This document discusses the classification, identification, risk factors, prevention, and repair of obstetric anal sphincter injuries (OASIS). It begins by classifying first through fourth degree perineal tears, noting that third degree tears involve the anal sphincter complex. The incidence of OASIS is increasing due to improved detection. Risk factors include high birthweight, forceps delivery, and prolonged second stage of labor. Prevention methods discussed include mediolateral episiotomy, perineal protection techniques, warm compresses, and perineal massage. Proper identification of OASIS requires visual and digital rectal examination. Repair involves closing the anorectal mucosa, internal anal sphincter

1. 1 Dr Muhamed Al Bellehy MD
Dr Muhamed Al Bellehy MD
Perineal Laceration and obstetric anal sphincter injuries Repairs
Sources
1. Green-top Guideline No. 29 June 2015The Management of Third- and Fourth-Degree Perineal
Tears (obstetric anal sphincter injuries, referred to as OASIS)
2. William’s 25th
edition
Classification by Sultan, 1999
INJURY TO OASIS_ includes
3rd- & 4th-
degree tears.
IAS has role in
continence
First-degree tear  perineal skin and/or vaginal mucosa.
Second-degree  Injury to perineum involving perineal muscles but not anal sphincter.
Third-degree INVOLVING ANAL
SPHINCTER
COMPLEX
 Grade 3a tear: < 50% of external anal sphincter (EAS) thickness torn
 Grade 3b tear: > 50% of EAS thickness torn.
 Grade 3c tear: Both EAS & internal anal sphincter (IAS) torn.
Fourth-degree  involving anal sphincter complex (EAS & IAS) & ANORECTAL MUCOSA.
If there is any doubt about degree of 3rd-degree tear, classify it to the higher degree rather than the lower degree
identification of IAS may be difficult in acute obstetric trauma, but every attempt should be made to exclude & document
injury to IAS
 Rectal buttonhole tear
o tear that involves rectal mucosa with an intact anal sphincter complex (not 4th-degree tear)
o If not recognised and repaired, this type of tear may lead to a rectovaginal fistula

2. 2 Dr Muhamed Al Bellehy MD
Dr Muhamed Al Bellehy MD
Postpartum rectal buttonhole tear

3. 3 Dr Muhamed Al Bellehy MD
Dr Muhamed Al Bellehy MD
Background
 Incidence of OASIS
o in singleton term cephalic vaginal first births in England_ tripled from 1.8% to 5.9% from 2000 to 2012.
o overall incidence in the UK is 2.9% (range 0–8%), 6.1% in primiparae _ 1.7% in multiparae.
 With increased training, increase in the detection of anal sphincter injuries.
 an increasing incidence of 3rd- or 4th-degree perineal tears does not necessarily indicate poor quality care.
It may indicate, at least in the short term, an improved quality of care through better detection & reporting.
 ‘anorectal mucosa’  The lining of anal canal varies along its length due to its embryological derivation.
o proximal anal canal is lined with rectal mucosa (columnar epithelium)
o distal 1–1.5 cm is lined with modified squamous epithelium.
 Anal incontinence: the complaint of involuntary loss of flatus and/or faeces affecting QOL.
 incontinence related to IAS injury vs related to EAS injury alone
o In a prospective study after OASIS, tear (EAS)compared with tear (IAS)
 significantly poorer outcome with respect to
 development of defaecatory symptoms
 anal manometry results
 associated quality of life.
 anal incontinence.
o IAS -defect thickness (partial thickness defect > one quadrant or full thickness IAS defect) was
predictive of severe incontinence
Prediction
 risk factors do not allow the accurate prediction of OASIS.
risk factors Risk factors for sustaining recurrent OASIS in the subsequent
pregnancy include (limited evidence)
Asian ethnicity (OR 2.27) Asian ethnicity
Nulliparity (relative risk [RR] 6.97)
birthweight > 4 kg (OR 2.27) birthweight > 4 kg
shoulder dystocia (OR 1.90)
occipito-posterior position (RR 2.44)
prolonged second stage of labour:
 duration 2 -3 hours (RR 1.47)
 duration 3 - 4 hours (RR 1.79)
 duration > 4 hours (RR 2.02)
instrumental delivery:1
 ventouse without episiotomy (OR 1.89)
 ventouse with episiotomy (OR 0.57)
 forceps without episiotomy (OR 6.53)
 forceps with episiotomy (OR 1.34).
forceps delivery
prevention of OASIS injury?
Episiotomy
 Some studies have shown a protective effect while others have not (conflicting evidence)
 Mediolateral episiotomy should be considered in instrumental deliveries (protective).
 A mediolateral episiotomy technique is recommended, angle is 60 degrees away from the
midline when the perineum is distended.

