Current Techniques of Assessing Defecation Dynamics

The pathophysiology of defecation disorders is multifactorial. An ideal test should identify the underlying cause(s) and provide guidelines for treatment. Unfortunately, there is no such single test. But several techniques are available that could provide comprehensive information regarding the changes in defecation dynamics. Among these, anorectal manometry offers the most useful test for clinicians. Manometry may provide objective evidence for impaired rectal sensation, poor rectoanal coordination, weak anal sphincters or changes that support a diagnosis of obstructive defecation. Other tests such as the balloon expulsion test may serve as screening tools for patients with constipation. In a patient with fecal incontinence, anal endosonography may localize the sphincter defect and aid surgical reconstruction. The pudendal nerve latency test may provide a pathophysiological basis for a weak anal sphincter. Imaging techniques such as defecography may provide useful information regarding rectal prolapse or levator ani dysfunction. Ideally, the clinician should utilize these tests either to confirm a clinical suspicion or to provide new information that could aid management. This review provides an update regarding the various tests that are available for assessing defecation and provides some practical guidelines for performing manometry.