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Obstetric anal sphincter injury: 7 critical questions about care

OBG Manag. 2008 February;20(2):56-68

Ranee Thakar, MD, MRCOG

When and how you manage an injury determines the patient’s quality of life. Here are 7 issues to consider.

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IN THIS ARTICLE

Is endoanal US helpful?
Repair technique for internal and external sphincters
How to code for obstetric anal sphincter injury

References

1. Sultan AH, Kettle C. Diagnosis of perineal trauma. In: Sultan AH, Thakar R, Fenner DE, eds. Perineal and Anal Sphincter Trauma. London: Springer; 2007:13-19.

2. Sultan AH, Thakar R. Third and fourth degree tears. In: Sultan AH, Thakar R, Fenner DE, eds. Perineal and Anal Sphincter Trauma. London: Springer; 2007:33-51.

3. Sultan AH. Primary repair of obstetric anal sphincter injury. In: Staskin DR, Cardozo L, ed. Textbook of Female Urology and Urogynaecology. London: ISIS Medical Media; 2006.

4. Thakar R, Fenner DE. Anatomy of the perineum and the anal sphincter. In: Sultan AH, Thakar R, Fenner DE, eds. Perineal and Anal Sphincter Trauma. London: Springer; 2007:1-12.

5. Faltin DL, Boulvain M, Floris LA, Irion O. Diagnosis of anal sphincter tears to prevent fecal incontinence: a randomized controlled trial. Obstet Gynecol. 2005;106:6-13.

6. Andrews V, Thakar R, Sultan AH. Occult anal sphincter injuries—myth or reality. Br J Obstet Gynaecol. 2006;113:195-200.

7. Sultan AH. Obstetric perineal injury and anal incontinence. Clin Risk. 1999;5:193-196.

8. Royal College of Obstetricians and Gynaecologists. Management of third and fourth degree perineal tears following vaginal delivery. Guideline 29. London: RCOG Press; 2001.

9. Norton C, Christensen J, Butler U, et al. Anal Incontinence. 2nd ed. Plymouth: Health Publication Ltd; 2005:985-1044.

10. Sultan AH, Thakar R. Lower genital tract and anal sphincter trauma. Best Pract Res Clin Obstet Gynaecol. 2002;16:99-116.

11. Williams A, Adams EJ, Tincello DG, Alfirevic Z, Walkinshaw SA, Richmond DH. How to repair an anal sphincter injury after vaginal delivery: results of a randomised controlled trial. BJOG. 2006;113:201-207.

12. Fernando RJ, Sultan AH, Kettle C, Radley S, Jones P, O’Brien PMS. Repair techniques for obstetric anal sphincter injuries. A randomized controlled trial. Obstet Gynecol. 2006;107:1261-1268.

13. Fernando R, Sultan AH, Kettle C, Thakar R, Radley S. Methods of repair for obstetric anal sphincter injury. Cochrane Database Syst Rev. 2006;3:CD002866.-

14. Fernando RJ, Sultan AH, Radley S, Jones PW, Johanson RB. Management of obstetric anal sphincter injury: a systematic review and national practice survey. BMC Health Serv Res. 2002;2:9.-

15. MacArthur AJ, MacArthur C. Incidence, severity, and determinants of perineal pain after vaginal delivery: a prospective cohort study. Am J Obstet Gynecol. 2004;191:1199-1204.

16. Hedayati H, Parsons J, Crowther CA. Rectal analgesia for pain from perineal trauma following childbirth. Cochrane Database Syst Rev. 2003;(3):CD003931.-

17. Kettle C, Hills RK, Jones P, Darby L, Gray R, Johanson R. Continuous versus interrupted perineal repair with standard or rapidly absorbed sutures after spontaneous vaginal birth: a randomised controlled trial. Lancet. 2002;359:2217-2223.

18. Sultan AH, Monga AK, Kumar D, Stanton SL. Primary repair of obstetric anal sphincter rupture using the overlap technique. Br J Obstet Gynaecol. 1999;106:318-323.

19. Mahony R, Behan M, O’Herlihy C, O’Connell PR. Randomized, clinical trial of bowel confinement vs. laxative use after primary repair of a third-degree obstetric anal sphincter tear. Dis Colon Rectum. 2004;47:12-17.

20. Thakar R, Sultan A. Postpartum problems and the role of a perineal clinic. In: Sultan AH, Thakar R, Fenner DE, eds. Perineal and Anal Sphincter Trauma. London: Springer; 2007:65-79.

21. Williams A, Lavender T, Richmond DH, Tincello DG. Women’s experiences after a third-degree obstetric anal sphincter tear: a qualitative study. Birth. 2005;32:129-136.

22. Fynes M, Donnelly V, Behan M, O’Connell PR, O’Herlihy C. Effect of second vaginal delivery on anorectal physiology and faecal continence: a prospective study. Lancet. 1999;354:983-986.

23. Scheer I, Thakar R, Sultan A. Should women who sustained obstetric anal sphincter injuries be allowed a vaginal delivery? Neurourol Urodynam. 2006;25:512-513.

24. Peleg D, Kennedy CM, Merrill D, Zlatnik FJ. Risk of repetition of a severe perineal laceration. Obstet Gynecol. 1999;93:1021-1024.

