Anal sphincter injury at childbirth

Which cup for which position? Metal cups appear to be more suitable for occipitoposterior, transverse, and difficult occipitoanterior position deliveries.²⁸

Soft cups seem appropriate for straightforward deliveries, as they are significantly more likely to fail to achieve vaginal delivery (OR 1.65; 95% CI, 1.19 to 2.29). Though scalp injury was less likely with soft cups (OR 0.45; 95% CI, 0.15 to 0.60), the 2 groups did not differ in maternal injury.

Let mother choose position—it’s not critical

Women should be encouraged to deliver in whichever position is most comfortable. Though some evidence suggests that perineal injury is more likely with a standing position delivery, a Cochrane review found that, with the possible exception of increased blood loss, there were no deleterious effects to the mother or fetus.²⁹

The current evidence on various delivery positions is inconclusive.

Tactics for management of anal sphincter injury

Recognition and proper classification. Examination of perineal injury under adequate analgesia and light, and a combined vaginal and rectal examination are essential to assess the degree of anal sphincter injury.

If any doubt exists about the extent of the injury, a second opinion must be sought. It has been reported that the presence of an experienced person at the time of perineal assessment has increased the detection rate of anal sphincter injury.

Immediate repair of the perineal injury is advisable compared to delayed repair, as the immediate repair will reduce the bleeding and pain associated with the injury, which may in turn affect early breastfeeding and bonding. Immediate repair also prevents the development of edema (which may hinder subsequent recognition of structures involved) and reduces the possibility of infection.

Careful examination of the labia, clitoris, and urethra is essential to identify any injury. These structures need repair prior to the perineal repair.

Only a doctor experienced in anal sphincter repair or a trainee under supervision should perform a repair.

I prefer to repair the injury in the operating theater, where there is access to good lighting, appropriate equipment, and aseptic conditions.

General or regional (spinal, epidural, caudal) anesthesia is an important prerequisite—particularly for overlap repair, as the inherent tone in the sphincter muscle can cause the torn muscle ends to retract within the sheath. Muscle relaxation is necessary to retrieve the ends and overlap without tension.

The woman is placed in the lithotomy position and the full extent of the injury is evaluated by careful vaginal and rectal examination.

In the presence of a 4th-degree tear, the torn anal epithelium is repaired with interrupted 3/0 polyglactin (Vicryl, Ethicon, Somerville, NJ) sutures, with the knots tied in the anal lumen. Another option: A subcuticular repair of the anal epithelium using 3/0 polyglactin via the transvaginal approach has been used with equal success.

The sphincter muscles are repaired with 3/0 polydioxanone sulphate (PDS) clear sutures. Compared to a braided suture, these monofilamentous sutures are less likely to precipitate infection.

The internal anal sphincter should be identified and any tear repaired separately from the external sphincter, with interrupted 3/0 PDS. I advocate primary surgical repair of the internal sphincter, which has been shown to be beneficial in patients with established anal incontinence.

The external anal sphincter should be repaired with 3/0 PDS sutures, with either end-to-end or overlapping technique. No published randomized studies at present suggest that primary overlap technique is better than primary end-to-end technique. However the secondary overlapping techniques carried out by coloproctologists have shown better continence rates compared to secondary end-to-end technique.

Extra attention should be directed to reconstructing the perineal muscles, to provide support to the sphincter repair and maintain the vaginoanal distance. This may offer some protection in subsequent vaginal delivery and may prevent suture migration.

A vaginal and rectal examination must be performed and swabs and needles should be checked.

Intravenous antibiotics should be commenced intraoperatively and continued orally for 1 week.

A stool softener (lactulose 10 mL, 3 times daily) and a bulking agent should be prescribed for at least 2 weeks post-operatively, as passage of a large bolus of hard stool may disrupt the repair.

A comprehensive record should be documented, together with a diagram to demonstrate the injury.

The woman should be informed of the injury and the possible sequelae.

It is usual to ensure that a bowel action has occurred prior to discharge.

A hospital follow-up by an experienced doctor is essential.

Obstetric anal sphincter injury by the numbers