The diagnosis of functional constipation (FC) is usually straightforward. Almost 95% of childhood constipation is functional in nature. The remaining 5% can be attributed to wide variety of conditions. Many of these etiologies are obvious by history and examination and many have other specific symptoms besides constipation. It is especially important to look for presence of any symptoms or signs that might suggest an organic etiology (red flag).
FC can usually be diagnosed with a through history and physical examination (Rome III criteria), diagnostic tests are usually not required in most children with FC. Further testing is necessary when an organic etiology is suspected children who do not seem to respond to conventional treatment should have blood tests to look for organic etiologies such as hypercalcemia, hypothyroidism and celiac disease and children suspected of having Hirschsprung disease should have an evaluation consisting of anorectal manometery, barium enema, rectal biopsy.