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Anal sphincter defects and bowel symptoms in women with and without recognized anal sphincter trauma
American Journal of Obstetrics and Gynecology (2006) 194, 1450–4
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Anal sphincter defects and bowel symptoms in women with and without recognized anal sphincter trauma Catherine M. Nichols, MD,a Marie Nam, MD, MPH,a Viswanathan Ramakrishnan, PhD,b Elizabeth H. Lamb, RNC, NP,a Nancy Currie, RNCa Departments of Obstetrics and Gynecologya and Biostatistics,b Medical College of Virginia, Virginia Commonwealth University Medical Center, Richmond, VA Received for publication June 24, 2005; revised November 7, 2005; accepted January 13, 2006
KEY WORDS Perineal laceration Anal sphincter injury Anal incontinence Endoanal ultrasonography Bowel symptoms
Objective: The purpose of this study was to determine the rate of new bowel symptoms and anal sphincter defects in primiparous women with and without recognized anal sphincter (AS) injury. Study design: One hundred seventeen primiparous women classified with increasing degrees of perineal trauma and 21 controls delivered by cesarean section were enrolled immediately postpartum and demographic and delivery data were collected. At 6 weeks’ postpartum, subjects completed a bowel function questionnaire and endoanal ultrasonography was performed. Logistic regression, chi-square, and 2-sample t tests were used for statistical analysis. Results: A significant difference in new bowel symptoms was reported in women with (39%) and without (11%) recognized AS injury (P = .002). AS defects were present in 0%, 15%, 23%, 37%, and 67% of women with C/S, first-, second-, third-, and fourth-degree lacerations, respectively. Combined defects of the internal and external AS were associated with the greatest risk of new bowel symptoms (OR 32.1 [95% CI 9.6-107], P ! .001). Conclusion: In women with and without recognized AS trauma, new bowel symptoms were strongly correlated with the presence of anatomic AS defects postpartum. Ó 2006 Mosby, Inc. All rights reserved.
Anal continence is a complex function that requires anatomic integrity of the internal and external anal sphincter along with intact sensation and motor innervation.1,2 Damage to the anal sphincter during vaginal childbirth is a major cause of fecal incontinence and likely contributes to the higher observed rates of fecal incontinence in women than in men.1,3 Approximately 35% of primiparous women sustain a perineal laceration at the time of vaginal childbirth.4 Presented at the Twenty-Sixth Annual Meeting of the American Urogynecologic Society, Atlanta, GA, September 15-17, 2005. Reprints not available from the authors. 0002-9378/$ - see front matter Ó 2006 Mosby, Inc. All rights reserved. doi:10.1016/j.ajog.2006.01.059
The reported incidence of clinically recognized thirdand fourth-degree lacerations occurs in 0.6%5 to 20%6 of vaginal deliveries, with higher rates reported with operative vaginal delivery. With the advent of endoanal ultasonography, however, as many as 35% of primiparous women and 44% of multiparous women have been identified with ‘‘occult’’ anal sphincter disruption postpartum.7,8 These endosonographic defects correlated with rates of anal incontinence or fecal urgency in 13% and 23%, respectively.7 The objectives of our study were to prospectively evaluate a cohort of primiparous women who were classified, at delivery, with increasing degrees of perineal
Nichols et al injury and compare the rates of new bowel symptoms and evidence of anatomic anal sphincter disruption in each laceration group compared with a group of control subjects delivered by cesarean section. We sought to determine how often women without recognized anal sphincter disruption (first-degree or second-degree tears) actually exhibited evidence of anal sphincter injury. We also wished to determine if a correlation existed between new bowel symptoms and anal sphincter defects on endoanal ultrasonography. This is an extension of a previously published study that evaluated differences in outcomes of women who were classified with a thirdversus a fourth-degree laceration.9
Material and methods This prospective study was performed at Virginia Commonwealth University Medical Center in Richmond, Virginia between April 1, 2003 and December 2004, after approval by the Institutional Review Board. Primiparous women who delivered a term singleton by cesarean section (controls) or vaginal birth (cases) during the study period were approached on the postpartum unit and written consent was obtained for enrollment in the study. Cases were recruited according to the degree of perineal laceration that was sustained: first-degree (vaginal epithelial tear only), second-degree (involvement of vaginal muscularis), third-degree (partial or complete anal sphincter tear), and fourth-degree (extension into the bowel lumen). The