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Sacral Nerve Stimulation: Choices vs
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Non-surgical Care forFecal Incontinence
WilliamAllen, AlexandraJones, HillarySimon,
andRussFarmer
Executive Summary
Sacral nerve stimulation (SNS) has revolutionized the surgical treatment of fecal
incontinence (FI). Patients that previously were treated only with medication to
minimal benet or colostomy can now get signicant symptom relief from fecal
(and urinary) incontinence with this procedure. The surgery is technically relatively
simple and has a low complication rate. However, once implanted, the need for
reoperation is high as is the cost of both entry to therapy and ongoing therapy.
Patients need to be counselled extensively and their long-term expectations managed prior to SNS implantation. While SNS is not the metaphorical “silver bullet”
for the FI, it can go a long way to improving the quality of life for a huge number of
well-selected patients.
43
PICO table
Patients
Patients with fecal
incontinence
W. Allen · A. Jones
Department of Surgery, University of Louisville, Louisville, KY, USA
e-mail: william.allen.4@louisville.edu; alexandra.jones.1@louisville.edu
H. Simon · R. Farmer (*)
Division of Colon and Rectal Surgery, Department of Surgery, University of Louisville,
Louisville, KY, USA
e-mail: hillary.simon@louisville.edu; russell.farmer@louisville.edu
© The Author(s), under exclusive license to Springer Nature
Switzerland AG 2023
K. Umanskiy, N. Hyman (eds.), Difcult Decisions in Colorectal Surgery,
Difcult Decisions in Surgery: An Evidence-Based Approach,
https://doi.org/10.1007/978-3-031-42303-1_43
Intervention Comparator
Sacral nerve
stimulation
Medical
management
Outcome
Symptom improvement,
quality of life
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W. Allen et al.
Epidemiology/Incidence ofFecal Incontinence
Fecal incontinence is increasingly more prevalent with potentially debilitating
social, economic, and health consequences. FI has been estimated to occur in up to
50% of elderly people living within care homes and up to 18% in the general population from a UK population-based survey via the 2010 National Audit of Continence
Care [1]. In the United States a large population-based survey revealed that 1in 7
people experienced fecal incontinence in their lifetime with an increased prevalence
among those with inammatory bowel disease, celiac disease, or irritable bowel
syndrome [2]. One of the most common risk factors for fecal incontinence is
increasing age. As the average life expectancy continues to increase, the incidence
of FI will continue to increase concomitantly. One study revealed FI to be the second most common cause of an individual being placed in a nursing facility [3]. This
is partly due to the increased time in care the individual requires as well as the
emotional distress experienced by the caregiver. FI has been shown to have a strong
association with both the incidence and severity of sacral decubitus ulcers [4]. FI is
associated with an overall decrease in health and increase in frailty with the inability
to adequately, and independently, complete activities of daily living. Given its correlation with deconditioning, FI has been used as a measure of functional impairment with evidence of an increased likelihood of death (hazard ratio 1.28) [5].
Diagnostic Criteria
The diagnosis of FI is made based upon a thorough history of the patient’s symptomatology. The Rome IV criteria, often modied for use in research, requires the
patient to have had recurrent, uncontrolled passage of feces for at least 3months and
the patient must have a developmental age of at least 4years [6]. A second commonly used diagnostic criteria is the Cleveland Clinic Fecal Incontinence score
(Wexner Score) which is a scoring system with a total value between 1 and 20, 0 is
complete continence and 20 is complete incontinence. The Wexner Score is calculated using the patient’s responses in regards to incontinence of gas, liquid, or solid
stool, and the necessity for lifestyle modications [7].
Causes ofFI
FI can result from a variety of etiologies including loose stool caused by infection,
diet, intestinal pathology, or functional abnormalities caused by sphincter injury,
radiation, central or peripheral neuropathy, and myopathy. Women have a higher
incidence of primary pelvic oor dysfunction compared to men, often related to
pregnancy. It has been shown that pelvic oor dysfunction was signicantly
increased in women who underwent caesarean section, spontaneous vaginal delivery, or instrumental delivery when compared with nulliparous women [8]. Obstetric
trauma remains one of the most common causes of FI due to the risk of mechanical
43 Sacral Nerve Stimulation: Choices vs Non-surgical Care forFecal Incontinence
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tears of the sphincter occurring in 0.6–9% of vaginal deliveries. The innervations of
the pelvic oor and the pudendal nerve are at risk of being damaged during prolonged or instrumented delivery.