4. 4 Dr Muhamed Al Bellehy MD
Dr Muhamed Al Bellehy MD
o NICE recommends an angle of 45–60 degrees from the midline (to  incidence of OASIS).
 the resultant suture angle of 40–60 degrees is more important than the incision
angle of 45–60 degrees
 this can be difficult to achieve at ‘crowning’ when the perineum is fully stretched.
 An episiotomy performed at 40 degrees results in a post-delivery angle of 22 degrees,
which is too close to the midline to be maximally protective
 A 60-degree episiotomy from the centre of the introitus results in a post-delivery
angle of 45 degrees.
o Special scissors designed to ensure an incision angle of 60 degrees (effective)
Perineal protection
 Perineal protection at crowning can be protective.
 NICE  no difference between ‘hands poised’ & ‘hands on’ the perineum as prevention for OASIS.
 more recently  recommend, manual perineal protection/ ‘hands on’ techniques ( OASIS rates).
o These include:
 Left hand slowing down the delivery of the head.
 Right hand protecting the perineum.
 Mother NOT pushing when head is crowning (communicate).
 Think about episiotomy (risk groups and correct angle).
Hands placement in the (A) Finnish manual perineal protection (FMPP) and (B) Viennese manual perineal
protection (VMPP)
 the Ritgen manoeuvre VS ‘standard care’ The best method is unclear,
o Ritgen manoeuvre (delivering fetal head, using one hand to pull the fetal chin from between the
maternal anus and the coccyx and the other on the fetal occiput to control speed of delivery)
o ‘standard care’ (not specifically defined but it included perineal protection/‘hands on’).
Warm compress
 Warm compression during the second stage of labour reduces the risk of OASIS
 By holding the compress on the perineum continuously during and between contractions.
Perineal massage during antenatal period and in second stage of labour
 Perineal massage during the last month of pregnancy has been suggested as a possible way of enabling
perineal tissue to expand more easily during birth.
 Women practising perineal massage were less likely to have an episiotomy (only in women without
previous vaginal birth only)
 protective effect of perineal massage in the second stage of labour _ inconclusive data.

5. 5 Dr Muhamed Al Bellehy MD
Dr Muhamed Al Bellehy MD
Identification of obstetric anal sphincter injuries
 All women having a vaginal delivery are at risk of sustaining OASIS or isolated rectal
buttonhole tears.
 identification of obstetric anal sphincter injuries
o before assessing for genital trauma (NICE perineal care guidance),
 healthcare professionals should:
 Explain to the woman what they plan to do and why
 offer inhalational analgesia
 ensure good lighting
 position woman so that she is comfortable - to allow adequate assessment of the
trauma and for the repair itself
o usually be in the lithotomy position
o systematic examination, including a digital rectal examination, to assess the severity of damage
 Systematic assessment of genital trauma should include:
 explanation of what the healthcare professional plans to do and why
 confirmation by the woman that effective local or regional analgesia is in place
 visual assessment of the extent of perineal trauma to include involved
structures, apex of the injury and degree of bleeding
 a rectal examination to assess whether there has been any damage to the
external or internal anal sphincter if there is any suspicion that the perineal
muscles are damaged.
 How can the identification of OASISinjuries be improved?
o The woman should be referred to a more experienced healthcare professional if uncertainty
exists as to the nature or extent of the trauma sustained.
o healthcare professionals should attend hands-on training in perineal assessment and repair.
o anal sphincter and anorectal mucosal injury cannot be excluded without performing a rectal
examination.
o endoanal ultrasound
 sonographic abnormalities of anal sphincter (‘occult’ injuries) in 33% of women
following vaginal delivery.
 detection rate immediately following delivery was not significantly increased compared
with clinical examination alone.
 As there are current limitations in availability, image quality, interpretation skills and
patient acceptability, the use of endoanal ultrasound in detecting OASIS immediately
after delivery should be viewed as a RESEARCH TOOL