power analysis for our primary outcome measure, anal sphincter defects on endoanal ultrasonography, was based on a projected rate of 20% unrecognized anal sphincter defects in the first- and second-degree group (no recognized injury), and 50% rate of persistent anal sphincter defects in the third- and fourth-degree groups (recognized injury). In order to reach a power of 0.8 with an alpha of .05, we needed to recruit a total of 45 subjects in each group. We included a control group of women delivered by cesarean section to estimate the effect of term pregnancy on anal sphincter morphology visualized on endoanal ultrasonography. We had hoped to include 45 women in this group as well, but our enrollment goal was not met. A secondary analysis of bowel symptoms in each group was then performed. Exclusion criteria included a history of irritable bowel syndrome as defined by the Rome II Criteria,10 inflammatory bowel disease, demyelinating neurologic disease, previous anorectal anomalies or surgery, refused to undergo endoanal ultrasonography, age less than 18, and preterm delivery. Before hospital discharge from the postpartum unit, all enrolled subjects completed a Modified Manchester Bowel Function Questionnaire11 to estimate their predelivery bowel habits and symptoms. This questionnaire assesses both anal incontinence symptoms and fecal urgency, a common complaint among women with anal sphincter injury.1,12 Fecal urgency was defined as the
1451 inability to defer defecation for more than 5 minutes. Demographic and intrapartum data were collected and recorded on data sheets by a study nurse. At 6 to 8 weeks’ postpartum, subjects returned for a follow-up visit and completed a second Modified Manchester Bowel Function Questionnaire11 to assess for any changes in bowel habits since delivery. The specific domains that were extracted from the questionnaire for this study were questions regarding fecal urgency and anal incontinence. Subjects who reported incontinence of gas, liquid, or solid stool were collectively analyzed as ‘‘anal incontinence.’’ Subjects who reported new fecal urgency and/or anal incontinence were collectively analyzed as having ‘‘bowel symptoms.’’ Endoanal ultrasonography was performed in the left lateral decubitus position using a rotating rectal probe, a 7-MHz transducer (focal range 2 to 4.5 cm) and a hard, sonolucent plastic cone (Bruel and Kjaer, Naerum, Denmark). Serial images of the upper, middle, and lower anal canal were printed on paper. The integrity of the internal and external anal sphincters was evaluated separately and were reported as intact or disrupted. The endosonographic interpretation of the appearance of muscle layers has been previously validated13: an external sphincter defects appears as a break in the normal texture of the muscle ring,14 and an internal sphincter defect as a gap in the hypoechoic ring.15 For analysis, subjects were then classified into 4 groups: no internal or external sphincter defects, external sphincter defect only, internal sphincter defect only, or combined internal and external sphincter defects. The author (CMN) interpreted the ultrasound results and was blinded to the degree of laceration sustained and the results of the questionnaire until all subjects had been examined and the ultrasound results were recorded on data sheets. Statistical analyses were performed using SAS version 9.1. (SAS Language and Procedures, SAS Institute, Cary, NC). Summary statistics for continuous data are reported as mean G standard deviation (SD) and for categorical data as frequencies. Univariate statistical comparisons between the dichotomized tear-degree groups for continuous variables were performed using the 2-sample t tests and for categorical variables they were performed using Fisher exact test or chi-square tests. When appropriate, odds ratios (OR) with 95% CI are reported. Multivariate logistic regression models were used to assess the independent association of demographic variables with bowel symptoms. A P value of ! .05 was considered significant.
Results A total of 138 primiparous women completed the study: 117 cases who delivered vaginally, and 21 controls who were delivered by cesarean section. A comparison of demographic data between cases and controls is
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Nichols et al
Table I A comparison of demographic data between cases (delivered vaginally) and controls (delivered by cesarean section)
Age* Race White Black Hispanic Asian BMI* Birth weight*
Controls (n = 21) n (%)
Cases (n = 117) n (%)
25 G 6.0
24 G 5.3
8 (38) 11 (52) 0 (0) 2 (10) 35 G 8.0 3598 G 333
41 (35) 55 (47) 16 (14) 2 (2) 28.0 G 6.7 3306 G 484
Table II Demographic and delivery data in women with recognized AS injury (classified as a third or fourth degree) and without recognized AS injury (classified as a first- or second degree)
P value .67 .19
! .0001 .009
* Mean G standard deviation (SD).
