Diagnosis and Misdiagnosis of Constipation

A personal pet peeve is having to explain to so many parents that their child is not constipated.  The typical scenario is that their child went to the ER for abdominal pain and had an abdominal radiograph (AXR); then, the parents are informed that their child is constipated based on ‘fecal loading’ noted on the AXR.  In this scenario, it is common for the child to have the following:

  • regular bowel movements
  • lack of a rectal exam
  • lack of improvement with laxatives (though some do improve, perhaps due to the fact that symptoms often have regression to the mean)
  • often a normal AXR when interpreted by radiologist rather than ED physician (it is normal to have some stool in the colon)

So, I like to see publications that support my viewpoint that this approach is misguided. Two recent studies provide some insight into this topic:

  • SB Freedman et al. J Pediatr 2017; 186: 87-94
  • CC Ferguson et al. Pediatrics 2017; 140 (1):e20162290 (thanks to Ben Gold for this reference)

Freedman et al performed a retrospective cohort study (children <18 yrs) who were diagnosed with constipation at 23 EDs from 2004-2015. This study used the PHIS database. Key findings:

  • 185,439 of 282,225 had AXR at index ED visit
  • Revisits to ED occurred in 3.7%
  • 0.28% returned with a clinically important alternate diagnosis, most commonly appendicitis (34% in this category)
  • Children who had AXR were more likely to have a 3-day revisit with a clinically important alternate diagnosis (0.33% vs. 0.17%)

Recognizing that AXRs are “unnecessary and potentially misleading,” Ferguson et al aimed to decrease AXR utilization in low-acuity patients who were suspected of having constipation. Using quality tools, the authors performed four plan-do-study-act cycles which included holding grand rounds, sharing best practices, metrics reporting, and academic detailing. Key finding:

  • Over 12 months, we observed a significant and sustained decrease from a mean rate of 62% to a mean rate of 24% in the utilizaiton of AXRs in the ED for patients suspected of having constipation.

My take: These studies support my view that routine use of AXR in the diagnosis of constipation is a mistake and can be misleading.

Related blog posts:

2 thoughts on “Diagnosis and Misdiagnosis of Constipation

  1. I completely agree that KUBs are pretty much worthless in constipation eval. To be charitable, maybe EDs like them to rule out an appendolith or kidney stone, or fluid levels that suggest obstruction? Probably not — there are better ways to eval for those things, too.

    But I’m not entirely convinced, at least in my experience as a generalist, that a rectal exam is useful for routine eval, either. Maybe you GI folk do more of them, and get more information out of them. But I’m afraid of the dark, and don’t find them particularly helpful.

    • In patients that I see, a rectal exam is helpful. Besides getting a sense that everything is in ‘working order,’ it gives the best indication of whether a cleanout is needed at the start of therapy.

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