6. 6 Dr Muhamed Al Bellehy MD
Dr Muhamed Al Bellehy MD
Repair
William’s
25
th
edition
Timing of repair
 perineal repairs are deferred until the placenta has been delivered.
 advantage of This policy
o permits undivided attention to the signs of placental separation and delivery.
o repair is not interrupted or disrupted by placenta delivery. This is especially true if manual
removal must be performed.
 disadvantage  continuing blood loss until the repair is completed. Direct pressure from an applied
gauze sponge will help to limit this volume.
FIRST-DEGREE LACERATIONS do not always require repair
sutures are placed to control bleeding or restore anatomy.
few data guide suture selection
fine-gauge absorbable or delayed-absorbable suture or adhesive glue is suitable.
SECOND-DEGREE LACERATIONS OR EPISIOTOMY REPAIR
FIGURE 27-15
Mediolateral episiotomy repair. A. The
vaginal epithelium and deeper tissues are
closed with a single, continuous, locking
suture. The angle seems less acute now
(approximately 45°) since the perineum is
no longer distended.
B. After the vaginal component of the
laceration is repaired, deeper perineal
tissues are reapproximated by a single,
continuous, nonlocking suture. Small
episiotomies may not require this deeper
layer. C. With a similar continuous,
nonlocking technique, the superficial
transverse perineal and bulbospongiosus
muscles are reapproximated. D. Last, the
perineal skin is closed using a subcuticular
stitch.

7. 7 Dr Muhamed Al Bellehy MD
Dr Muhamed Al Bellehy MD
FIGURE 27-16 Midline episiotomy repair. A.
An anchor stitch is placed above the wound
apex to begin a running, locking closure
with 2–0 suture to close the vaginal
epithelium and deeper tissues and
reapproximate the hymeneal ring. B. A
transition stitch redirects suturing from the
vagina to the perineum.
C. The superficial transverse perineal and
bulbospongiosus muscles are
reapproximated using a continuous,
nonlocking technique with the same length
of suture. This aids restoration of the
perineal body for long-term support. D. The
continuous suture is then carried upward
as a subcuticular stitch. The final knot is
tied proximal to the hymeneal ring.
Evidence – WILLIAM’S -- --- - - - - -- most studies support
 a continuous suturing, rather than placing interrupted
o faster than interrupted sutures
o with few exceptions, yields less pain.
 Blunt needles  likely decrease the incidence of needle-stick injuries.
 Commonly used suture materials are 2–0 polyglactin 910 (Vicryl) or chromic catgut.
o Vicryl  decrease in postsurgical pain and lower risk of wound dehiscence.
o Closures with traditional polyglactin 910 occasionally require removal of residual
suture from the repair site because of pain or dyspareunia. This disadvantage may be
reduced by using a rapidly absorbed polyglactin 910 (Vicryl Rapide)
repair of OASIS injury
 Who should repair OASIS injury?
 Personnel
o by a trained practitioner or by a trainee under supervision
 Inexperienced attempts may contribute to maternal morbidity, especially anal
incontinence
o Formal training in OASIS repair techniques should be an essential component of obstetric
training. (in the module on postpartum problems in RCOG core training log book)
o Involvement of a colorectal surgeon will be dependent on local protocols, expertise and
availability as the majority of colorectal surgeons are not familiar with acute OASIS
 Place of care = Repair in
 operating theatre  allow the repair to be performed under optimal conditions with appropriate
instruments, adequate light & an assistant
 delivery room in certain circumstances after discussion with a senior obstetrician.
 anaesthesia - under regional or general
o this will facilitate identification of full extent of the injury and enable retrieval of the
retracted ends of the torn anal sphincter
o locally injected lidocaine can be used solely or as a supplement to bilateral pudendal nerve blockade.

