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Obstetric anal sphincter injury: 7 critical questions about care

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

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.

General or regional (spinal, epidural, caudal) anesthesia provides analgesia and muscle relaxation and enables proper evaluation of the full extent of the injury.

FIGURE 3 Grade 3b tear

Grade 3b tear with an intact internal anal sphincter (IAS). The external sphincter (EAS) is being grasped with Allis forceps. Note the difference in appearance of the paler IAS and darker EAS. SOURCE: Sultan AH, Kettle C¹ (used with permission).

FIGURE 4 Classification of anal sphincter injury

First- and second-degree injuries are described below.

2. Is endoanal US helpful to detect OASIS?

Endoanal ultrasonography (US) to identify OASIS requires specific expertise, particularly in the immediate postpartum period, when the anal canal is lax (especially after an epidural). Ultimately, however, the diagnosis rests on clinical assessment and a rectal examination because, even if a defect is seen on US, it has to be clinically apparent to be repaired.

In a study by Faltin and colleagues, in which routine postpartum endoanal US was used as the gold standard for diagnosis of OASIS, five of 21 women had unnecessary intervention because the sonographic defect was not clinically visible despite exploration of the anal sphincter.⁵ As a result of this unnecessary exploration based on endoanal US, 20% of these women developed severe fecal incontinence. Therefore, we believe that OASIS is best detected clinically immediately after delivery, provided the physician performs a careful examination with palpation of the anal sphincter.⁶ In such a scenario, endoanal US is of limited value.

3. How is obstetric anal sphincter trauma classified?

To standardize the classification of perineal trauma, Sultan proposed the following system, which has been adopted by the Royal College of Obstetricians and Gynaecologists and internationally^7-9:

First degree: Laceration of the vaginal epithelium or perineal skin only

Second degree: Involvement of the perineal muscles, but not the anal sphincter

Third degree: Disruption of the anal sphincter muscles (FIGURE 4):

3a: Less than 50% thickness of the external sphincter is torn
3b: More than 50% thickness of the external sphincter is torn
3c: Internal sphincter is also torn

Fourth degree: A third-degree anal tear with disruption of the anal epithelium (FIGURE 4).

If there is any ambiguity about grading of the injury, the higher grade should be selected. For example, if there is uncertainty between grades 3a and 3b, the injury should be classified as Grade 3b.

4. Is an operating room necessary?

OASIS should be repaired in the operating theater, where there is access to good lighting, appropriate equipment, and aseptic conditions. In our unit, we have a specially prepared instrument tray containing:

a Weislander self-retaining retractor
4 Allis tissue forceps
McIndoe scissors
tooth forceps
4 artery forceps
stitch scissors
a needle holder.

In addition, deep retractors (e.g., Deavers) are useful when there are associated paravaginal tears.

5. What surgical technique is recommended?

Buttonhole injury

This type of injury can occur in the rectum without disrupting the anal sphincter or perineum. It is best repaired transvaginally using interrupted Vicryl (polyglactin) sutures.

To minimize the risk of persistent rectovaginal fistula, interpose a second layer of tissue between the rectum and vagina by approximating the rectovaginal fascia. A colostomy is rarely indicated unless a large tear extends above the pelvic floor or there is gross fecal contamination of the wound.

Fourth-degree tear

Repair torn anal epithelium with interrupted Vicryl 3-0 sutures, with the knots tied in the anal lumen. Proponents of this widely described technique argue that it reduces the quantity of foreign body (knots) within the tissue and lowers the risk of infection. Concern about a foreign body probably applies to the use of catgut, which dissolves by proteolysis, rather than to newer synthetic material such as Vicryl or Dexon (polyglycolic acid), which dissolves by hydrolysis.

Subcuticular repair of anal epithelium using a transvaginal approach has also been described and could be equally effective if the terminal knots are secure.¹⁰

Sphincter muscles

Repair these muscles using 3-0 polydioxanone (PDS) dyed sutures. Compared with braided sutures, monofilament sutures are believed to lessen the risk of infection, although a randomized controlled trial revealed no difference in suture-related morbidity between Vicryl and PDS at 6 weeks postpartum.¹¹ Complete absorption of PDS takes longer than with Vicryl, with 50% tensile strength lasting more than 3 months, compared with 3 weeks for Vicryl.¹¹ To minimize suture migration, cut suture ends short and ensure that they are covered by the overlying superficial perineal muscles.

Internal anal sphincter. Repair the IAS separately from the EAS. Grasp the ends of the torn muscle using Allis forceps and perform an end-to-end repair with interrupted or mattress 3-0 PDS sutures (FIGURE 5). Overlapping repair can be technically difficult.