Sacral Neuromodulation and Sphincteroplasty for Fecal Incontinence
Lisa C. Hickman
Cecile A. Ferrando
Perioperative Considerations
Fecal incontinence (FI) can be the result of a variety of factors, including sphincter injury, irradiation, intestinal pathology, decreased rectal compliance, central or peripheral neurologic dysfunction, diarrhea, myopathy, and functional abnormalities.
It is essential that providers screen for FI, and the clinical evaluation incorporates a comprehensive history, physical examination, and bowel function evaluation to better define the underlying etiology.
The management of FI should follow a stepwise approach, starting with conservative therapies, including diet modification, management of stool consistency, and implementing a bowel-training program.
These interventions have been found to benefit ˜25% of individuals.
For those with FI refractory to conservative management, pelvic floor physical therapy (PFPT) with biofeedback is recommended.
Interventions escalate in invasiveness thereafter and include perianal bulking agents, sacral neuromodulation (SNM), barrier devices, the Secca procedure, anal sphincter repairs, artificial sphincters, colostomies, and dynamic graciloplasties.
The two main surgical modalities utilized for FI include SNM and anal sphincter repair.
SNM was first utilized abroad for the treatment of FI starting in 1995 and was subsequently the Food and Drug Administration approved for this indication in 2011.
Patients are first asked to record a baseline diary of their FI episodes and then undergo a two-part procedure.
The first stage of the procedure involves the insertion of a tined lead into the S3 sacral foramen under fluoroscopic guidance in the operating room (OR) using sedation and local analgesia.
Once the lead is placed, it is attached to an external, temporary stimulation device.
Alternatively, patients can undergo a percutaneous nerve evaluation (PNE), which is an office placement of wire into S3 foramen without fluoroscopic guidance using local analgesia only.
Patients are then again asked to collect a diary over a 2- to 4-week period. If patients have at least a 50% improvement in FI episodes, they can go on to the second stage of the procedure, in which a permanent pulse generator is implanted in the upper buttock region and connected to the internalized lead.
If patients do not meet the threshold of improvement to proceed with the second stage, the lead is removed.
Due to the risk of a false-negative result from lead shifting after a PNE, it is highly recommended to proceed with a formal stage 1 procedure for those not meeting the improvement criteria.
Studies investigating the efficacy of SNM have shown encouraging results with up to 5-year data, demonstrating that 85% of implanted individuals maintain at least 50% improvement from their baseline FI episodes, with up to 40% of patients reporting complete continence.
Anal sphincter repairs are more invasive and are reserved for individuals with FI who have the following indications:
FI is refractory to conservative measures and PFPT with biofeedback.
There is a known sphincter defect on examination and imaging.
Perianal bulking and SNM are either not available or unsuccessful.
Individuals who meet these criteria often include postpartum women with new-onset FI and those with known sphincter injuries from nonobstetric etiologies.
SACRAL NEUROMODULATION
Perioperative Considerations
The goal of SNM is to improve the patient’s FI by at least 50%. Preoperatively, patients should be counseled on the planned technique, the need for an incontinence diary after PNE or stage 1, expected outcomes, and postoperative recovery.
Patients should be provided with chlorhexidine gluconate scrubs to utilize at home the day before and morning of surgery for cleansing of the lower back and buttock area.
Perioperative antibiotics to cover gram-positive bacteria should be administered prior to starting the stage 1 procedures. For stage 2 or a combined stage 1 and 2 procedure, during which the permanent pulse generator is implanted, coverage should be broadened to include methicillin-resistant Staphylococcus aureus, with or without gram-negative coverage. We suggest:
For a stage 1 procedure: second-generation cephalosporin
For a stage 2 or combined stages 1 and 2: vancomycin and gentamycin
Monitored anesthesia care with local anesthetic should be utilized. This type of anesthesia is beneficial as it permits the patient to provide feedback during the procedure and expedites postoperative recovery.
Patient Positioning
Patients should be placed in the prone position on an operating table that can accommodate fluoroscopy with a C-arm.
Hips should be placed at the midportion of the table where the C-arm will be located so that the sacrum can be visualized on anteroposterior (AP) films.
The patient’s feet should be just off the edge of the operating table so that motor response to sacral nerve stimulation can be appreciated.
Padding of the patient’s chest with rolled blankets or foam can help with comfort and respiration. Similarly, padding beneath the patient’s hips and shins can also provide comfort in the prone position.