presented in Table I. Women who were delivered by cesarean section had a significantly higher body mass index (BMI) and mean infant birth weight than women who delivered vaginally. The number of cases classified with a first-, second-, third-, or fourth-degree tear was 27, 26, 46, and 18, respectively. Thus, there were a total of 53 women without, and 64 women with, recognized anal sphincter injury. Table II presents a detailed comparison of demographic and delivery data between women with and without recognized anal sphincter tears. Subjects who were classified with a third- or fourth-degree tear were significantly older, had lower body mass indexes, and higher mean infant birth weights, rates of episiotomy, and operative vaginal delivery than women who were classified with first- and second-degree tears. The racial distribution also differed in that significantly more Hispanic women were present in the sphincter injury group. Postpartum, new bowel symptoms were reported by 1/21 (4.8%) of control subjects, 6/53 (11.3%) of subjects with first- or second-degree lacerations, and 25/64 (39.1%) with third- or fourth-degree tears. Women with recognized anal sphincter tears were significantly more likely to report new bowel symptoms than women without recognized anal sphincter injury (P = .007) or those delivered by cesarean section (P = .003). There was insufficient power to determine if a significant difference in bowel symptoms existed in the control group versus those classified with a first- or second-degree tear. Postpartum, the presence of any anal sphincter defect on endoanal ultrasonography in women classified as having a first-, second-, third-, or fourth-degree tear was 15%, 23%, 37%, and 67%, respectively. No anatomic defects were noted in the cesarean delivery group. Table III presents a comparison of the results of the internal and external anal sphincter integrity in women with increasing degrees of perineal injury. Overall, 10/53 (19%) classified with a first- or second-degree tear had
Age* BMI* Birth weight* Episiotomy Mode of delivery NSVD Forceps Vacuum Both Persistent OP Racey White Black Hispanic Asian Other
No recognized injury (n = 53) n (%)
Recognized injury (n = 64) n (%)
22 G 4.8 30 G 6.6 3159 G 462 10 (21)
25 G 5.3 26 G 6.3 3433 G 469 33 (52)
48 5 1 0 8
(89) (9) (2) (0) (15)
30 19 12 3 10
(47) (30) (19) (5) (16)
18 32 1 1 1
(34) (60) (2) (2) (2)
23 22 15 3 0
(36) (34) (23) (5) (0)
P value .001 .003 .002 ! .001 ! .001
.97 .03
* Mean G standard deviation (SD). y Data missing from 1 subject with recognized injury.
an anal sphincter defect. Of these, 2 involved the internal anal sphincter (IAS) only, 6 the external anal sphincter (EAS) only, and 2 were combined defects of the IAS and EAS. A significant association existed between bowel symptoms and evidence of anatomic anal sphincter disruption on endoanal ultrasound. The odds ratios for bowel symptoms in women with anal sphincter defects compared with an intact anal sphincter complex was 3.2 (95% CI 2.1-4.7) for EAS defects only, 10.1 (95% CI 4.5-22.6) for IAS defects only, and 32.1 (95% CI 9.6-107) for combined defects of the IAS C EAS (Figure). A trend did exist for higher rates of bowel symptoms in women with IAS defects only versus EAS defects only, but because of insufficient power, this was not statistically significant. In a multivariate logistic regression model for new bowel symptoms and anal sphincter defects postpartum that controlled for age, body mass index, birth weight, episiotomy, mode of delivery, and race, only persistent defects were associated with new onset of bowel symptoms. When controlling for persistent defects, the degree of perineal laceration that was assigned at time of delivery was not independently associated with bowel symptoms.
