Functional Ultrasound and the success of Sacral NeuroModulation in Fecal Incontinence

Constantly wondering where the nearest toilet is, no longer daring to go on
group outings and no longer wearing white pants. This is daily practice for
people with fecal incontinence (FI), a total of 3-10% of the population, more
often women than men. Due to this major negative impact on quality of life, FI
is known as one of the most disabling physical complaints.

The development of FI is multifactorial, but the function of the anal sphincter
(AS), one of the pelvic floor muscles, plays the most important role. The AS
can lose its function (partly) due to disturbed control (neurological) or due
to damage to the AS, for example a total rupture during childbirth.

If primary care (pelvic physiotherapy, absorbent products and lifestyle
adjustments) and non-operative second-line care (percutaneous posterior tibial
nerve stimulation, colonic irrigation and anal tampons) do not provide
sufficient relief, sacral neuromodulation (SNM) can be used. SNM is a kind of
pacemaker for the pelvic floor muscles: An electrode wire is inserted into the
sacral spine (S3), after which local nerve stimulation (pudendal nerve)
triggers a motor response, including contraction of the pelvic floor and the
AS. However, the exact mechanism behind the working of SNM is unknown.

To determine whether the treatment with SNM is successful, patients are asked
to keep a diary about their complaints. The success of SNM is determined
subjectively based on a diary: SNM is considered successful with >=50%
improvement in complaints. This improvement is achieved in 70-80% of patients,
which means that these people have a large and lasting gain in quality of life.
However, it also means that 20-30% of patients retain their complaints and that
with "successful" SNM FI complaints may still exist, but to a lesser extent,
because 100% improvement in complaints is almost never seen. There is therefore
still room for improvement in the care of patients with FI. Better
understanding of the mechanisms behind the success and failure of SNM for FI is
essential.

The aim of this study is to describe the difference in function of the anal
sphincter, measured with functional ultrasound (4D transperineal ultrasound
[TPUS] derived strain), before and after SNM as a treatment for fecal
incontinence.

Secondary objectives:

• Describe the difference in function of the AS, measured with functional
ultrasound, between patients with and without fecal incontinence.
• Describe the relationship between function of the anal sphincter (ultrasound
strain measurements) and the patients' complaints (validated questionnaires and
diaries).
• Describe the relationship between the function of the anal sphincter based on
ultrasound strain measurements and function of the anal sphincter based on anal
myofeedback measurements.
• Describe the relationship between the function of the anal sphincter based on
TPUS strain measurements and anatomy based on endo-anal ultrasound and 4D
ultrasound.
• Describe the difference in the function of the anal sphincter (4D TPUS
strain) between patients in whom the SNM treatment for fecal incontinence is
successful (>=50% improvement in complaints) and not successful.

This prospective, observational study will analyze the feasibility of strain 4D
TPUS derived muscle strain measurements in the assessment of anal sphincter
function before and after SNM. Twenty patients will be enrolled in the study.
The cohort will follow the standard work flow for SNM with the addition of 4D
functional TPUS derived strain measurements prior to the SNM treatment (maximal
FI complaints) and after the SNM treatment (minimal FI complaints). At these
moments the in standard care executed functional measurement of
electromyography (EMG) (myofeedback [MAPLe],) will be obtained to validate the
strain measurements. Upon inclusion the demographic information is collected
and throughout the study period the clinical information that is gathered in
diaries and questionnaires will be obtained for the study (PGI-I, FIQL and
ODS).

There is a limited burden for patients to participate in this study. The first
burden is travelling, all participants need to go to the ZGT-hospital (Hengelo)
for the 4D ultrasound scan and MAPLe measurement prior to SNM test period,
after SNM test period and after final SNM placement. The second and final
burden of this research is based on filling in questionnaires on general health
and pelvic floor symptoms at the aforementioned timepoints. To lower the
burden, we aim to let the study visits take place adjacent to visits of
standard clinical care and in consultation with the patient. Moreover,
considering the large impact on the Quality of Life (QoL) of FI, we expect that
most patients are very willing to participate to this study in order to improve
the FI care.