Things We Do for No Reason™: Obtaining an Abdominal X-ray to Assess for Constipation in Children

Functional constipation is a clinical diagnosis based on a thorough collection of history and a complete physical exam in children of all ages, including digital examination of the rectum to assess for fecal impaction, if necessary.

The Rome IV criteria for chronic constipation can be helpful and includes at least 2 of the following features for at least 1 month in infants up to 4 years of age: 2 or fewer stools per week, history of excessive stool retention, history of painful or hard bowel movements, history of large-diameter stools, and presence of a large fecal mass in the rectum.¹³ In children who are toilet trained, 2 additional criteria may be used: at least 1 episode of fecal incontinence per week after being toilet-trained and history of large-diameter stools that may obstruct the toilet.¹³

The NASPGHAN and ESPGHAN joint guidelines from 2014 state that, while constipation is based on history and physical exam, a major role of the history and physical exam is to exclude other disorders that also present with difficulty in defecation.⁸ This can help identify red-flag features or complications and guide further investigation. While evidence did not support routine use of a digital rectal exam in diagnosing constipation, the guidelines stated that a rectal exam (visual and digital) helps to evaluate for anorectal malformations, anal stenosis, rectal tone, distension, erythema, skin tags, anal fissures, or a fecal mass.⁸ Digital rectal exams may be helpful in patients who do not immediately meet at least 2 historical features of the Rome IV criteria.

In regard to history, approximately 0.4%-20% of healthy children without constipation have at least 1 clinical feature listed above. Therefore, the use of a single clinical finding to diagnose constipation, such as decreased bowel frequency, can result in an inappropriate diagnosis. Children experience large variations in stool output depending on diet, genetics, and environmental factors.¹⁰ The usual pattern of bowel habits in humans range from 3 times daily to every 3 days.¹⁴ Importantly, there are times to order an abdominal x-ray for patients with abdominal pain. The NASPGHAN and ESPGHAN joint guidelines recommend obtaining abdominal x-rays to evaluate children who have concerning features, such as previous abdominal surgeries, known genetic conditions or malformations, bilious emesis, or severe abdominal distension.⁸

• Functional constipation should be diagnosed based purely on a thorough history and physical examination, including a rectal exam
• Abdominal x-rays (ordered for any reason) should not be used to diagnose or assess for functional constipation

Performing abdominal x-rays to assess for pediatric functional constipation is not beneficial and potentially harmful to patients. Multiple retrospective studies revealed no diagnostic association between clinical symptoms or severity of constipation and findings on abdominal radiography. X-rays have very low sensitivity and specificity for diagnosing constipation. In the pediatric emergency department, abdominal x-rays completed for patients diagnosed with constipation have been associated with missed diagnoses, false reassurance of constipation, more frequent admissions into the hospital, longer hospital stays, higher healthcare costs, and unnecessary radiation exposure. The NICE as well as 2014 NASPGHAN and ESPGHAN clinical guidelines recommend against obtaining x-rays to diagnose constipation. The most effective way to diagnose functional constipation in children is with a thorough collection of history and physical exam. In the introductory case, the boy received an osmotic laxative based on abdominal x-ray findings, which resulted in the adverse effect of diarrhea. This case demonstrates how using abdominal x-rays to assess for constipation can be misleading and emphasizes the importance of collecting a thorough history and physical exam.