Comment Obstetric anal sphincter lacerations are known risk factors for the development of anal incontinence in women,5,16,17 a devastating condition that can have
Nichols et al Table III
1453
Persistent defects by degree of laceration
Intact IAS defect only EAS defect only Combined defect
First degree (n = 27) n (%)
Second degree (n = 26) n (%)
Third degree (n = 46) n (%)
23 1 1 2
20 1 5 0
29 1 12 4
(85) (4) (4) (7)
(77) (4) (19) (0)
Figure Odds ratios for bowel symptoms in women with anal sphincter defects compared with an intact anal sphincter complex was 3.2 (95% CI 2.1-4.7) for external anal sphincter defects only, 10.1 (95% CI 4.5-22.6) for internal sphincter defects only, and 32.1 (95% CI 9.6-107) for combined defects of the internal and external anal sphincters, P ! .001.
profoundly negative impact on quality of life. In this prospective study, women who delivered vaginally were significantly more likely to report an alteration in bowel habits than those delivered by cesarean section, most likely because of anatomic anal sphincter trauma. The presence of bowel symptoms was significantly associated with the presence of anal sphincter defects, regardless of the degree of perineal laceration that was assigned at delivery. Compared with an intact anal sphincter complex, women with isolated defects of the external anal sphincter were 3 times as likely, and those with isolated defects of the internal anal sphincter were 10 times as likely to report bowel symptoms. An approximate 30-fold increase in risk, however, was found in women with persistent combined defects of the internal and external anal sphincters. This finding confirms the results of previous studies that showed a significant association between postpartum anorectal dysfunction and anatomic anal sphincter injury.5,8,18-20 The importance of accurately identifying and repairing defects of the internal and external anal sphincters at delivery is clear from this study. Previous investigators have reported that approximately one third of primiparous women7,8,21 sustain ‘‘occult’’ or unrecognized anal sphincter trauma during delivery. In this study, 19% of
(63) (2) (26) (9)
Fourth degree (n = 18) n (%) 6 1 2 9
(33) (6) (11) (50)
C/S (n = 21) n (%) 21 0 0 0
(100) (0) (0) (0)
women who were classified as having a first- or seconddegree tear were actually found to have evidence of anal sphincter injury postpartum. Were all these defects truly ‘‘occult’’ or could they have been detected by an independent assessor with additional focused training in this area? Two previous studies22,23 have demonstrated dramatic improvements in detection rates of anal sphincter lacerations when a trained clinician assesses the tear. In our obstetrics unit, we typically rely on lower-level residents to determine the degree of laceration that is present, even though they may not be adequately educated in this area. An audit of training regarding obstetric perineal trauma in the United Kingdom found that general education in perineal trauma was poor, and most respondents felt inadequately prepared to correctly identify and repair anal sphincter lacerations.24 Similar problems with education regarding perineal injury exist in the United States. A survey of fourth-year ob/gyn residents found that almost 60% reportedly received no didactic training on episiotomy repair techniques or formal teaching on pelvic floor anatomy.25 Given that the consequences of misclassifying a tear are potentially deleterious to future anal continence, efforts towards adequate supervision and education in this area are urgently needed. An interesting observation was made regarding the demographic differences between women with and without recognized anal sphincter injury. Women who were classified with a third- or fourth-degree tear were older, had a lower mean BMI, and were more likely to be Hispanic than women classified with a first- or seconddegree tear. Several other studies have reported a correlation between age and sphincter injury, the etiology of which is unclear.26-28 A previous study also reported an association between short stature and anal sphincter injury, but not necessarily a lower BMI.29 It is possible that in thinner women it is simply easier to recognize anal sphincter defects. As reported in numerous other studies,30-32 we found a significant association between operative vaginal delivery, midline episiotomy, and higher mean infant birth weight with recognized anal sphincter injury. In conclusion, this study demonstrates a clear association between persistent anal sphincter defects and bowel symptoms, regardless of the initial degree of tear that was assigned at delivery. Approximately 1 out of 5
1454 women who were classified with a first- or second-degree tear actually demonstrated evidence of anal sphincter injury postpartum. We show a trend towards the relative importance of the external and internal anal sphincters in the maintenance of anal continence, but clearly exhibit the dramatic increase in risk of bowel symptoms with combined persistent defects of the internal and external sphincters. We strongly support efforts to improve focused training in the identification and repair of anal sphincter lacerations.
