Key Implications

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  Between one-third and two-thirds of women who sustain a recognized third-degree tear during delivery subsequently suffer from fecal incontinence.

  
  
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  The prevalence of anal incontinence (including flatus as a sole symptom) and faecal incontinence (with or without flatus) following end-to-end repair ranges between 15% and 61% (mean = 39%) and between 2% and 29% (mean = 14%) respectively. In addition, faecal urgency can affect a further 6%–28% [5].

  
  
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  Persistent sonographic anal sphincter defects are identified in 34%–91%.

  
  
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  Following OASIS, anal incontinence during coitus affects about 17% of women.

  
  
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  Compared with women with a minor (grade 3a/3b) tear, those with a major (grade 3 c/4) one have a significantly poorer outcome with respect to defecatory symptoms and quality of life (QoL), as well as anal manometry. Women with major tears are significantly more likely to have an endosonographic isolated internal anal sphincter (IAS) or combined IAS and external anal sphincter (EAS) defect. Combined defects are associated with a higher risk of fecal incontinence and lower anal canal pressures [8].

  
  
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  Women with OASIS are at increased risk of developing long-term anal incontinence (58.8%) as well as fecal incontinence (30.6%) [9].

  
  
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  Compared to controls, more women with OASIS report stress urinary incontinence (33 vs. 14%; p = 0.002; OR: 3.06; CI: 1.54–6.07) and overall urinary incontinence (21.2 vs. 38%, p = 0.005) and have worse quality of life (QoL) scores. At 10 weeks after delivery the adjusted odds ratio (OR) for stress urinary incontinence (SUI) is 2.65 (1.22–5.74) [10].

Long Term

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  Subjective and objective anal function after anal sphincter injury deteriorates further over time and with subsequent vaginal deliveries. A thin perineal body and internal sphincter injury seem to be important for continence and anal pressure.

  
  
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  Women who sustained OASIS have no further deterioration in urinary or sexual symptoms 18 years after delivery [11].

Key Pointers

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  Instrumental delivery, prolonged duration of the second stage of labour, nulliparity, increased birthweight, shoulder dystocia, persistent occipito-posterior position, epidural anesthesia, labour induction, labour augmentation and midline episiotomy are major risk factors [12].

  
  
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  The angle of mediolateral episiotomy is significantly narrower in women who sustain OASIS.

  
  
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  The perineal length is significantly shorter in women who sustain perineal tears and OASIS.

Key Diagnostic Signs

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  Following informed consent, a vaginal and rectal examination is performed with adequate analgesia.

  
  
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  Visual inspection of the genitalia is followed by digital vaginal examination to establish the extent of the vaginal tear(s) and the apex. With the labia parted, assessment of the anal sphincter and exploration for rectovaginal perforations (buttonhole tears) is undertaken by a digital examination of the anal canal and the rectum.

  
  
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  With the index finger in the anal canal and the thumb in the vagina, the EAS can be palpated circumferentially and the extent and the depth of the tear further ascertained.

  
  
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  Clinical diagnosis of OASIS can be suboptimal. Studies with endoanal ultrasound have shown that ‘occult’ OASIS is common after vaginal delivery, ranging between 20% and 41%.

  
  
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  However, are these injuries truly occult or unrecognized at delivery? In women whose perineum is re-examined by an experienced person clinically and/or by endoanal ultrasound the prevalence of OASIS increases more than two-fold.

  
  
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  Most sphincter defects considered as ‘occult’ injuries are actually injuries that should have been clinically diagnosed but were missed. Although 98.8% of OASIS can be detected clinically at the time of delivery, the use of endoanal ultrasound shows that midwives can miss 87% of injuries and doctors 28% [13].

  
  
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  As endoanal ultrasound is a technique that requires equipment and expertise, the diagnosis rests on clinical assessment and in practice, postpartum anal endosonography is of limited value.

Key Actions (Management Algorithm)

The following surgical principles should be followed when performing perineal repairs:

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  Check equipment and count swabs and instruments before and after the repair.

  
  
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  The woman should be placed in a comfortable position with proper lighting for adequate exposure of the perineum.

  
  
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  Ensure the woman has effective anaesthesia.

  
  
  
  
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     ◦ 10–20 mL of lignocaine 1% is injected into the perineal wound. If the woman has an epidural, it may be ‘topped-up’.

     
     
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     ◦ In cases of extensive tears or OASIS a general or regional anaesthesia will ensure muscle relaxation for proper evaluation and repair of the injury.

  
  
  
  
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  The injury should be evaluated in the lithotomy position and graded according to the recommended classification.

  
  
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  The repair should be undertaken under aseptic conditions.

  
  
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  Polyglactin 910 (Vicryl®, Ethicon, Edinburgh, UK) and more rapidly absorbable polyglactin 910 material (Vicryl Rapide®) are the two most common absorbable synthetic suture materials used for perineal repair. The tensile strength of Vicryl Rapide® is reduced in 10–14 days and it is completely absorbed in 42 days. Vicryl Rapide® is associated with a significant reduction in the need for suture removal up to 3 months postpartum.

