Tests
1st tests to order
no initial test
Test
Characteristic history and examination findings are often sufficient to diagnose the condition.
Result
clinical diagnosis
Tests to consider
abdominal radiograph
Test
Do not routinely obtain abdominal radiographs for suspected constipation.[13][32][33][34] However, abdominal radiographs may be considered in patients with red flag signs or symptoms suggesting an organic cause for the constipation (e.g., abdominal distension, abnormal findings on neurologic exam, intermittent diarrhea and explosive stools, occult blood in stool) or as part of specialist ongoing management of intractable idiopathic constipation.[13][32]
It may also be useful if a rectal exam is required (e.g., suspected fecal impaction) but not desirable (e.g., in a child with a history of trauma) or for monitoring purposes posttreatment.[13][33]
Result
significant stool burden may support a diagnosis of constipation
radiopaque marker colonic transit study
Test
Abdominal radiograph done after ingestion of radiopaque gut transit marker. Used to measure movement of stool through the colon and assess for abnormalities of transit. Transit studies are not recommended for routine diagnosis of idiopathic constipation in children.[13][32][33] Consider as part of specialist ongoing management of intractable idiopathic constipation.[32] May also be considered to discriminate between functional constipation and functional nonretentive fecal incontinence and in situations in which the diagnosis is not clear.[33]
Result
slow colonic transit, as measured by delay in marker movement throughout the colon, confirms slow transit variety of constipation
abdominal ultrasound
Test
This is a useful investigation for softened stools, which avoids x-ray exposure, and can be used to exclude bladder anomalies or, rarely, solid tumors obstructing the pelvic outlet (e.g., neuroblastoma). Do not routinely perform abdominal ultrasound for suspected functional constipation.[32][33]
Result
rectal mass and its effect on the bladder observed
contrast enema
rectal suction biopsy
Test
More commonly needed if onset of constipation occurred together with delayed passage of meconium, abdominal distention, and explosive stool upon digital rectal exam. However, may also be warranted if patient has longstanding history of constipation, especially if anorectal manometry does not prove normal rectoanal inhibitory reflex.
Excludes possibility of Hirschsprung disease.
Result
presence of ganglion cells and absence of hypertrophic nerve fiber bundles
psychological assessment
Test
This may explain why symptoms are intractable in the absence of a severe physiologic predisposition. Sometimes, constipation may be an early sign of autism or ADHD.
Result
evidence of autism spectrum disorder, ADHD, oppositional disorder, or developmental delay
Emerging tests
anorectal manometry
Test
Helpful in assessing normal reflexes to evaluate for Hirschsprung disease. If performed without anesthesia, provides a measure of rectal sensation and pelvic floor movement, thus enabling biofeedback for appropriate older children with abnormal coordination.
Result
pattern of rectoanal inhibitory reflex may be exaggerated with neuropathic causes or absent in Hirschsprung disease
colonic manometry
Test
Useful in evaluating colonic contractions. Performed most often on patients with constipation refractory to medications. Can be helpful in identifying patients who may benefit from surgical intervention.
Result
lack of high amplitude propagating contractions suggests decreased colonic contractions which may indicate further intervention
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