Manual of Clinical Anorectal Manometry

Introduction

Manometry is the diagnostic technique which measures and assesses pressure in the anal sphincter complex during the various functional stages of defecation and maintenance of faecal continence.

In strict terms, manometry simply detects the minimum and maximum pressure values in the anal canal. In clinical practice, though, the manometric examination generally encompasses additional assessments, such as anorectal sensation, which is evaluated using special electrodes, and function, usually by stimulating the evacuation of a faecal bolus using an endorectal balloon, known as the balloon expulsion test.

With specific reference to manometric evaluation exclusively aimed at determining the pressure values of the sphincter complex, conventional manometry, generally performed by means of multi- channel liquid transduction, has been shown to have numerous limitations mostly due to the broad range of normal and pathological reference values, and to the extreme differences found - as a function of age, gender, body type and BMI - when measuring the resting tone, the squeeze pressure and the pressure gradients between the rectum and the anus, even in the absence of symptoms.

In the last two decades, many attempts were made at making anorectal manometry increasingly more precise and accurate in the diagnosis of functional pelvic disorders. For this reason, modern technology introduced the use of solid transducers and software programs allowing for high-resolution 3-D reconstructions of the pressures measured in the various areas of the anal canal. In spite of the large amount of information obtained from such new approaches, including exact sphincter pressure topography, in clinical practice the gap between the huge amount of available data and their actual clinical impact and therapeutic usefulness has unfortunately become wider.

So far, therefore, almost all studies published in the literature have focused on pressure references which are unfortunately affected by multiple variables such as the instrumentation used, the calibration of the machines, the subjective component and, above all, the patients’ specific characteristics, which make each published paper isolated and almost never reproducible.

This manual does not intend to be a critical review of the literature on classical manometry or to provide sufficient details for its interpretation. Furthermore, its aim is by no means to conceal or undervalue all the pathophysiological information which classical manometry was able to collect and which represents a precious asset for anyone concerned with functional disorders of the large intestine and the pelvic floor.

Clinical Anorectal Manometry

Clinical Anorectal Manometry is directed at overcoming many, if not all, of the critical points that currently make the fundamental study of the sphincter apparatus a poorly exploited and not sufficiently valued area, notwithstanding its great potentials.

Anorectal Manometry should be:

• directly accessible to the surgeon and proctologist, and not simply interpreted by the clinician who is responsible for the patient’s therapeutic pathway;

• simple, rapid and easily repeatable , in order both to reach a diagnosis and to monitor the effects of rehabilitation or surgery;

• able to provide data for immediate and effective interpretation in order to differentiate among various pathological conditions;

• standardisable and, to the extent possible, limited by a smaller number of technical, clinical, anatomical and human variables.

In this manual we will present a new concept of manometry, based on the development of an instrument called THD® Anopress, which belongs to the first generation of portable manometers developed to study the pressures inside the anal sphincter apparatus.

From this point on, manometry using THD® Anopress, will be defined as Clinical Manometry (CAM) , i.e. a test that can or, rather, must be carried out by the Physician during the patient’s proctologic examination and which shall at no time be considered separately from the symptoms and the clinical findings that the proctologist in charge of the whole diagnostic and therapeutic pathway will evaluate.

The idea underlying Clinical Anorectal Manometry (CAM) relies on various assumptions: it is meant to be a diagnostic novelty to be shared as much as possible with the clinical proctologist, the surgeon and any healthcare professional who directly and personally manages the patient with anorectal symptoms and diseases.

Indeed, the main innovation introduced by CAM is user- friendliness and immediate detection and interpretation of the fundamental data of an anal canal pressure study.

Though classical manometry is recognised to generate multiple information on the physiology and pathophysiology of the pelvic floor, the rectum and the sphincter apparatus, it is currently limited by a number of factors such as:

• The impossibility to define normal and pathological values of clinical relevance

• the complexity of carrying