Acute Abdominal Series for Pediatric Constipation
An acute abdominal series (plain abdominal radiographs) is NOT necessary and should NOT be routinely obtained for children presenting with constipation. The diagnosis of constipation is clinical, based on Rome III criteria, and imaging does not improve diagnostic accuracy or change management 1, 2.
Why Radiographs Should Be Avoided
Plain abdominal radiographs have poor diagnostic utility and can be misleading:
Systematic review evidence shows conflicting association between clinical symptoms of constipation and fecal loading on radiographs, with likelihood ratios close to 1.0 (95% CI: 0.5-1.6), meaning the test does not meaningfully change pre-test probability 2
Multiple scoring systems (Barr, Leech, fecal loading scores) demonstrate poor interobserver reproducibility and limited discriminative value, with more than 20% of children with functional constipation having normal radiograph scores 3
Radiographs increase misdiagnosis rates and involve unnecessary radiation exposure in a pediatric population already at higher risk from radiation effects 1, 4
Over 50% of children with non-retentive fecal incontinence (not true constipation) have abnormal radiograph scores, leading to inappropriate treatment 3
When Radiographs May Have Limited Utility
The ACR guidelines indicate radiographs may identify alternative causes of abdominal pain (such as constipation when evaluating for other conditions like appendicitis), but this does NOT support their use when constipation is already the suspected diagnosis 5
Reserve radiography only for:
- Intractable constipation not responding to standard therapy, where assessment by the same observer over time may track treatment response 6
- Suspected complications requiring emergent intervention (bowel perforation, obstruction) with upright or decubitus views to assess for pneumoperitoneum 7
The Correct Diagnostic Approach
Make the diagnosis clinically using Rome III criteria:
- Frequency and consistency of bowel movements
- History of painful defecation
- Presence of large fecal mass in rectum
- History of large-diameter stools 1, 4
If diagnostic uncertainty exists or complications are suspected:
- Ultrasound is the preferred initial imaging modality for children with acute abdominal pathology, offering no radiation exposure and effective detection of alternative diagnoses 8, 7
- CT with IV contrast should be reserved for cases where ultrasound is equivocal and clinical suspicion for serious pathology persists 8, 7
Common Pitfall to Avoid
The most common reason providers obtain radiographs is to "convince families" of the constipation diagnosis (44% of surveyed providers), but this is not a viable management strategy given radiation risks and costs 4. Instead, use clinical criteria and patient education to establish the diagnosis and initiate treatment without imaging 1, 4.
Quality improvement initiatives have successfully reduced radiograph use from 60-70% to 20-24% in pediatric emergency departments by implementing education, best practice sharing, and academic detailing, demonstrating this practice change is both feasible and sustainable 1, 4.