Keywords

1 Introduction

The physiological mechanisms behind normal anorectal function result from a perfect interaction among the anal sphincter complex, the rectal reservoir, and fecal consistency. Anal incontinence (AI) is defined as the involuntary passage of rectal contents (feces and/or gas) through the anal canal and the inability to defer evacuation to socially convenient times [1]. The main cause of AI is considered to be sphincter lesions, but frequently the dysfunction occurs also in subjects with intact sphincters. In some of those cases, neuropathy plays the major role by causing sensory-motor alterations [2, 3]. Symptom severity encompasses a wide clinical spectrum, from mild to severe, and can be specifically graded by several clinical scores commonly used to study patients [4, 5]. Soiling, seepage and incontinence to gas are commonly defined as “minor incontinence” whereas incontinence to liquid and solid stools is defined as “major incontinence”. Different classifications of AI divide its clinical presentation into two entities based on whether the patient is able to feel the defecation stimulus but is unable to hold it (urge incontinence) or not (passive incontinence). Although not as a rule, passive AI commonly results from internal anal sphincter (IAS) lesions [6], whereas a structurally compromised external anal sphincter (EAS) is typically associated with urge AI.

Pelvic floor rehabilitation is commonly advocated as the first-line therapy when the global clinical-physiatric evaluation of the patient indicates it [7]; if the clinical outcomes are not satisfactory, the use of intersphincteric injectable bulking agents has been suggested about two decades ago as a possible treatment option [8] providing a feasible and minimally invasive technique hopefully granting a higher clinical response than other more “aggressive” procedures. Among the different bulking agents, Gatekeeper (GK) self-expandable solid prostheses have shown promising short- and middle-term results [9, 10]. Previously, different types of bulking agent had been used [11,12,13,14], but only a short-term benefit from the injections was reported, regardless of the material used. The major problem with the previously used anal bulking agents was their reduced efficacy with time, probably due to a variable combination of degradation and/or diffusion through the tissue adjacent to the injection site or, sometimes, far from that site. The data presented by Ratto et al. in 2011 [8] suggested that the implantation of the GK device was able to overcome all of these potential problems.

2 Indications and Contraindications

The GK device currently used consists of a delivery instrument and solid prostheses (n = 4 in the first description, subsequently n = 6) made of inert hyexpan (polyacrylonitrile) that, once implanted, characteristically expands up to 700% of its former volume by slow water absorption within 48 h from implantation. The prostheses are compliant to external pressures without losing their original shape. For these reasons the implants are usually placed in the intersphincteric space, in the belief that this will achieve a more effective distribution of the bulking effect and minimize the potential risk of erosion, ulceration, fistulation of the anal canal and possible prosthesis displacement [8]. However, implantation methods, as well the volume and number of prostheses vary between studies [15]. Launched as the evolution of GK, Sphinkeeper (SK) features more and longer hyexpan prostheses [8, 9]. These are long enough (23 mm in final length) to reconstitute the normal anal canal length and wide enough (7 mm in final diameter) to ensure a significant filling ability, so SK allows treatment of more sizeable defects in the IAS or EAS.

Implantation of these devices is indicated in patients whose onset of AI is ≥6 months before the first visit and symptoms are refractory to all standard conservative measures (pharmacologic, behavioral, and pelvic floor rehabilitation). Before implantation, at baseline, patients are evaluated on the basis of a detailed medical history and physical examination; when indicated, a colonoscopy can be performed. Particular attention has to be paid to investigate previous surgery, trauma and/or local radiotherapy, congenital anorectal malformations, comorbidity, AI symptoms, characteristics and diary, ability to defer defecation, and need to wear pads and/or take constipating drugs. Health status and quality of life (QoL) are evaluated at baseline and then after implantation [16, 17]. Anorectal manometry and endoanal ultrasound (EAUS) should be performed to assess anorectal function and morphology and to identify and quantify any lesion of the anal sphincter complex, determine anal canal length and muscle tension as well as resting tone.

