Investigations
1st investigations to order
no initial test
Test
Characteristic history and examination findings are often sufficient to diagnose the condition.
Result
clinical diagnosis
Investigations to consider
abdominal x-ray
Test
Not routinely required, especially if stools are easily palpated in the abdomen. However, may be useful to assess the amount of stool when stools are softened by medication, symptoms persist, and the degree of residual retention is uncertain.
May also be useful if a rectal examination is required but not desirable (e.g., in a child with a history of trauma) or for monitoring purposes post-treatment.[15]
Result
significant stool burden may support a diagnosis of constipation
radiopaque marker colonic transit study
Test
Abdominal x-ray done after ingestion of radiopaque gut transit marker. Used to measure movement of stool through the colon and assess for abnormalities of transit.
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 tumours obstructing the pelvic outlet (e.g., neuroblastoma).
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 distension, and explosive stool upon digital rectal examination. 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's disease.
Result
presence of ganglion cells and absence of hypertrophic nerve fibre bundles
psychological assessment
Test
This may explain why symptoms are intractable in the absence of a severe physiological 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's disease. If performed without anaesthesia, provides a measure of rectal sensation and pelvic floor movement, thus enabling biofeedback for appropriate older children with abnormal co-ordination.
Result
pattern of recto-anal inhibitory reflex may be exaggerated with neuropathic causes or absent in Hirschsprung's 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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