Approach to constipation (pediatrics): Clinical sciences

Constipation refers to an abnormal stooling pattern that's associated with hard stools and incomplete, infrequent, or painful defecation. The stooling pattern in healthy infants is highly variable, but when constipation occurs it suggests a pathologic condition. On the flip side, by 4 years of age, most healthy children pass one normally formed stool daily or every other day. Constipation in this age group is more likely to represent a functional gastrointestinal or GI disorder.

Now, if a pediatric patient presents with constipation, you should first obtain a focused history and physical examination. These patients or their caregivers typically report infrequent bowel movements, straining during defecation, and hard stool consistency. Meanwhile, the physical exam may demonstrate mild abdominal distension, a palpable stool mass in the lower abdomen, or an anal fissure. These findings confirm a diagnosis of constipation.

Now, here’s a clinical pearl! As part of your diagnostic workup, you can also perform a digital rectal exam to assess for impacted stool in the rectal vault. However, because it’s uncomfortable and invasive, many practitioners only perform this exam when alarm symptoms are present or when the diagnosis is unclear.

Okay, now that you know your patient has constipation, your next step is to assess their age and proceed with your diagnostic workup.

Let’s start by discussing constipation in newborns. In this age group, it’s essential to assess the timing of meconium passage. If your patient has not passed meconium within 48 hours of birth, examine your patient to assess anal patency.

Let’s start with abnormal exam findings. If your patient has an imperforate anus, meaning you cannot identify an anal opening; or if the anal opening appears stenotic or anteriorly displaced, diagnose constipation due to an anorectal malformation.

Time for a clinical pearl! Imperforate anus often occurs in combination with other congenital anomalies, as part of the VACTERL association; so be sure to look for anatomic anomalies involving the: Vertebrae, Anus, Cardiac structures, Trachea, Esophagus, Renal system, and Limbs.

Now, let’s say the exam reveals a patent anus with normal anatomy. In this case, consider conditions that cause intestinal obstruction, like meconium ileus and Hirschsprung disease; and order an abdominal X-ray.

In some cases, the X-ray might show dilated loops of small bowel with a bubbly appearance which represents meconium that's mixed with air, sometimes referred to as “soap bubble” or “ground glass” appearance. If you see it, consider meconium ileus and order a contrast enema. The presence of a microcolon with a dilated proximal bowel confirms meconium ileus, a condition in which hyperviscous meconium sticks to the small bowel wall and obstructs the terminal ileum. The majority of newborns with meconium ileus have cystic fibrosis, so remember to order a sweat chloride test for patients who fail to pass meconium within 48 hours of birth.

Okay, let’s go back to X-ray findings. If the radiograph demonstrates dilated proximal bowel loops and decreased or absent air in the distal segment of the colon; consider Hirschsprung disease. Then, obtain a contrast enema and consider a rectal suction biopsy.

In Hirschsprung disease, the enema typically shows a funnel-shaped transition zone between the dilated proximal colon and a narrow distal segment. If you obtain a biopsy, it will reveal an absence of ganglion cells in the colonic submucosa. With these findings, diagnose Hirschsprung disease.

Also remember that Hirschsprung disease commonly occurs in patients with Down syndrome, so keep a high index of suspicion in these patients, especially if they also have bilious vomiting, abdominal distension.

Now, let’s go back and consider infants who have passed meconium within 48 hours of birth. Your next steps are to assess your patient’s sacral anatomy and perform a neurologic exam. The exam might reveal a sacral dimple; a tuft of hair or pigmentation over the lower spine; as well as an absent anal wink or decreased lower extremity reflexes. These findings should make you consider the possibility of a spinal cord abnormality and obtain an MRI of the spine.

Imaging may demonstrate a meningomyelocele, a tethered spinal cord, or a spinal cord tumor; any of which confirms the presence of a spinal cord abnormality.