GK/SK are not indicated in the presence of: IAS lesion >60° and/or EAS lesion >90° identified on ultrasound; active perianal sepsis; severe anal scarring; bowel disease with anorectal involvement; active treatments for anal or rectal cancer. The presence of diabetes mellitus, pudendal neuropathy, and previous implantation of sacral nerve stimulator do not represent contraindications for the GK procedure, although accurate preoperative evaluation of coexisting clinical conditions that may negatively impact outcomes is encouraged.

3 Surgical Technique

After spinal/local anesthesia [18], with the patient in the lithotomy position, small (2 mm) skin incisions are performed at 12, 3, 6, and 9 o’clock or at 1, 3, 5, 7, 9, and 11 o’clock in the intersphincteric groove to allow implantation of four or six prostheses by using a specifically designed delivery system, which is functionally similar whether GK or SK prostheses are being implanted; in the latter case, up to ten small skin incisions can be used. Under digital guidance, the introducer is inserted into the intersphincteric space through a short subcutaneous tunnel and pushed up to reach the upper part of the anal canal. The introducer is placed in the upper third of the anal canal, at the level of the puborectalis muscle. Once in place, the gun is fired resulting in retraction of the cannula and deployment of the prosthesis. When the proximal part of the prosthesis reaches the tip of the cannula, the whole cannula retracts completely inside the delivery system and the prosthesis is released in place in the desired position within the intersphincteric space. The delivery device is then withdrawn. The implants are distributed equally around the anal canal, as it is believed that the actual position does not influence the outcome, even in the presence of EAS or IAS tears. The prostheses are placed in the same position in all patients, irrespective of the location of possible EAS/IAS lesions. Beginning from the very first reports of GK implantation, the prostheses were placed at 3, 6, 9 and 12 o’clock positions for convenience but it is likely that, provided the implants are inserted correctly and distributed equally around the anal canal, the actual position does not influence the outcome. As for the number of prostheses implanted, it has been recently demonstrated that the greater the number of the prostheses, the better the clinical outcome [19]. Some authors [8] perform skin incisions about 2 cm away from the anal verge to minimize the risk of wound contamination during bowel movements. Nonlinear tunneling through the soft subcutaneous tissues to reach the intersphincteric plane from the skin incision is thought to avoid possible prosthesis extrusion along the track. In our procedure [18], all of the steps are verified by palpation and direct vision using the Eisenhammer anal speculum. However, prosthesis placement can also be performed under EAUS guidance to monitor the procedure step by step and ensure correct positioning of the prostheses, but this is not mandatory and simple digital palpations by an expert physician can be enough to guarantee proper positioning of the prostheses. When performed, EAUS is used to confirm the position of the prosthesis, which appears as a hyperechoic dot with a hypoechoic shadow behind it. Three-dimensional EAUS (3D-EAUS) was used by some groups and showed a continuous hyperechoic line after implantation [9]. Finally, the skin wounds are sutured with resorbable material. Patients are usually discharged on the same day and instructed to avoid any trauma or sexual practice during the first 48 h after implantation. Bed rest is usually recommended and aims at decreasing the risk of early prosthesis dislocation. A 5-day course of antibiotics is also prescribed. Patients are assessed at follow-up and 3D-EAUS is performed to check the location of the prostheses.