References 1. Madoff RD, Williams JG, Caushaj PF. Fecal incontinence. N Engl J Med 1992;326:1002-7. 2. Toglia MR, DeLancey JO. Anal incontinence and the obstetriciangynecologist. Obstet Gynecol 1994;84:731-40. 3. Kamm MA. Obstetric damage and faecal incontinence. Lancet 1994;344:730-3. 4. Mayerhofer K, Bodner-Adler B, Bodner K, Rabl M, Kaider A, Wagenbichler P, et al. Traditional care of the perineum during birth. A prospective, randomized, multicenter study of 1,076 women. J Reprod Med 2002;47:477-82. 5. Sultan AH, Kamm MA, Hudson CN, Bartram CI. Third degree obstetric anal sphincter tears: risk factors and outcome of primary repair. BMJ 1994;308:887-91. 6. Crawford LA, Quint EH, Pearl ML, DeLancey JO. Incontinence following rupture of the anal sphincter during delivery. Obstet Gynecol 1993;82:527-31. 7. Sultan AH, Kamm MA, Hudson CN, Thomas JM, Bartram CI. Anal-sphincter disruption during vaginal delivery. N Engl J Med 1993;329:1905-11. 8. Donnelly V, Fynes M, Campbell D, Johnson H, O’Connell PR, O’Herlihy C. Obstetric events leading to anal sphincter damage. Obstet Gynecol 1998;92:955-61. 9. Nichols C, Lamb E, Ramakrishnan R. Differences in outcomes after third- versus fourth-degree perineal laceration repair: a prospective study. Am J Obstet Gynecol 2005;193:530-6. 10. Boyce PM, Koloski NA, Talley NJ. Irritable bowel syndrome according to varying diagnostic criteria: are the new Rome II criteria unnecessarily restrictive for research and practice? Am J Gastroenterol 2000;95:3176-83. 11. Kwon S, Visco AG, Fitzgerald MP, Ye W, Whitehead WE. Validity and reliability of the Modified Manchester Health Questionnaire in assessing patients with fecal incontinence. Dis Colon Rectum 2005;48:323-31; discussion 331-4. 12. Tetzschner T, Sorensen M, Lose G, Christiansen J. Anal and urinary incontinence in women with obstetric anal sphincter rupture. BJOG 1996;103:1034-40. 13. Sultan AH, Kamm MA, Hudson CN, Nicholls JR, Bartram CI. Endosonography of the anal sphincters: normal anatomy and comparison with manometry. Clin Radiol 1994;49:368-74. 14. Sultan AH, Kamm MA, Talbot IC, Nicholls RJ, Bartram CI. Anal endosonography for identifying external sphincter defects confirmed histologically. Br J Surg 1994;81:463-5.
Nichols et al 15. Sultan AH, Kamm MA, Nicholls RJ, Bartram CI. Prospective study of the extent of internal anal sphincter division during lateral sphincterotomy. Dis Colon Rectum 1994;37:1031-3. 16. Zetterstrom J, Lopez A, Anzen B, Norman M, Holmstrom B, Mellgren A. Anal sphincter tears at vaginal delivery: risk factors and clinical outcome of primary repair. Obstet Gynecol 1999;94: 21-8. 17. Zetterstrom JP, Lopez A, Anzen B, Dolk A, Norman M, Mellgren A. Anal incontinence after vaginal delivery: a prospective study in primiparous women. BJOG 1999;106:324-30. 18. Pinta TM, Kylanpaa ML, Salmi TK, Teramo KA, Luukkonen PS. Primary sphincter repair: are the results of the operation good enough? Dis Colon Rectum 2004;47:18-23. 19. Poen AC, Felt-Bersma RJ, Strijers RL, Dekker GA, Cuesta MA, Meuwissen SG. Third-degree obstetric perineal tear: long-term clinical and functional results after primary repair. Br J Surg 1998;85:1433-8. 20. Abramowitz L, Sobhani I, Ganansia R, Vuagnat A, Benifla JL, Darai E, et al. Are sphincter defects the cause of anal incontinence after vaginal delivery? Results of a prospective study. Dis Colon Rectum 2000;43:590-6; discussion 596-8. 21. Chaliha C, Sultan AH, Bland JM, Monga AK, Stanton SL. Anal function: effect of pregnancy and delivery. Am J Obstet Gynecol 2001;185:427-32. 22. Groom KM, Paterson-Brown S. Can we improve on the diagnosis of third degree tears? Eur J Obstet Gynecol Reprod Biol 2002;101: 19-21. 23. Andrews V. Occult anal sphincter injuriesdmyth or reality? Neurourol Urodyn 2004;23:442-4. 24. 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. 25. McLennan MT, Melick CF, Clancy SL, Artal R. Episiotomy and perineal repair. An evaluation of resident education and experience. J Reprod Med 2002;47:1025-30. 