It is projected that the number of women in the United States affected by pelvic
oor disorders will continue to increase and a similar increase will be seen in those
with FI from 10.6 million to an estimated 16.8 million by 2050 [9]. Although pelvic
oor dysfunction is more common in women, the rates of fecal incontinence in the
general population remains similar in women (8.9%) and men (7.7%) [10]. FI is a
potential complication of numerous common conditions ranging from hemorrhoidal
disease, rectal prolapse, and iatrogenic injuries from surgical procedures. Other
causes include any condition the predisposes the patient to rectal hyposensitivity
due to nerve damage, including diabetes, spinal cord injuries, and a subset of
patients with irritable bowel syndrome.
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Non-surgical Management ofFecal Incontinence
Traditionally, medical therapy and biofeedback are used in the management of FI
prior to surgery. The purpose of medical therapy focuses on increasing the solidity
of the stool and decreasing the frequency of bowel movements. Methylcellulose or
psyllium are common sources of ber which absorb liquid within the intestines and
increase the bulk of the stool, decreasing leakage of liquid feces and providing sensory feedback regarding the need to defecate. Antimotility agents such as Loperamide
act directly on the mu receptors of the longitudinal and circular muscles of the
intestines to inhibit contraction as well as peristalsis. The decrease in peristalsis acts
to increase the uptake of the liquid within the stool, increasing its bulk. Anticholinergic agents, such as hyoscyamine, are muscarinic antagonists to the smooth
muscle within the gastrointestinal tract and decrease the rate of peristalsis allowing
for similar effects seen with other antimotility agents. If the patient does not respond
to loperamide or antimuscarinics then liquid narcotics such as codeine are then used
to assist in decreasing the transit time of stool, although their systemic effects
require thorough consideration before prescribing.
Nonmedication-based treatment for FI may include pelvic oor physiotherapy
and biofeedback. Currently, the most common form of pelvic oor rehabilitation
includes electromyographic (EMG) biofeedback-guided pelvic oor muscle training (PFMT). PFMT encompasses numerous methods by which an individual
increases the coordination of the pelvic oor and anal sphincters. Patients undergo
training of the core muscles, particularly the transversus abdominis, as well as the
pelvic oor by performing Kegel contractions [11]. Biofeedback may be conducted
using a balloon placed within the rectum at the time of the PFMT to assist in
instructing the patient as well as coordinating the exercises with the sensation of
stool within the rectum. The presence of the balloon serves as the sensation of the
rectum gradually lling in order to mimic increasing stool within the rectal vault
[11]. The most common type of biofeedback uses EMG.An anal plug with surface
electrodes is placed within the rectum and the muscle contractions are recorded so
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that the patient is able to visualize the effects of performing Kegel exercises (squeezing of the pelvic oor muscles) [12]. EMG guided biofeedback therapy has been
reported to have a signicant effect on FI with up to 92% of patients in one study
experiencing improvement in symptoms [13].
W. Allen et al.
Sacral Nerve Stimulation
Sacral nerve stimulation (SNS) is a safe and efcacious way to treat fecal incontinence (FI) in patient’s refractory to behavioral and pharmacological therapies [14].
Originally described in 1982 for its role in urinary incontinence, SNS was developed by Tanegho and Schmidt [15] with ofcial FDA approval in 1997 [16]. It was
then introduced by Matzel etal. in the Lancet in 1995 for its use in FI [17]. However,
it did not gain FDA approval for this use until 2011 [18].
