Constipation in Children Diagnostics

Laboratory Tests and Ancillaries

It is generally not necessary to have laboratory studies unless an organic disease is suspected from history and PE and the child is unresponsive to adequate treatment. Fecal occult blood tests may be done in infants and children with constipation who have diarrhea, abdominal pain, failure to thrive, or history of colorectal cancer or polyps. Organic, metabolic, and endocrine diseases can be confirmed by performing thyroid-stimulating hormone (TSH), calcium and lead levels, celiac disease antibodies, and a sweat test.  

Anorectal Manometry (ARM)  

Anorectal manometry directly measures the sensorimotor function (eg resting pressure, inhibitory reflex, squeeze pressure) of the anus and rectum. It is indicated for patients suspected of Hirschsprung disease, rectal outlet obstruction, and patients with history of surgery for Hirschsprung disease or imperforate anus.  

Colonic Manometry  

Colonic manometry measures intraluminal pressure throughout the length of the colon to identify motility deficits and dysfunction using a catheter inserted endoscopically or via fluoroscopic guidance. It may be used for children with intractable constipation considering surgical interventions.  

Rectal Biopsy  

In rectal biopsy, a small sample of a full-thickness biopsy is taken 3 cm above the anal verge. It is the definitive means of diagnosing Hirschsprung disease. The presence of hypertrophied nerves on microscopy establishes the diagnosis of Hirschsprung disease. It is not indicated when clinical and imaging findings are suggestive of functional constipation.

Imaging

Abdominal Radiography  

Abdominal radiography may be used for assessing fecal impaction in children with inconclusive medical history and PE. It shows the amount of stool present. It is useful in obese children and those who cannot have a DRE done. However, it has a limited value in clinically assessing constipation due to poor correlation between radiological and clinical diagnosis.  

Barium Enema  

In barium enema, a contrast dye (barium) coats the lining of the bowel for clear visualization on an X-ray. It is useful in diagnosing Hirschsprung’s disease by demonstrating the transition zone (change in the diameter of the colon from the narrow aganglionic segment to a dilated ganglionic segment). It also helps evaluate motility of the colon (slow motility in megasigmoid and impacted stool). However, it is less reliable during the first months of life due to insufficient dilation of the proximal colon for the transition zone to be demonstrable.  

Constipation in Children_Diagnostics