The patient’s feet and low back/buttock area should remain exposed, while the shoulders, upper back, and legs can be covered.
Approach and Equipment
The patient’s buttock area should first be cleansed with soap and water if any fecal soiling is present.
The back and buttock region is prepared with a 2% chlorhexidine gluconate solution, such as ChloraPrep, starting at the low back, working more cephalad and lateral, and saving the buttocks and gluteal cleft until last. We prefer the inferior margin of the prep to reach just inferior to the tip of the coccyx. Prior to draping the patient, sufficient time should be given to permit the prep to dry.
For stage 1 procedures:
In addition to a standard drape, a sterile horizontal drape is placed over the anus that can be lifted to view the perianal (bellow’s) response without contaminating the surgical field.
A ground pad is placed on the patient’s heel and connected to the end of the test stimulation cable. The test stimulation cable adapter is also connected to the external neurostimulator (ENS). The ENS is then paired with the hand-held programmer.
FIGURE 49-1 ▪ Lateral view of sacral bone seams on fluoroscopy.
We begin using fluoroscopy and an instrument to identify the medial edges of the S2 to S4 foramina. This area is marked bilaterally using a marking pen. Lateral fluoroscopy is then used to identify the planned needle entry site, which is cephalad and parallel to the bone fusion seam of S3 (Fig. 49-1). Again, this location is marked with a marking pen.
Alternatively, if fluoroscopy is not present at the start of the procedure, the planned sites can be marked using the patient’s bony anatomy. A ruler is used to mark the point 9 cm cephalad from the tip of coccyx and 2 cm lateral on each side. An additional marking should be made 2 cm more cephalad from the previous two marks. This is also the technique utilized for a PNE in the office.
A local anesthetic, such as 0.25% bupivacaine, is then injected to create a wheal subdermally at the planned entry site.
The foramen needle is inserted in a cephalocaudal direction to a depth at or below the posterior sacral surface near the hillock. Fluoroscopy is used to confirm proper placement.
The sterile end of the test stimulation cable is then connected to the noninsulated area on the foramen needle, and the programing device is activated to confirm appropriate S3 motor and sensory responses at low-amplitude levels:
The motor responses include plantar flexion of the great toe and a bellow’s response, which is a tightening or pulling in motion best seen in the perianal region.
The sensory response in women is stimulation in the vaginal and perineal region and in men is stimulation at the base of the penis, scrotum, and rectum.
The stylet from the foramen needle is removed, and the directional guide is inserted through the foramen needle, after which the foramen needle is removed. Care must be taken to ensure that the directional guide is stabilized so that it is not accidentally removed or displaced.
An #11 blade scalpel is used to make a small incision at the base of the directional guide.
The lead introducer sheath and dilator is placed over the directional guide. Fluoroscopy in the lateral view should be used to ensure that the radiopaque marker is located at approximately half the depth of the sacrum.
The guidewire and dilator are removed, leaving the introducer sheath in place. The tinned lead is then inserted, and fluoroscopy is utilized to achieve lead placement just inferior to the posterior surface of the sacrum on the lateral view (Fig. 49-2). On the AP view, the lead tip should point laterally and slightly caudally (Fig. 49-3).
Each of the four electrodes are again tested for appropriate motor and sensory responses with the test stimulation cable.
Under fluoroscopy, the introducer sheath is carefully removed while concurrently stabilizing the lead in place, which deploys the lead tines.
FIGURE 49-2 ▪ Lateral view of tined lead placement in relation to sacrum.
FIGURE 49-3 ▪ Anteroposterior view of tined lead placement in relation to sacral foramen.
The stylet is removed from the lead and again tested for appropriate motor and sensory responses.
Next, the connection site, which is generally located below the iliac crest and lateral to the sacrum, is identified and marked.
The area is injected with local anesthetic, and a horizontal incision ˜4-5 cm in length is made.
Blunt dissection is then used to create a pocket that will be the site for the future permanent pulse generator. This pocket can be irrigated with a dilute antibiotic solution, such as bacitracin, in sterile water.
The tunneling tool with passing straw is inserted at the lead exit site and passed underneath the skin in the subcutaneous tissue to exit the newly created pocket. The tunneling tool is then removed, leaving the straw in place, through which the lead is passed to exit the pocket. The straw is then removed.Related posts:
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