The underlying mechanism of action for sacral neuromodulation, or SNS,
remains unknown. Recent publications theorize results are more related to central
nervous system stimulation via afferent nervous system pathways versus previously
held beliefs that it worked via peripheral motor neurostimulation [19]. A widely
accepted theory is that SNS delivers low dose, frequent electrical pulses to the
pudendal nerve to increase both afferent and efferent effects of that central nervous
distribution resulting in reex augmentation [20].
Prior to development of SNS for use in FI, sphincteroplasty had been the mainstay of surgical treatment for fecal incontinence. A recent comparative study performed in 2017 by Rodriques etall demonstrated improvement in the Cleveland
Clinic Florida Fecal Incontinence Score (CCF-FIS) (15.9–8.4; P=0.003) compared
to sphincteroplasty (16.9–12.9; P=0.078) [21]. In 2010 another comparative study
performed by Ratto etal. [22], showed similar outcomes in incontinence scores and
QOL.Long term effects of SNS placement are still being studied. There has been
some speculation that SNS will contribute to long-term neuroplasticity via its central nervous afferent conduction. This is bolstered by the continued improvement in
the function of patients following removal of the SNS device after prolonged
implantation [1].
Placement of an SNS device is performed in a two-stage process. Patients should
initially be marked with plans for placement at the junction of the back and buttocks
with some deference of side based on patient preference, sleep and other hygiene
habits. The rst stage includes placement of temporary percutaneous leads positioned near the S3 nerve root via the S3 foramen for 1–4weeks. If the patient notes
improvement in incontinence symptoms, a more permanent neurostimulator device
is placed. A successful trial would be a reduction of incontinence symptoms by
>50%. During Stage 1, the patient is placed in prone position with exposure of buttocks and the gluteal crease. Using uoroscopic guidance, a needle is inserted into
the S3 foramen and placement is then veried using external stimulator. Correct
positioning elicits motor responses from the pelvic oor and ipsilateral great toe
plantar exion. Once positioning is veried a wire is passed through the needle and
the Seldinger technique is used to implant the temporary leads. A pocket is made,
43 Sacral Nerve Stimulation: Choices vs Non-surgical Care forFecal Incontinence
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and the leads are tunneled to the pocket which will serve as site for permeant stimulator during the next stage of implantation. The temporary external stimulator is
attached and enclosed within the pocket. If the temporary leads are successful,
Stage 2 is performed with placement of a permanent neurostimulator device. The
previous incision is opened, and electrodes exposed. The permeant stimulator,
which constitutes a combination battery pack and computer to drive delivery of
electricity, is connected and replaced back in the pocket.
Contraindications to placement however still exist. Drawbacks to using older
SNS devices include frequency of replacing the battery, inability to recharge, size
and MRI incompatibility. In certain neurogenic groups such as chronic back pain,
MS or even patients with a history of low anterior resections, the placement of an
SNS has been a relative contraindication given the high likelihood of requiring an
MRI during their lifetime. The newest generation of products from Medtronic and
Axonics have addressed this issue with the development of MRI compatible stimulators. Devices have moved from a large battery to a smaller, rechargeable battery.
Newer products such as the Interstim Micro device (2.8cm^3) is 80% smaller than
its recharge free Interstim II neurostimulator (14cm^3) [23]. In a multicenter prospective trial of 262 patients, the smaller size has also been shown to reduce amount
of subjective pain patients experience from implantation of the stimulator from 7%
with the Interstim II versus 2% in the Interstim Micro [24].
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Work Up
Initial work-up should include a Stool Diary. A Stool (Bowel) Diary may be kept for
a single week up to several weeks, and is often recorded on paper; However,
Smartphone applications have recently been developed and allow improved recording of incontinence [25]. Non-operative management has been found to benet
approximately only 25% of patients presenting with FI, highlighting the importance
of understanding operative strategies to treat FI [26]. Once baseline bowel function
has been established via a Stool Diary, surgical intervention options for FI escalate
in invasiveness and should be approached as such. The two main surgical options
for FI include SNS and anal sphincter repair.
Clinical Practice Guideline Summary
The Clinical Practice Guidelines Committee of the American Society of Colon and
Rectal Surgeons (ASCRS) have composed societal Clinical Practice Guidelines for
the treatment of FI. The guidelines are created based on the best available evidence [27].
