Usefulness of diagnostic tests in constipation

The evaluation of constipation should be approached in a selective and stepwise manner, with the aim of identifying the underlying pathophysiological mechanism responsible for symptoms and guiding therapeutic decision-making, rather than merely “confirming” a diagnosis. Complementary diagnostic tests are primarily indicated in refractory constipation, following the failure of appropriate initial management, and only when their results are likely to modify clinical management. A substantial proportion of patients present with defecatory disorders, which are frequently underrecognized and may coexist with or contribute to slow colonic transit. In this context, anorectal functional evaluation, including anorectal manometry and the balloon expulsion test, represents the first diagnostic step, as it allows the identification of patients who are candidates for anorectal biofeedback, the treatment of choice in these cases. Colonic transit studies should be reserved as second-line investigations, particularly when symptoms persist after exclusion or treatment of a defecatory disorder, or prior to considering advanced therapeutic interventions, such as surgery. Defecography plays a complementary and selective role, proving useful when dynamic anatomical abnormalities are suspected or when functional test results are inconclusive. Overall, it is emphasized that the value of diagnostic testing lies in its appropriate indication and clinical integration, thereby avoiding unnecessary investigations and inappropriate treatments.