Topographic and manometric characterization of the recto-anal inhibitory reflex

Authors

  • G. Cheeney,

    1. Section of Neurogastroenterology, Division of Gastroenterology – Hepatology, Department of Internal Medicine, University of Iowa College of Medicine, IA, USA
    Search for more papers by this author
  • M. Nguyen,

    1. Section of Neurogastroenterology, Division of Gastroenterology – Hepatology, Department of Internal Medicine, University of Iowa College of Medicine, IA, USA
    Search for more papers by this author
  • J. Valestin,

    1. Section of Neurogastroenterology, Division of Gastroenterology – Hepatology, Department of Internal Medicine, University of Iowa College of Medicine, IA, USA
    Search for more papers by this author
  • S. S. C. Rao

    1. Section of Neurogastroenterology, Division of Gastroenterology – Hepatology, Department of Internal Medicine, University of Iowa College of Medicine, IA, USA
    Search for more papers by this author

Address for Correspondence
Satish S. C. Rao, Georgia Health Sciences University, 1120 15th Street, Augusta, GA 30912, USA.
Tel: +706 721 0211; fax: +706 721 0331;
e-mail: srao@georgiahealth.edu

Abstract

Background  Recto-anal inhibitory reflex (RAIR) is an integral part of normal defecation. The physiologic characteristics of RAIR along anal length and anterior-posterior axis are unknown. The aim of this study was to perform topographic and vector-graphic evaluation of RAIR along anal canal using high definition manometry (HDM), and examine the role of various muscle components.

Methods  Anorectal topography was assessed in 10 healthy volunteers using HDM probe with 256 sensors. Recto-anal inhibitory reflex data were analyzed every mm along the length of anal canal for topographic, baseline, residual, and plateau pressures during five mean volumes of balloon inflation (15 cc, 40 cc, 71 cc, 101 cc, 177 cc), and in 3D by dividing anal canal into 4 × 2.1 mm grids.

Key Results  Relaxation pressure progressively increases along anal canal with increasing balloon volume up to 71 cc and thereafter plateaus. In 3D, RAIR is maximally seen at the middle and upper portions of anal canal (levels 1.2–3.2 cm) and posteriorly. Peak residual pressure was seen at proximal anal canal.

Conclusions & Inferences  Recto-anal inhibitory reflex is characterized by differential anal relaxation along anterior–posterior axis, longitudinally along the length of anal canal, and it depends on the rectal distention volume. It is maximally seen at internal anal sphincter pressure zone. Multidimensional analyses indicate that external anal sphincter provides bulk of anal residual pressure. Our findings emphasize importance of sensor location and orientation; as anterior and more distal location may miss RAIR.

Ancillary