Assessment of Anatomic, Physiologic and Biomechanical Characteristics of the Anal Canal and Pelvic Floor. An Observational Pilot Study

Background

Fecal incontinence (FI) is affecting self-confidence and can lead to social isolation and even loss of employment Often conservative treatment as the first option is ineffective and surgical interventions follow conservative are necessary.

Small defects of the anal sphincter muscles might be treated with sphincter repair and sacral neuromodulation (SNM) However, patients rarely become fully continent or short-term results deteriorate in the long term [1]. Those patients and patients with large defects are candidates for a neosphincter procedure (artificial bowel sphincter or graciloplasty). However, the success rate of these methods is limited and the explantation rate is high. A permanent colostomy associated with massive psychosocial impairment remains as ultimate treatment option With the project Smart Muscle for Incontinence Treatment (SMIT) a multidisciplinary consortium consisting of representatives ranging from clinical medicine via microelectronics towards biomaterial science aims to develop a novel implant to treat faecal incontinence. The aim of this campaign includes development of implantable prototype devices acting as artificial continence muscles using low-voltage electrically activated polymers (EAPs) controlled by implemented pressure sensors and the patient.

Subsequently, the knowledge of the anatomical and biomechanical properties of the anal sphincter complex are of cardinal importance. Most of the existing data on anatomy and physiology results is based on old studies and almost no data on biomechanical properties are available. However, new technologies or even merging data from different examination methods might provide new information in this field.

Accurate imaging data on the pelvic floor region is crucial for the development of a new, implantable device for restoration of fecal continence. Optimal size (inner, outer diameter, length) and geometrical shape (cylinder, cone, torus) adapted to different functional states (rest, squeezing, defecation) will improve function and prevent erosion and consequent infection of such a prosthesis.

With this study, the investigators aim to correlate three-dimensional endoanal ultrasonographic images with MRI images. The combination of different imaging techniques has been demonstrated to eliminate individual drawbacks of the examination methods and therefore would allow a precise description of the tissue [2]. The registered data with their complementary information would permit the distinct segmentation and three-dimensional presentations of the anatomical structures in the pelvic area. This information has a great potential to facilitate diagnostics and surgical planning in this region.

High-resolution anal manometry (HRAM) provides intra-anal pressure during rest or maximum pressure with high spatial and time resolution.

However Biomechanical properties of the anal canal as elasticity or stiffness (compliance or flexibility) of the tissue representing important parameters for a continence organ are not routinely evaluated in daily clinical practice. Functional Lumen Imaging Probe (FLIP) allows the measurement of a cross sectional area (CSA) with respect to applied luminal pressure, respectively. FLIP has the potential to be useful in order to assess the biomechanical properties of the sphincter region. Such information potentially gives new insights in physiology and pathophysiology of the continence process.

With this pilot study, the investigators aim to acquire anatomical and biomechanical data using established (manometry) and novel technologies (merging endoanal ultrasound and MRI data) in 20 healthy probands (10 male, 10 female).

Objective

Primary objective is to collect anatomical, physiological and biomechanical characteristics of the continence organ (sphincters and pelvic floor) in order to specify properties of a new implant for the treatment of faecal incontinence.

Secondary objectives are: test feasibility of FLIP in measuring the biomechanical properties of the anal canal and test feasibility of merging 3D US data and MR images.

Further this preliminary data will be used to plan an observational study comparing healthy probands and patients with incontinence.

Methods

For the assessment of the morphology ultra sound and MRI will be used, whereas FLIP (functional luminance imaging probe) and HRAM (high resolution anal manometry) are the modality of choice to investigate the biomechanical properties of the sphincter complex.