The ASCRS strongly recommends performing thorough history, physical exam,
laboratory, and supplementary testing to rule out underlying infectious or pathologic etiologies. Anorectal physiology testing (manometry, anorectal sensation, volume tolerance, compliance), endorectal ultrasound, and pudendal nerve terminal
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motor latency can be considered to help dene the elements of dysfunction and
guide management. Validated measures that assess the nature, severity, and impact
of incontinence on quality of life should be part of the assessment for FI.The use of
a scoring index, such as the Fecal Incontinence Severity Index, St. Marks
Incontinence Score, Cleveland Clinic Florida Fecal Incontinence Score (CCF), or
other validated tool, is helpful in selecting patients for therapies and for measuring
response to treatment over time. Dietary and medical management are recommended as rst-line therapy. Biofeedback/pelvic oor physical therapy should be
considered as an adjunct to medical management of FI.Patients with more severe
symptoms, or for symptoms severely affecting quality of life, may be more appropriate for invasive therapies up to and including colostomy.
Injection of bulking agents, sphincter plication, and radiofrequency application
(Secca procedure) are less studied and poorly validated, making them a weak recommendation. Sphincter repair is highly recommended for patients with dened
external sphincter defects and can be repeated with success if necessary. Implantation
of an articial bowel sphincter remains an option for severe FI, but with low quality
evidence supporting its use. Colostomy creation is a highly recommended and supported surgical option for patients who have failed or do not wish to pursue other
therapies for FI.New and emerging technologies, such as percutaneous tibial nerve
stimulation and magnetic anal sphincter exist, however data remains insufcient to
make recommendations currently. Overall, sacral neuromodulation (SNS) should
be considered as a rst-line surgical option for incontinent patients with and without
sphincter defects. Ultimately, due to etiology variability, treatment can be challenging and should be individualized.
W. Allen et al.
SNS Candidate Selection
Prior works have compared non-operative and operative management. In a singlecenter, randomized control trial comparing groups with similar baseline characteristics, SNS implantation versus optimal medical management (pelvic oor physical
therapy, bulking agent, and dietary modication), SNS was found to signicantly
improve incontinent episodes by more than 50% in 90% of patients (50/52 patients)
[28]. The combined data of two trials showed that the number of people failing to
achieve full continence was signicantly lower when electrical stimulation was
added to biofeedback compared against biofeedback alone (RR 0.60, 95% CI 0.46
to 0.78) [29, 30]. Other prospective studies, while small, have reproduced similar
ndings, noting SNS improves FI better than conservative management31.While a
number of interventions are available for treatment of FI that vary in efcacy and
morbidity, SNS comes with validated efcacy and low morbidity. Morbidity surrounding SNS implantation includes pain or infection at the implant site pain, paresthesia, and electrode displacements or breaks requiring revision and battery
exchanges [32]
There are few contraindications and relative contraindications to SNS implantation. Bleeding diathesis, pregnancy, or other body habitus or underlying
43 Sacral Nerve Stimulation: Choices vs Non-surgical Care forFecal Incontinence
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co- morbidities which would not allow prone positioning, as well as limited cognitive function which would interfere with the operation of the SNS device, are contraindications to placement. In the past, many felt the presence of a cardiac
pacemaker was a contraindication, but there are case series that demonstrate safety
with intraoperative monitoring during placement. Relative contraindications to be
considered include psychological instability, unacceptable risk for the consequences
of infection, like patient with articial heart valves, or patients with severe or rapidly progressive neurologic disease. Frail patients, specically those who are wheelchair bound or with limited life-expectancy, would be more likely to fail SNS trial.
However, data demonstrates that patients with disorders such as multiple sclerosis,
especially in the earlier stages, have excellent functional outcomes with SNS [33]
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Difficult Decisions Surrounding SNS Implantation vs
Conservative/Medical Management
Each of the following clinical scenarios are commentaries on specic situations surrounding SNS implantation. Medical therapy is always an option to treat underlying
fecal incontinence, with the knowledge that this approach is likely to be less durable
and effective long term.