25. Harkin R, Fitzpatrick M, O’Connell PR, O’Herlihy C. Anal sphincter disruption at vaginal delivery: is recurrence predictable? Eur J Obstet Gynaecol Reprod Biol. 2003;109:149-152.

26. Coats PM, Chan KK, Wilkins M, Beard RJ. A comparison between midline and mediolateral episiotomies. Br J Obstet Gynaecol. 1980;87:408-412.

27. Thakar R, Eason E. Prevention of perineal trauma. In: Sultan AH, Thakar R, Fenner DE, eds. Perineal and Anal Sphincter Trauma. London: Springer; 2007:52-64.

28. Johanson RB, Rice C, Doyle M. A randomised prospective study comparing the new vacuum extractor policy with forceps delivery. Br J Obstet Gynaecol. 1993;100:524-530.

29. Bofill JA, Rust OA, Schorr SJ, et al. A randomized prospective trial of the obstetric forceps versus the M-cup vacuum extractor. Am J Obstet Gynecol. 1996;175:1325-1330.

Fast Track

A rectal examination with digital palpation is always necessary to determine the extent of injury

Obstetric anal sphincter injury is best detected clinically immediately after delivery

Repair torn anal epithelium with interrupted Vicryl 3-0 sutures, with the knots tied in the anal lumen

Repair the internal and external anal sphincters separately

Avoid codeine-based analgesia because it can cause constipation and lead to excessive straining and disruption of the repair

Any woman who sustains anal sphincter injury should be examined by a senior obstetrician 6 to 8 weeks after delivery

There is no evidence that routine episiotomy prevents recurrent anal sphincter injury

Cesarean delivery is recommended for women who have some degree of anal sphincter compromise, even if their symptoms are controlled

If operative vaginal delivery is required, vacuum extraction is preferred to reduce the risk of anal sphincter trauma

The authors report no financial relationships relevant to this article.

CASE Large baby, extensive tear

A 28-year-old primigravida undergoes a forceps delivery with a midline episiotomy for failure to progress in the second stage of labor. At birth, the infant weighs 4 kg (8.8 lb), and the episiotomy extends to the anal verge. The resident who delivered the child is uncertain whether the anal sphincter is involved in the injury and asks a consultant to examine the perineum.

What should this examination entail?

The obstetrician is rarely culpable when a third- or fourth-degree obstetric anal sphincter injury (OASIS) occurs—but there is little excuse for letting one go undetected.

To minimize the risk of undiagnosed OASIS, a digital anorectal examination is warranted—before any suturing—in every woman who delivers vaginally. This practice can help you avoid missing isolated tears, such as “buttonhole” of the rectal mucosa, which can occur even when the anal sphincter remains intact (FIGURE 1), or a third- or fourth-degree tear that can sometimes be present behind apparently intact perineal skin (FIGURE 2).¹

Clinical training of physicians and midwives also needs to improve.

Every labor room should have a protocol for management of anal sphincter injury²; this article describes detection, diagnosis, and management, focusing on seven critical questions.

Only a physician formally trained in primary anal sphincter repair (or under supervision) should repair OASIS.

FIGURE 1 Buttonhole tear

A buttonhole tear of the rectal mucosa (arrow) with an intact external anal sphincter (EAS) demonstrated during a digital rectal examination. SOURCE: Sultan AH³ (used with permission).

FIGURE 2 Injury obscured by intact skin

(A) Intact perineum on visual examination. (B) Anal sphincter trauma detected after rectal examination. SOURCE: Sultan AH, Kettle C¹ (used with permission).

1. When (and how) should the torn perineum be examined?

The first requisite is informed consent for vaginal and rectal examination immediately after delivery. Also vital are adequate exposure of the perineum, good lighting, and, if necessary, sufficient analgesia to prevent pain-related restriction of the evaluation. It may be advisable to place the patient in the lithotomy position to improve exposure.

After visual examination of the perineum, part the labia and examine the vagina to establish the full extent of the tear. Always identify the apex of the vaginal laceration.

Next, perform a rectal examination to exclude injury to the anorectal mucosa and anal sphincter.³

Palpation is necessary to confirm OASIS

Insert the index finger into the anal canal and the thumb into the vagina and perform a pill-rolling motion to palpate the anal sphincter. If this technique is inconclusive, ask the woman to contract her anal sphincter with your fingers still in place. When the sphincter is disrupted, you feel a distinct gap anteriorly. If the perineal skin is intact, there may be an absence of puckering on the perianal skin over any underlying defect that may not be evident under regional or general anesthesia.

Because the external anal sphincter (EAS) is in a state of tonic contraction, the sphincter ends will retract when it is disrupted. These ends need to be grasped and retrieved at the time of repair.

Also identify the internal anal sphincter (IAS). It is a circular smooth muscle (FIGURE 3) that is paler in appearance (similar to the flesh of raw fish) than the striated EAS (similar to raw red meat).⁴ Under normal circumstances, the distal end of the IAS lies a few millimeters proximal to the distal end of the EAS (FIGURE 4). However, if the EAS is relaxed due to regional or general anesthesia, the distal end of the IAS will appear to be at a lower level. If the IAS or anal epithelium is torn, the EAS is, invariably, torn, too.