Case 91: Perineal tear

 CASE 91: PERINEAL TEAR

History

A woman has just delivered her second baby on the labour ward. She is 37 years old and had a

previous premature delivery at 34 weeks. In this pregnancy she went into spontaneous labour

at 38 weeks after an uncomplicated pregnancy.

The symphysiofundal height was consistent with dates until 37 weeks when the midwife measured it as 41 cm. However before an ultrasound scan for growth and liquor volume could be

arranged the woman went into spontaneous labour.

At the time of admission she was 5 cm dilated and spontaneous rupture of membranes

occurred soon after. The baby was delivered 30 min later in the direct occipitoanterior position.

The placenta was delivered by controlled cord traction, after which the midwife noticed a

perineal tear. The tear extended from the introitus in the midline and she could see torn

muscle fibres suggestive of the torn ends of the external anal sphincter. She has called you to

review the patient.

Questions

• What is the likely diagnosis?

• What factors predispose to this condition?

• How would you manage this patient?100 Cases in Obstetrics and Gynaecology

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ANSWER 91

The history suggests a third-degree tear.

! Classification of perineal tears

• First degree: injury to the perineum involving the epithelium or skin but not the

perineal muscles

• Second degree: injury to the perineum involving perineal muscles but not involving the anal sphincter

• Third degree: injury to the perineum involving the anal sphincter complex (external anal sphincter (EAS) and internal anal sphincter (IAS)):

• 3a: less than 50 per cent of EAS thickness torn

• 3b: more than 50 per cent of EAS thickness torn

• 3c: IAS torn

• Fourth degree: injury to the perineum involving the anal sphincter complex (EAS

and IAS) and rectal mucosa

Risk factors

A third-degree tear occurs in 2–4 per cent of women, and is more common in the following circumstances:

• birthweight over 4 kg

• persistent occipitoposterior position

• nulliparity

• induction of labour

• epidural

• second stage of labour lasting more than 1 h

• episiotomy

• forceps delivery.

Third-degree tear diagnosis depends on the vigilance of the person inspecting a tear and may

easily be missed. This has far-reaching consequences, as failure to perform adequate primary

repair may increase the chance of longer-term faecal incontinence.

Management

• The woman should be transferred to theatre for repair. This enables adequate analgesia (spinal or epidural), good exposure, good lighting and availability of appropriate instruments.

• The tear should be repaired in layers:

• rectal mucosa (if involved)

• internal anal sphincter (if involved)

• external anal sphincter

• perineal muscle

• vaginal epithelium

• perineal skin.

• Broad-spectrum antibiotics should be administered to prevent infection from possible contamination by bowel organisms.

• Laxatives should be administered to prevent constipation that might compromise

the repair.Case 91: Perineal tear

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• Adequate postoperative analgesia is needed.

• The woman should not generally be discharged until she has opened her bowels.

• A follow-up appointment should be made after approximately 6 weeks to ensure

that the woman has no significant bowel symptoms and to refer on to a colorectal

specialist if she has.

• Elective caesarean section should be discussed as a possibility for any subsequent

deliveries.

KEY POINTS

• Following delivery any vaginal tear must be inspected carefully to ensure that the

anal sphincter is not disrupted.

• Any third-degree tears should be repaired in theatre by an experienced operator

to avoid future problems with faecal incontinence.