4 Implantation Results

Implantation of GK/SK results in a significant improvement in episodes of major AI and on all the scores used to stratify AI severity preoperatively (Cleveland Clinic Fecal Incontinence Score [CCFIS], Vaizey score). The ability to postpone defecation for longer and postevacuation soiling are both significantly improved in the majority of patients undergoing GK/SK implantation. Of note is the improvement of QoL scores (FIQL, SF-36), suggesting regained health and comfort in patients treated with GK. The postimplantation anatomical changes in the sphincter complex—confirmed by ultrasound (Fig. 14.1)—are thought to play a major role in the functional improvements. Indeed, it has been fully demonstrated that increasing the in vivo length of the EAS complex increases its contraction [20, 21]; an overall increase in muscle tension of the anal sphincter complex has been observed and recently demonstrated after GK implantation. Such a positive change may be crucial in altering the pathophysiological mechanisms which are believed to be associated with the development of AI symptoms. Our results [18] show good initial improvements in CCFIS that were sustained up to 36 months after implantation. We also provided data regarding sphincter morphology and function by 3D-EAUS and high-resolution anal manometry (HRAM). Our rate of prosthesis displacement was lower (20%) and fully asymptomatic compared with another study (52%) [22]. Furthermore, in our experience, the GK procedure was not intraoperatively assisted by EAUS, confirming that prosthetic delivery into the intersphincteric space can be adequately accomplished after a short learning curve (minimum of five proctored cases). HRAM showed an overall increase in functional anal canal length, anal resting pressure, and maximum squeeze. Improvements in QoL following GK implantation have also been described elsewhere [10, 19].

Fig. 14.1
Three ultrasound images of anatomical structures after the implantation of gatekeepers. The images contain a dark circle at the center covered by muscles all around. In the last image, a series of curved lines are detected in the muscle layer.

Gatekeeper implantation in patients with anal incontinence: ultrasonographic evidence of prostheses located in the intersphincteric space, surrounding the anal canal

Full size image

Few studies have compared GK and SK implantation results, and even fewer studies have investigated SK results beyond 1 year. Indeed, clinical improvements are observed at 1 year after implantation, regardless of the bulking agent system used. Apparently [19], SK confers the same benefits as GK in terms of morphofunctional remodeling of the sphincter complex and the increase in muscle tension is higher after implantation of a greater number of prostheses. The postimplantation increase in muscle tone (after controlling for baseline values) is significantly higher in patients undergoing SK than GK implantation, resulting in a better improvement in CCFIS at 12 months. In patients with loose, patulous, funnel-like or keyhole-shaped anal canal, SK could offer the opportunity to reconstitute the cylindrical shape of the anal canal, while in patients with sphincteric lesions it could reinforce the area of scarring and improve the contribution to continence of the remaining intact sphincters. Finally, SK could have a non-negligible role as adjunctive therapy in patients with incomplete resolution of symptoms after other procedures for AI. In conclusion, implantation of SK is as feasible as that of GK in patients with different types of AI, it does not give rise to major complications or dislodgement, and it enhances effectiveness due to the greater number and dimensions of the prostheses.

5 Adverse Effects: Displacement

Studies have been conducted searching for intra- and postoperative complications, in particular looking at clinical and/or EAUS evidence of bleeding at/from the sites of implantation, anorectal sepsis (anorectal abscess and/or fistula), signs of local and systemic inflammation, pain, duration of analgesic therapy and urinary retention [9]. Implantation is not followed by septic or adverse reactions, does not result in short-term dislodgement and is well tolerated. No acute sepsis at the site of implantation and around the prostheses was documented within a 90-day period. No long-lasting symptoms (including anorectal pain and discomfort) directly or indirectly related to the implanted prostheses have been recorded. This was confirmed in a large population that underwent GK implantation [9, 10] or in patients treated with SK implantation. Compared to other treatment options for fecal incontinence, in fact, these procedures boast a number of potential advantages including the minimally invasive approach (that may mitigate risk in frail patients) and repeatability (i.e., replacement after removal of protruding prosthesis).

GK/SK implantation is very safe. Acute sepsis at the site of implantation and around the prostheses is rarely recorded. The only adverse event of concern reported to date is prosthetic displacement. This was first described in a case report in 2014, in which EAUS demonstrated the migration of GK implants in a patient reporting no improvement in AI symptoms, as well as perianal pain and swelling [23]. This complication was then studied further and is now assessed with rates ranging between 6% and 49% [22].