8. 8 Dr Muhamed Al Bellehy MD
Dr Muhamed Al Bellehy MD
 Technique
o If there is excessive bleeding vaginal pack, urgent repair.
o A rectal examination after the repair
 to ensure that sutures have not been inadvertently inserted through anorectal
mucosa. If so, a suture should be removed.
Repair of 4th-degree laceration
Repair of anorectal mucosa
1. Suturing of the anorectal mucosa begins
above the laceration apex by 1 cm
2. Sutures are placed through the anorectal
submucosa approximately 0.5 cm apart
down to the anal verge
do not enter the anorectal lumen
3. using a continuous, nonlocking method
IAS is repaired before the EAS
4. IAS may retract laterally – the torn ends of IAS must
be sought & retrieved for repair
IAS can be identified as the glistening
white fibrous structure lying
between the anal canal submucosa
and the fibers of the external anal
sphincter.
5. A second reinforcing layer using sutures in
a continuous, nonlocking fashion.
Repair
of
3
rd
-degree
laceration
repair of EAS
6. disrupted ends of the striated EAS muscle and capsule are identified
and grasped.
7. end-to-end approximation of the external anal sphincter (EAS) 
a suture is placed through the EAS muscle + simple interrupted sutures are
placed at the 3, 6, 9, and 12 o’clock positions through the perisphincter
connective tissue.
 The first suture is placed posteriorly to maintain clear
exposure.
 Another suture is then placed inferiorly at the 6 o’clock
position.
 The sphincter muscle fibers are next reapposed by a figure-
of-eight stitch.
 Last, the remainder of the fascia is closed with a stitch
placed anterior to the sphincter cylinder and again with
once placed superior to it
the strength of this closure is derived from the connective
tissue surrounding the sphincter—often called the capsule—
and not the striated muscle.
 For repair of a full thickness EAS tear end-to-end technique vs overlapping technique
 end-to-end technique, preferred by William’s
 the overlapping technique, only for type 3c lacerations
o the ends of the external anal sphincter are brought to the midline and lie atop one another.
o Two rows of mattress sutures travel through both sphincter ends to recreate the anal ring.
NB: overlapping of partial thickness EAS tears would exert undue tension on the repair
RCOG an overlapping an end-to-end
perineal pain, Dyspareunia, flatus incontinence, QOL no difference at 12 months
faecal urgency, anal incontinence score
risk of deterioration of anal incontinence symptoms
lower incidence at 12 months for the overlapping

9. 9 Dr Muhamed Al Bellehy MD
Dr Muhamed Al Bellehy MD
William’s neither yields superior long-term anatomical or functional results
RCOG 2015 anorectal mucosa IAS EAS
sutures full thickness partial thickness
(3a & some 3b)
continuous or separate
repair
continuous or interrupted Only separate repair
 anal incontinence
interrupted or
mattress sutures
Interrupted Interrupted
Not figure of eight
because they are haemostatic in nature and may cause tissue ischaemia.
technique end-to-end yes Yes can be used for all EAS tears
Overlap No No Yes No
suture materials 3-0 polyglactin
Not PDS
braided sutures such as 2-0 polyglactin
monofilament sutures such as 3-0 PDS
surgical knot when catgut is used  knot tied
within anal canal to  tissue reaction
& infection
With polyglactin suture  no longer
necessary as it dissolves by hydrolysis
- sutures should not be inserted through
anorectal mucosa
burying of surgical knots beneath superficial perineal
muscles
For anorectal mucosa PDS sutures may cause more irritation & discomfort as they take longer to dissolve than polyglactin
the use of fine suture sizes such as 3-0 PDS & 2-0 polyglactin (Vicryl®) may cause less irritation and discomfort
from William’s
 evidence-based data suggest delayed-absorbable material can provide sustained tensile strength during
healing. Jallad and coworkers (2016),  higher perineal breakdown rate following OASIS repair with chromic gut.
 For OASIS repairs, burying of surgical knots beneath the superficial perineal muscles is
recommended to  risk of knot and suture migration to the skin.
Suture migration
 Dx= complains of irritation/pain around the perineum + exposed ends of suture material are seen or
felt.
 incidence  7%.
 Prevention - trimming suture ends and burying the knots in the deep and superficial perineal muscles
 Exposed suture ends can be trimmed in the outpatient setting under local anaesthesia.
10. Postoperative management
 Initially, locally applied ice packs help reduce swelling and allay discomfort (de Souza Bosco Paiva, 2016). In
subsequent days, warm sitz baths aid comfort and hygiene.
 a small squirt bottle of warm water can cleanse the site after voiding or stooling.
RCOG Recommendations Comment
broad-spectrum antibiotics recommended to reduce postoperative infections and wound dehiscence (based on
one small trial)
ACOG (2016c).==> a single dose of ANTIBIOTIC at the time
of repair
second-generation cephalosporin is suitable, or clindamycin for
penicillin-allergic women