Repair of Episiotomy: First- and Second-Degree Tears

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  First-degree tears and labial lacerations can be left unsutured, unless there is excessive bleeding or concerns about the anatomical alignment and healing. In unsutured bilateral labial lacerations there is a risk of labial adhesions and voiding difficulties.

  
  
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  The trauma should be repaired using a continuous non-locking technique to reapproximate all layers (vagina, perineal muscles and skin).

  
  
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  First, a continuous layer is inserted to close the vaginal trauma, commencing above the vaginal apex of the wound and finishing at the level of hymen with a loop knot.

  
  
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  The needle is then inserted into the vaginal skin and emerges through the perineal muscles to reconstruct the fourchette.

  
  
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  The perineal muscles are reconstructed with continuous non-locking suturing. If the trauma is deep, the perineal muscles can be closed in two layers (a deep interrupted layer may be required).

  
  
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  At the inferior end of the wound, the suturing direction is reversed and continuous sutures are applied in the subcutaneous tissue. The repair is then completed with a loop or Aberdeen knot at the level of the hymenal remnants. The skin may also be closed using interrupted transcutaneous sutures.

  
  
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  Optimal alignment of the muscles avoiding undue tension ensures reapproximation of the perineal skin edges. Leaving the perineal skin unsutured may reduce superficial dyspareunia.

Repair of OASIS

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  The most common techniques for primary repair following OASIS are ‘end-to-end’ with interrupted sutures [14] and overlap repairs. Consensus is still lacking as significant heterogeneity is noted among studies [15]. Overlap repair of the EAS with separate end-to-end repair of the IAS showed promising results when introduced with a reduction of anal incontinence from 41% to 8% compared with matched historical controls who had an end-to-end repair [16].

  
  
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  Several studies have evaluated the two techniques with varying results and a Cochrane review concluded that although ‘immediate primary overlap repair of the external anal sphincter compared with immediate primary end-to-end repair appears to be associated with lower risks of developing faecal urgency and anal incontinence symptoms, at the end of 36 months there appears to be no difference in flatus or faecal incontinence between the two techniques’[17].

  
  
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  Repair of OASIS should be conducted in the operating theatre with assistance, good lighting, equipment and aseptic conditions.

  
  
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  A ‘buttonhole’ tear without injury of the anal sphincter is repaired transvaginally using interrupted Vicryl sutures in layers including repair of the rectovaginal fascia to reduce the risk of healing defects and rectovaginal fistula.

  
  
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  In fourth-degree tears, the torn anal epithelium is repaired with interrupted Vicryl 3/0 sutures with the knots tied in the anal lumen to reduce the suture material within the tissue.

  
  
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  The sphincter muscles are repaired with 3/0 PDS as monofilament sutures carry lower risks of infection. Complete absorption of PDS takes longer than Vicryl, with 50% tensile strength lasting more than 3 months compared to 3 weeks. However, a randomised controlled trial revealed no differences in suture-related morbidity between Vicryl and PDS at 6 weeks postpartum[18].

  
  
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  The IAS should be identified and, if torn, repaired by an end-to-end repair with interrupted or mattress 3/0 PDS sutures.

  
  
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  As the torn ends of the EAS tend to retract they should be identified with Allis forceps and overlapped using PDS 3/0 sutures.

  
  
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  If the EAS is only partially torn (grade 3a/3b), an end-to-end repair is technically more feasible using two or three mattress sutures similar to IAS repair.

  
  
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  After repair of the sphincter, the vaginal skin and the perineal muscles should be sutured and the perineal skin approximated with a Vicryl 3/0 subcuticular suture.

  
  
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  After completion of the procedure, a vaginal and rectal examination should confirm haemostasis and a complete repair, ensure that all instruments and swabs have been removed and exclude inadvertent insertion of sutures through the rectal mucosa.

  
  
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  The woman should be informed of the injury and given instructions about analgesia, hygiene, the importance of diet and avoidance of constipation and about pelvic floor exercises. She should be given contact details if she develops any symptoms during the postnatal period with access to a perineal specialist or clinic.

  
  
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  A detailed documentation with a diagram should be included in the case notes.

  
  
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  Intraoperative and postoperative antibiotics following repair of OASIS for 5–7 days are essential to minimize risks of infection and wound breakdown, which may result in incontinence or fistula formation.

  
  
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  An indwelling urethral catheter should be left in situ for about 24 hours as perineal pain and regional anaesthesia may cause voiding difficulty or reduced bladder sensation.

  
  
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  The degree of pain following perineal trauma is related to the extent of the injury.

  
  
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  In extensive perineal tears or OASIS, stool softeners (lactulose and a bulking agent, i.e., Fybogel) for 10–14 days should be prescribed, to avoid constipation and wound disruption.

  
  
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  Women who sustain OASIS should be assessed in a perineal clinic by a senior obstetrician or a specialist midwife 6–8 weeks after delivery. A pelvic examination is performed, to look for healing defects, scarring, granulation tissue and tenderness. Subsequently women should be scheduled for anal manometry and endoanal ultrasonography.

  
  
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  The women are advised to continue pelvic floor exercises supervised by a pelvic floor physiotherapist.