Have I missed a third degree tear?

Abdul Sultan, Consultant Obstetrician and Gynaecologist, Mayday University Hospital, Croydon CR7 7YE


Prospective studies have revealed that up to 35% of primiparous women sustain trauma to the anal sphincters that are unrecognised at delivery¹. It is unclear as to whether these sonographic anal sphincter defects represent missed tears or true “occult” defects. Groom and Patterson² conducted a study in which they demonstrated that the rate of third degree tears rose to 15% when all “2nd degree tears” were examined by a second person confirming that at least some tears are missed. This reflects inadequate training, and was highlighted by Sultan et al³ who reported that 91% of doctors who had had at least 6 months of training in obstetrics, and 60% of midwives, had inadequate training in perineal anatomy, while 84% and 61% respectively reported inadequate training in identifying 3rd degree tears. Another possible reason for under-diagnosis is that tears of the anal sphincter have been wrongly classified and therefore anal sphincter tears have been under-reported. Forty-one percent of trainee doctors³, 16% of midwives³ and 33% of consultants (4) classify a torn anal sphincter as a 2nd degree tear. If a third degree tear is incorrectly classified as second degree, then inappropriate repair could result in sub-optimal outcome. Sultan (5) has therefore proposed the following classification incorporated in the RCOG green top guidelines:

First degree: laceration of the vaginal epithelium or perineal skin only.

Second degree: involvement of the vaginal epithelium, perineal skin, perineal muscles and fascia but not the anal sphincter.

Third degree: disruption of the vaginal epithelium, perineal skin, perineal body and anal sphincter muscles. This should be further subdivided into: 3a: partial tear of the external sphincter involving less than 50% thickness. 3b: complete tear of the external sphincter. 3c: internal sphincter torn as well.

Fourth degree: a third degree tear with disruption of the anal epithelium.

The prevalence of anal incontinence following immediate repair of acute obstetric anal sphincter rupture ranges between 15 to 59% (6). These symptoms have a major impact on a woman's quality of life. The high prevalence may reflect sub-optimal surgical technique and post-operative management. It is time for a critical re-appraisal of these issues in order to minimise morbidity by standardising classification and management of perineal tears (6).

References

1. Sultan AH, Kamm MA, Hudson CN, Thomas JM, Bartram CI. Anal sphincter disruption during vaginal delivery. N Engl J Med 1993;329:1905-11.
2. Groom KM, Paterson-Brown S. Can we improve on the diagnosis of third degree tears? Europ J Obstet Gynecol Rep Biol 2002;101:19-21
3. Sultan AH, Kamm MA, Hudson CN. Obstetric perineal tears: an audit of training. J Obstet Gynaecol 1995;15:19-23.
4. 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 Services Research 2002,2:9
5. Sultan AH. Editorial: Obstetric perineal injury and anal incontinence. Clinical Risk 1999;5 (5):193-6.
6. Sultan AH, Thakar R. Lower genital tract and anal sphincter trauma. Best Practice & Research 2002;16(1):99-116