10. 10 Dr Muhamed Al Bellehy MD
Dr Muhamed Al Bellehy MD
Laxatives and stool softeners Recommended such as lactulose for about 10 days - dose should be titrated to keep the
stool soft but not loose
to reduce risk of wound dehiscence (passage of a hard stool may
disrupt the repair)
earlier and less painful bowel motion and earlier postnatal discharge
Bulking agents such as ispaghula
husk
not be given routinely
with laxatives
lactulose alone vs lactulose + ispaghula husk  incontinence in
immediate postpartum period was more frequent with the latter regime
Physiotherapy could be beneficial
early home biofeedback therapy
enemas and suppositories are
avoided.
Not recommended
ANALGESICS  topical of 5-% LIDOCAINE OINTMENT
o not effective in one randomized trial (Minassian, 2002).
 ORAL codeine provide.
 NSAID tablets.
Intercourse For those with second-degree lacerations or OASIS,
intercourse is usually proscribed until after the first
puerperal visit at 6 weeks.
follow-up pain may signal a large vulvar, paravaginal, or ischiorectal
fossa hematoma or perineal cellulitis
these sites should be examined carefully if pain is severe or
persistent.
at a convenient time (6–12 weeks
postpartum)
Recommended review should be by clinicians with a special interest in OASIS.
If available- endoanal ultrasonography & anal manometry
referral to a specialist gynaecologist
or colorectal surgeon
Recommended If a woman is experiencing incontinence or pain
Prognosis
o 60–80% of women are asymptomatic 12 months following delivery and EAS repair.
o normal function is not always ensured even with correct and complete surgical repair. Some women may
experience continuing fecal incontinence caused by injury to the innervation of the pelvic floor musculature
(Roberts, 1990).
o the best method of delivery following OASIS- --------------
o no systematic reviews or randomised controlled trials
o Short-term follow-up of a cohort of 73 women showed that the women who underwent vaginal
delivery suffered no significant deterioration in anal sphincter function or quality of life
o All women should be counselled about the mode of delivery (and documented)
risk after a subsequent delivery
risk of a further 3rd
- or 4th
-degree tear 5–7%
Risk of worsening faecal symptoms 17%
This seemed to occur if there had been faecal incontinence beyond 3 months
but resolution by 6 months after the index delivery
o The role of prophylactic episiotomy in subsequent pregnancies is not known and therefore an
episiotomy should only be performed if clinically indicated.

11. 11 Dr Muhamed Al Bellehy MD
Dr Muhamed Al Bellehy MD
Risk management
What processes and policies should be in place for women who have sustained obstetric OASIS?
o Units should have a clear protocol for the management of OASIS.
o Documentation of the anatomical structures involved, the method of repair and the suture
materials should be made.
o The woman should be fully informed about the nature of her tear and the offer of follow-up
should be made, all supported by relevant written information.
o failure to identify the injury after delivery anal incontinence and rectovaginal and anovaginal fistulae.
o At present, the occurrence of OASIS is not considered substandard care because it is a known
complication of vaginal delivery.
o Failure to recognise OASIS damage or carry out an adequate repair may be considered substandard care.
A poor technique, poor selection of materials or poor healing may cause a repair to fail.