Length ofPercutaneous/Test Stimulation
Patients’ complaints of incontinence can vary signicantly based on their perceptions of their symptoms and the outcomes of these symptoms. Whereas one patient
may outline daily episodes of whole bowel incontinence with complete loss of control multiple times a day, other patients may outline fecal incontinence a few times
a week or only once a month. It is important in evaluating these patients to be
explicit in their complaints. The inclusion of these criteria has likely propagated the
adoption of the CCFFIS [7] as the standard for measuring fecal incontinence.
Symptom description and stratication via the CCFFIS or others (of which there
are many [34]) allow for appropriate determination if SNS implementation is the
appropriate approach. Many patients without fecal incontinence occurring several
times a week may indeed see a demonstrable benet with SNS implantation; however, documenting the ability of SNS to improve symptoms over a longer period
may be difcult and create nancial problems for patients in whom insurance will
not cover a demonstrated improvement in symptoms. Traditionally, most patients
undertake a one-to-two-week trial of implantation for symptoms of FI.This time
course is also prevalent throughout urologic literature [35]. However, other studies
have shown that a prolonged period of percutaneous testing with electrodes does not
lead to infection– ultimately, the risk of infection must be weighed against the benets of a prolonged testing period [36, 37]. Various studies have quoted differing
rates of infection for SNS implantation, of around 10 to 12% [38] or 13.5% [39].
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(Note: While this is consistent with published data of all kinds, this is not consistent
with the authors’ anecdotal experience).
Common skin ora produces infections most commonly, with S. aureus being
particularly prevalent [38]. One study compared the rates of colonization of removed
percutaneous lead extensions after twenty-one days of trial, resulting in a 54% rate
of S. aureus colonization deep within the wires of extension [40]. Of particular concern is the tendency for these device infections to present late in the cycle of implantation. In a large study, around 1/3 of all infections seen began presentation at least
1year following implantation [41]. An excellent review by Lee etal. provides an
overall excellent outline for perioperative steps to minimize infection and prevent
eventual explantation [35]. The methods so outlined include a signicant perioperative oral antibiotic regimen in addition to perioperative IV antibiotics to be used at
the surgeon’s discretion.
W. Allen et al.
Pertinent Clinical Questions Prior toChoosing SNS
• What is my goal length of percutaneous testing for this patient?
• Will this length of testing put my patient at high risk for infection?
• Do I need to tailor the choice of perioperative antibiotics to include oral medica-
tions to minimize risk?
• Though the risk of infection in sacral nerve stimulation is low, can my patient
successfully navigate treatment for and healing of an open posterior surgical
wound (i.e., immobility, DM, etc.?
• The risk of presacral abscess is very low [42], but would may patient toler-
ate this?
LARS: Low Anterior Resection Syndrome
SNS can be used as an adjunct to other treatments for those whose fecal incontinence proves refractory to medical management. The fall back for most surgeons
treating patients with LARS has been constipating or bulking agents in the past,
combined with enemas, pelvic oor physical therapy, and a host of other treatments
which may or may not be effective [43]. More has been written in aggregate about
SNS as a treatment for LARS than actual published data, with several meta-analyses
attempting to collate the same few patients [44–47]. Rather than utilizing LARS
scoring systems and assigning treatment modalities based on them, many CRS and
other implanting surgeons have been using SNS as a last-ditch effort to avoid a
stoma– this is especially true in many patients who often present frustrated with
their quality of life.
In essence, SNS is often the last resort for these patients before an ostomy is
made permanently. The summary of these series and others [48, 49] shows
43 Sacral Nerve Stimulation: Choices vs Non-surgical Care forFecal Incontinence
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signicant Quality of Life improvement with SNS implantation following failure of
other modalities or in combination with them. Of note when treating a patient with
LARS and using SNS, one needs to consider the nature of chemotherapeutics used
or planned, as most LARS patients have undergone surgery for cancer. If patients
are treated with chemotherapeutics that have known neurotoxic or altering effects
(i.e., platinum based chemotherapeutic agents), it is possible that SNS may be less
effective in this group. It is also important to discuss nancial implications with
these patients, as many are often at the end of their nancial ability to undergo
potentially costly surgical treatment that may be fought by their insurance as “outside” the bounds of standard medical care.
