You don’t need an X-Ray to diagnose constipation! (Re-post)

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:

Infants and toddlers

  • 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

Children 4 to 18 years of age

  • 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.

  1. If you are worried about a bowel obstruction
  2. A child has a past medical history of surgery inside their belly and presents with a new complaint of constipation
  3. 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.

From Life in the Fastlane

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.

Do we need to perform a digital rectal exam in injured children?

If you work in a trauma center you will see injured children. Most of the serious injuries to children are blunt. Diagnostic workup often includes labs and imaging – but begins with a focused physical assessment underpinned by ATLS. The digital rectal exam can help assess for rectal tone in spinal cord injuries and gross blood in bowel injuries and thus, in severely injured children (think GCS <8) is a no-brainer. For others however, it can be invasive and downright scary. I was wondering whether or not it was absolutely necessary to perform a rectal exam would add any diagnostic utility. Let’s take a look at two studies shall we?

Lack of evidence to support routine digital rectal examination in pediatric trauma patients

Shlamovitz GZ. Mower WR. Bergman J. Crisp J. DeVore HK. Hardy D. Sargent M. Shroff SD. Snyder E. Morgan MT.
Pediatric Emergency Care Aug 2007; 23(8): 537-43

Shlamovitz et al conducted an observational chart review study to identify DRE findings followed by radiologic and operative reports, and discharge summaries to identify specific injuries. They noted the following:

  • Detection of spinal cord injury by decreased anal sphincter tone 33% sensitive (95% CI 6-79%) and 99% specific (95% CI 96-100%)
  • Presence of gross blood to diagnose bowel injuries on exam was 0% sensitive (95% CI 0-23%)
    and 98% specific (95% CI 95-99%)
  • Palpation of disrupted rectal wall integrity was 0% sensitive (95% CI 0-65%) and 100% specific 95% (95% CI 95-100%)
  • Palpation of bony fragments on exam to diagnose pelvic fracture 0% sensitive (95% CI 0-65%) and 100% specific (95% CI 95-100%)
  • Diagnosis of urethral injury by presence of abnormal position (high-riding) of prostate was 0% sensitive (95% CI 0-79%) and 100% specific  (95% CI 94-100)

So, it would seem that this study would lead us to conclude that the DRE can help “rule-in” injuries. But, it also relied on chart review, which is prone to missing data, was conducted at a Level 1 Trauma Center (not the place where most kids go after being injured), there was no blinding to results, no mention of interrupter reliability (which would I suppose require two DREs) and rectal exam was either deferred or not even recorded in a third of patients. Furthermore, the ethical issues were not addressed.

The digital rectal examination in pediatric trauma: A pilot study

Kristinsson G. Wall SP. Crain EF.
Journal of Emergency Medicine Vol. 32, No. 1, pp. 59–62, 2007

Kristinsson et al. conducted a pilot study of children 1-17 years to evaluate the utility of DRE to identify injuries by comparing physical exam during the secondary survey with and without rectal exam. Note that the majority of patients in this study were NOT comatose/obtunded (the mean GCS was 15) and that there weren’t many DRE identifiable injuries to begin with. This, statistically speaking, has the effect of widening the confidence intervals quite a bit. Nevertheless, here is what the authors noted:

  • Physical exam with DRE for detecting injury 87.5% sensitive (95%CI 47.3-99.7%)
    and 78.7% specific (95%CI 70.6-85.5%)
  • Physical exam without DRE for detecting injury 87.5% sensitive (95% CI 47.3-99.7%)
    and 87.4% specific (95% CI 80.3-92.6%)

Overall, these numbers need to be interpreted in the face of low injury prevalence and relatively well patients.

Let’s start with the fact that DRE isn’t necessarily evidence based in trauma. Even with prep from child life or other support personnel the rectal exam is traumatic for the child who was just strapped to a backboard and is still confined to a cervical collar, often surrounded by multiple people they don’t know. Overall these studies indicate that DRE isn’t necessarily accurate in children and a “false positive” result could expose kids to unnecessary CTs. Furthermore, in the very injuries obtunded child would a “negative” DRE really stop you from enacting spinal precautions and obtained advanced imaging? Overall, DRE likely has very limited utility in injured children. It should really be reserved for children with the following features:

  • Penetrating trauma near the rectum
  • Children with an obvious pelvic fracture
  • When spinal cord injury and spinal shock cant be excluded based on the exam
  • Those sick enough to be intubated and sedated (GCS ≤8-9)

Otherwise, for most kids with blunt trauma there isn’t enough justification. Anecdotally, I see the exam initiated by surgery most often. Thus, I recommend first and foremost you have a discussion with local personnel and make yourself aware of institutional practices.

Check out this new free PEM iBook

PEM (Pediatric Emergency Medicine) Guides was spearheaded by Dr. Michael Mojica as a point of care resource in the pediatric emergency departments at Bellevue Hospital Center and NYU Langone Medical Center. The focus is in essential diagnostic, treatment and disposition decisions and though not a definitive resource it does have concise and easily accessible information for a wide number of conditions in the Pediatric Emergency Department. And, besides, the price is right, and it will continue to be updated unlike those books printed on paper.

Check it out herecover225x225

 

Stress dose steroids in the ED

Came across this great post on Academic Life in Emergency Medicine from Drs. Delhine Huang and Sony Tat recently that was too good not to share here as well. I’ve always been slightly vexed by stress dose steroids in the ED. Here are some take home points followed by the embedded video.

Who needs them?

Any patient on chronic steroids, Addison’s disease, or something wrong with their hypothalamic/pituitary axis and are sick. Recall that the daily “physiologic” dose of hydrocortisone is hydrocortisone is 6-12 mg/m2/day. Many children will be on chronic daily steroids – commonly prednisone and hydrocortisone. In general 5mg of prednisone is roughly equivalent to 20mg of hydrocortisone. For trivia’s sake 0.75mg of dexamethasone equals 5mg of prednisone.

How much do I give?

I really like the simplified version from ALiEM – they call it the “coin method”

  • For small-sized kids (neonates to 3 years old), give 25 mg IV/IM (or think of a quarter)
  • For medium-sized kids (3-12 years old), give 50 mg IV/IM (or think of a half-dollar)
  • For large-sized kids (12+ years old), give 100 mg IV/IM (or think of a dollar coin)

How do I calculate the body surface area on a sick child?

Use an online calculator, ask the parent for height, or just estimate – remember you are giving steroids to prevent/treat adrenal crisis in the face of a serious illness. Plus, this is #Merica so MOAR IS BETTER! No one will fault you for giving a higher single dose of a steroid for a child in crisis. More precise adjustments can be made after initial stabilization.