The Role of Impedance Planimetry in Anorectal Assessment

Excerpt

To the Editor—The authors are to be commended for their novel usage of impedance planimetry as an index of “static” rectal motility and activity.1 However, the advantage of the impedance planimetric technique is to more readily define reproducible values for dynamic rectal compliance and elasticity, where conventional proctometrographic (pressure/volume) curves have proven less accurate. The real-time ultrasonographic measurement of rectal cross-sectional areas (CSA) during distension (and deflation) is less reliant on the intrinsic compliance characteristics of the balloon assembly or on inherent rectal geometry.2 In this sense, impedance planimetry provides a better reflection of rectal wall stiffness and altered viscoelastic properties during inflation/deflation cycles.3 Given this, it is unlikely that “resting” planimetric determinations provide any more information over ambulatory manometry to describe preprandial or postprandial anorectal pressure wave patterns in health or disease. Their study would be of greater interest if comparisons were made by using the technology statically, particularly in patients with obstructed defecation and fecal incontinence. In the former setting, low-amplitude wave activity might show anorectal gradient reversal, which could correlate with disturbances in dynamic levator contraction during provocative maneuvers, as has been recently shown with dynamic CT imaging.4 It also might provide some recognizable wave patterns, which could signal a more objective diagnosis of anismus.5 In incontinence, an aberrant anorectal sampling mechanism (as suggested by the authors), in which the patient is unaware of rectal activity, may provide for a more subtle diagnosis particularly when isometric (i.e., CSA-stable) contractions and relaxations might correlate with episodes of reported leakage. It also is possible that subtle patterns of anorectal dysrhythmia may be indicative of milder grades of obstructed defecation and incontinence, particularly when there is doubt regarding the severity of the complaint reported by the patient. …