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Pertinent Clinical Questions Prior toChoosing SNS
• What symptom are you trying to improve with SNS? Be wary of patients with
signicant non- FI related LARS symptoms like tenesmus, pain, etc.
• Do the patients resources, both social and nancial, support SNS implantation in
an “edge” case?
• Are you and the patient prepared for the chance this may not work?
Mixed Constipation/Fecal Incontinence
The jury is still out on whether SNS, PTNS, and other neurogenic treatment modalities can result in signicant symptom improvement for patients with constipation.
Some studies quote improvement of constipation symptoms [50–52], while others
outline failure of this treatment [14, 53]. Clearly there is more here than simple
neural stimulation as the mixed results seen in adults do not mirror the excellent
results seen in pediatric patients with similar complaints [54]. With the seemingly
contradictory results, which patients should be getting an SNS with constipation?
There is no clear answer, however, we can impute a few workable premises.
Firstly, patients who have mixed FI and Pelvic Outlet Dysfunction related constipation following work up with manometry +/− defecography (classic or MRI) would
likely benet from SNS implantation. The classic presentation for this patient is one
who has pelvic outlet dysfunction resulting in constipation which precipitates the
consumption of laxatives or cathartics. Most patients will present having tried multiple versions of these medications in combination resulting in severe overow
incontinence of feces without sensation.
SNS implantation is less likely to be effective in patients with slow transit constipation. Some studies have shown promise [55, 56], but often results are mixed.
These patients are often better treated with more traditional modalities such as
selective colectomy or an ostomy following extensive work up. Patients with idiopathic constipation may derive some benet, but it is unknown until test stimulation.
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W. Allen et al.
Pertinent Clinical Questions Prior toChoosing SNS
• What is the underlying cause of the patients’ symptoms? Are they more appro-
priately treated with another form of surgery or medical management?
• Given that the rate of success is moderate for patients with constipation related
symptoms, can the patient afford for this not to work? (Two procedures, poten-
tially signicant charges)
Radiation Proctitis/Pelvic Radiation
SNS can be considered an adjunct to treatment for radiation proctitis that occurs
frequently following radiotherapy for any number of malignancies. Following radiation, the rectum loses capacitance and plasticity, going from an organ- similar in
function and efcacy to the stomach- to a non-dynamic tube for the conveyance of
waste. The end result often creates a situation where the rectum show moderate to
minimal functionality and continence becomes compromised [57]. The implantation of an SNS type device can potentially assist in the incontinence related to radiation proctitis, but available literature is very limited [58–60] and patients should be
counselled that results are not guaranteed / can’t be foreseen. Practitioners should
also be advised that this will likely be an “off-label” implantation and funding /
insurance may be difcult to acquire.
Pertinent Clinical Questions Prior toChoosing SNS
• Have you tried EVERYTHING else?
Congenital Sacral Malformation, Spina Bifida,
andSacral Agenesis
Implantation in patients with sacral malformations can create unique technical challenges for implanting surgeons. According to Povo etal. [61], the rate of the malformations is much higher than would be estimated in the population. In a review of
around 1000 imaging studies, they identied malformations of the sacrum at a rate
of 24.1% which could impact percutaneous placement and foraminal anatomy.
Much of the literature surrounding implantation in patients with spina bida
originates in the pediatric literature, most being small case series. Size of study notwithstanding, the results of implantation using standard percutaneous, uoroscopically guided techniques have been good, with many patients moving on to formal
implantation for either fecal incontinence, neurogenic bladder, or both [62–64]. Of
note is the 2012 study by Lansen-Koch etal. Though the number of patients was low
[10], 8 of them were able to undergo successful percutaneous implantation in the
setting of spina bida and the median age was 26.4 years old. This view is
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