3 The procedure
3.1 Sacral nerve stimulation for idiopathic chronic non‑obstructive urinary retention involves applying an electric current to one of the sacral nerves by an electrode placed through the corresponding sacral foramen. It aims to restore the ability to empty the bladder voluntarily and to remove the need for catheterisation.
3.2 Sacral nerve stimulation involves an evaluation phase to help the patient and clinician decide if long‑term therapy will be beneficial. Evaluation also includes assessing the integrity of the sacral nerves and identifying the optimal lead location. Two main techniques are used for this evaluation, both of which are initiated by an implantation procedure done using fluoroscopic guidance, with the patient under general or local anaesthesia. The conventional technique involves percutaneously placing a temporary lead, with a unipolar electrode, alongside a sacral nerve (usually S3) and taping it to the skin surface. A newer 2‑stage technique involves implanting a permanent tined lead, with a quadripolar electrode, on the sacral nerve usually through the third sacral foramen. When the lead is correctly positioned, an extension cable is tunnelled to the proposed site for the neurostimulator, usually in the upper buttock. The lead is then tunnelled to the other buttock to provide a remote exit site through the skin.
3.3 In both techniques, the leads are attached to a small, external neurostimulator and the level of stimulation is adjusted to achieve normal voiding of urine while avoiding discomfort for the patient. The length of the evaluation phase varies but is generally around 3–7 days with the temporary lead method and approximately 2–4 weeks if a permanent lead is used.
3.4 When the evaluation phase is complete, the sacral nerve neurostimulator is implanted, usually with the patient under general anaesthesia. The neurostimulator is inserted into a subcutaneous pocket through a small incision in the upper buttock. If a permanent lead was used in the evaluation phase, it is connected to the neurostimulator. If a temporary lead was used, it is replaced by a permanent lead placed in approximately the same position and connected to the neurostimulator. The electrical current, generated by the neurostimulator and delivered by the lead, modifies sacral nerve activity. The patient can control the neurostimulator with a hand‑held programmer, increasing or decreasing the level of stimulation or turning it on and off.