boy presents with a history of constipation since the age of 6 months. His stools, produced every 3 to 4 days, are described as large and hard. His growth velocity is normal. Physical examination is normal; 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. Which of the following is the most appropriate next step in the management of this child?

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.