Anorectal manometry in dyssynergic defecation: Are we there yet?

Dyssynergic defecation (DD) refers to the paradoxical contraction or inadequate relaxation of the pelvic floor on attempted defecation. As symptoms do not reliably discriminate between subtypes of chronic constipation, diagnostic tests are frequently required. The Rome III criteria require a combination of functional constipation and two abnormal dynamic tests of the pelvic floor on attempted defecation (i.e., impaired evacuation on balloon expulsion or defecography; inappropriate contraction of the pelvic floor muscles or incomplete relaxation of the anal sphincter on manometry, electromyography, or imaging; inadequate propulsive forces assessed by manometry or imaging) to diagnose functional defecation disorder. Dyssynergic defecation is seen in a subset of patients with functional defecation disorder, and is defined as inappropriate contraction of the pelvic floor or less than 20% relaxation of basal resting sphincter pressure with adequate propulsive forces during attempted defecation. Among the various available tests, anorectal manometry (ARM) and balloon expulsion test (BET) are the most commonly performed tests for diagnosis of DD. In fact, a combination of ARM and BET has been recommended as the initial test of choice to assess patients with defecatory disorders; some authors advocate defecography (either barium or MR) if resources allow. Anorectal manometry (ARM) is routinely performed for objective assessment of anal sphincter function and anorectal coordination. Prior to the introduction of high-resolution manometry catheters, anorectal manometry was performed with non-high resolution, waterperfused or solid state catheters. High resolution manometry with solid state catheters has set new benchmarks in research of assessment of gastrointestinal motility. This is partly due to the fidelity and reproducibility of the results obtained on solid state systems as compared to systems. The water-perfused systems are still popular in clinical practice due to their low cost as well as adequacy in providing accurate diagnosis for patient management. Despite increasing use of solid state systems for anorectal function research, they are yet to gain as much acceptance as that for esophageal function. In fact, ARM HRM with water-perfused catheter and solid state catheter show comparable results for most parameters, except that anal sphincter pressures recorded by solid state catheters tend to be higher. The latest improvisation in solid state technology has been threedimensional high-definition probe (3D HDAM). which has 256 sensors. 3-D HDAM is useful for assessing the anal canal morphology as well as detailed pressure measurements. Balloon expulsion test is a good test to assess simulated evacuation; a balloon-tipped catheter is inserted into the rectum, and filled with water or air (typically 50 mL). The time required for the patient to evacuate the balloon in privacy is measured. However, the methods of conducting the test vary across studies. In some centers, balloon BET is conducted in the left lateral decubitus position, wherein a rectal balloon is connected over a pulley; weights are added to provide external traction when necessary to facilitate expulsion of rectal balloon.The left lateral position is unphysiological for defecation. Almost 36% of normal healthy subjects