In vivo characterisation of pressure wave propagation in the rectosigmoid region as a target for neuromodulation for faecal incontinence

Participants are patients with faecal incontinence who has undergone extensive assessment through our pelvic floor clinic and has been placed on the scheduled for sacral neuromodulation. Sacral neuomodulation is the standard care for these patients. Sacral neuromodulation is routinely performed as a two-stage procedure by our colorectal surgeons. We plan to obtain our recordings during the stage I procedure (testing phase). This is typically performed under sedation but sometimes under general anaesthesia if clinically indicated. Patients are instructed to fast from midnight. Patients will undergo the standard sacral neuromodulation stage I lead placement in the morning, between 0800 and 1200 depending on operating theatre availability. This takes approximately 60-90 minutes. The high-resolution colon manometry catheter will be inserted using a flexible sigmoidoscope after the completion of sacral neuromodulation placement under the same anaesthesia. The HRCM placement typically takes round 20 minutes. Patients will be admitted overnight per usual protocol for sacral neuromodulation stage I lead placement. Manometry recordings will commence in the afternoon on the day of surgery (day 1). Patients will have to be fully alert and free from the effect of any sedative given prior to the commencement of recording. Starting at 1400, we will first perform a two-hour high-resolution colon manometry recording with no stimulation. This will be our ‘Basal Recording.’ The implanted sacral neuromodulation lead will be connected after this period of time and a further two-hour of recording starting at 1600 will be taken using the therapeutic setting, as determined by our sacral neuromodulation nurse specialist. In the normal clinical setting, this would be the setting that patients are likely to be discharged on. After the end of this two-hour recording, patients are given a standard 700kcal meal at 1800. A further two hours of recording will be performed during the time of this meal and continue post-meal. At the end of the third two-hour recording, the high-resolution colon manometry catheter will be disconnected and the sacral neuromodulator will be turned off. Patients are left undisturbed from the study investigator for the remainder of the night. Patients are instructed to not have any oral intake after midnight, except for their regular medications and water. On the following morning (day 2), patients will be woken at 0600 during nursing rounds. High-resolution colon manometry recording will commence again one hour after patients waking at 0700. The stimulator setting will be turned down to 50% of the amplitude from the previous day. Two hours of recording will be performed. At the end of the two hours, patients are given a 700kcal meal for breakfast at 0900. A further two-hour recording, will be carried out during the meal and continue after the meal. At the end of the recording, the high-resolution colon manometry catheter will be removed by applying gentle traction. Our clinical nurse specialist will set sacral neuromodulator at the therapeutic setting.The clinical team will assess patients before discharge. Post-discharge care will follow on our standard sacral neuromodulation protocol.