I’m not really going out on a limb when I say that constipation is a common diagnosis in the pediatric emergency department. Now, that being said, not all patients that have a diagnosis of constipation are actually constipated. I have certainly seen scenarios where parents have been told that their child is constipated as an explanation for belly pain when the history is actually not that suggestive. Some of these patients even got an X-Ray. And this radiograph is what was used to diagnose them with constipation. Many of you may be familiar with the following Radiology read:
Nonobstructive bowel gas pattern, moderate stool burden
What does that actually mean if the kid poops every day? So the purpose of this post is two fold. One, let’s actually review what it takes to diagnose a patient with constipation, and two, talk about when an X-ray should be used to help you make that diagnosis.
Diagnosis
When we talk about constipation, we are generally referring to the entity known as “functional constipation,” which requires two out of the following six criteria:
- Two or fewer defecations per week
- At least one episode of incontinence after the acquisition of toileting skills
- History of excessive stool retention
- History of painful or hard bowel movements
- Presence of a large fecal mass in the rectum
- History of large-diameter stools that may obstruct the toilet
- Two or fewer defecations per week
- At least one episode of fecal incontinence per week
- History of retentive posturing or excessive volitional stool retention
- History of painful or hard bowel movements
- Presence of a large fecal mass in the rectum
- History of large-diameter stools that may obstruct the toilet
The aforementioned symptoms are from the Rome III criteria for the diagnosis of functional constipation. Additionally, it is important to note that four out of five patients with constipation will have some degree of fecal incontinence in the face of functional constipation. So, ask about encopresis.
Before moving on to the X-Ray portion of this post, I want you to consider the following statistic:
Fewer than 1/20 of children with constipation have an organic cause
Check out Di Lorenzo and this article from Peds in Review for more. In general, an organic cause specifies that something is preventing the patient from pooping. A bowel obstruction is the most serious one to recognize in the ED. A special-case is the infant under the age of 6 months with dyschezia, which is defined as at least 10 minutes of straining and crying before successful passage of soft stools in an otherwise healthy infant. Parents will describe a baby that their otherwise healthy infant cries and gets all red in the face for 20 minutes before having a bowel movement. they will be concerned about constipation. babies with dyschezia have not yet learned how to coordinate the relaxation of the pelvic floor with Valsalva. Treatment includes reassurance alone. Digital stimulation and suppositories can do more harm than good.
X-Rays
OK, so when should an X-Ray be ordered. Well, let me keep it simple.
- If you are worried about a bowel obstruction
- A child has a past medical history of surgery inside their belly and presents with a new complaint of constipation
- Children in whom the diagnosis of constipation is equivocal despite a thorough history and physical exam
Other situations where an X-Ray might be helpful include situations where a baby did not have a bowel movement within the first 24 hours of life. Failure to pass meconium in this time period raises concerns for short segment Hirschsprung’s and distal intestinal obstruction syndrome (DIOS) in Cystic Fibrosis. You may also consider an Xray if you are worried about a swallowed foreign body, thought these are more likely to present with pain. Children that have ingested a lot of elemental iron or lead (vitamins, PICA) can be constipated, and X-Rays can show train tracking of pills in the gut.
Let’s face it – Plain radiographs are just not that sensitive for constipation. Berger et al in J Pediatrics found in their systematic review that “the sensitivity of abdominal radiography, as studied in 6 studies, ranged from 80% (95% CI, 65-90) to 60% (95% CI, 46-72), and its specificity ranged from 99% (95% CI, 95-100) to 43% (95% CI, 18-71).” They can also be interpreted inconsistently at best. Pensabene et al in J Pediatr Gastroenterol Nutr, 2010 noted that various radiographic scores all had low discriminative value and inter observer reliability.
Finally, it is important to address parent expectations. Many place inherently more trust in objective data and interventions. They can believe that a doctor needs to “do something” or “run some tests” in order to make a diagnosis. Getting an X-Ray to diagnose something that your history already suggests is inefficient and misuses resources. Spend more time educating and reassuring parents. This will enable you to build a therapeutic alliance, and may translate into greater knowledge and understanding of the rationale behind your therapeutic recommendations.
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