26. Angioli R, Gomez-Marin O, Cantuaria G, O’Sullivan MJ. Severe perineal lacerations during vaginal delivery: the University of Miami experience. Am J Obstet Gynecol 2000;182:1083-5. 27. Walfisch A, Hallak M, Harlev S, Mazor M, Shoham-Vardi I. Association of spontaneous perineal stretching during delivery with perineal lacerations. J Reprod Med 2005;50:23-8. 28. MacArthur C, Glazener CM, Wilson PD, Herbison GP, Gee H, Lang GD, et al. Obstetric practice and faecal incontinence three months after delivery. BJOG 2001;108:678-83. 29. Gudmundsson S, Henningsson AC, Lindqvist P. Correlation of birth injury with maternal height and birthweight. BJOG 2005; 112:764-7. 30. Christianson LM, Bovbjerg VE, McDavitt EC, Hullfish KL. Risk factors for perineal injury during delivery. Am J Obstet Gynecol 2003;189:255-60. 31. Hudelist G, Gelle’n J, Singer C, Ruecklinger E, Czerwenka K, Kandolf O, et al. Factors predicting severe perineal trauma during childbirth: role of forceps delivery routinely combined with mediolateral episiotomy. Am J Obstet Gynecol 2005;192: 875-81. 32. Dandolu V, Chatwani A, Harmanli O, Floro C, Gaughan JP, Hernandez E. Risk factors for obstetrical anal sphincter lacerations. Int Urogynecol J Pelvic Floor Dysfunct 2005;16:304-7.
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Anal sphincter defects and bowel symptoms in women with and without recognized anal sphincter trauma Catherine M. Nichols, MD,a Marie Nam, MD, MPH,a Viswanathan Ramakrishnan, PhD,b Elizabeth H. Lamb, RNC, NP,a Nancy Currie, RNCa Departments of Obstetrics and Gynecologya and Biostatistics,b Medical College of Virginia, Virginia Commonwealth University Medical Center, Richmond, VA Received for publication June 24, 2005; revised November 7, 2005; accepted January 13, 2006
KEY WORDS Perineal laceration Anal sphincter injury Anal incontinence Endoanal ultrasonography Bowel symptoms
Objective: The purpose of this study was to determine the rate of new bowel symptoms and anal sphincter defects in primiparous women with and without recognized anal sphincter (AS) injury. Study design: One hundred seventeen primiparous women classified with increasing degrees of perineal trauma and 21 controls delivered by cesarean section were enrolled immediately postpartum and demographic and delivery data were collected. At 6 weeks’ postpartum, subjects completed a bowel function questionnaire and endoanal ultrasonography was performed. Logistic regression, chi-square, and 2-sample t tests were used for statistical analysis. Results: A significant difference in new bowel symptoms was reported in women with (39%) and without (11%) recognized AS injury (P = .002). AS defects were present in 0%, 15%, 23%, 37%, and 67% of women with C/S, first-, second-, third-, and fourth-degree lacerations, respectively. Combined defects of the internal and external AS were associated with the greatest risk of new bowel symptoms (OR 32.1 [95% CI 9.6-107], P ! .001). Conclusion: In women with and without recognized AS trauma, new bowel symptoms were strongly correlated with the presence of anatomic AS defects postpartum. Ó 2006 Mosby, Inc. All rights reserved.
Anal continence is a complex function that requires anatomic integrity of the internal and external anal sphincter along with intact sensation and motor innervation.1,2 Damage to the anal sphincter during vaginal childbirth is a major cause of fecal incontinence and likely contributes to the higher observed rates of fecal incontinence in women than in men.1,3 Approximately 35% of primiparous women sustain a perineal laceration at the time of vaginal childbirth.4 Presented at the Twenty-Sixth Annual Meeting of the American Urogynecologic Society, Atlanta, GA, September 15-17, 2005. Reprints not available from the authors. 0002-9378/$ - see front matter Ó 2006 Mosby, Inc. All rights reserved. doi:10.1016/j.ajog.2006.01.059
The reported incidence of clinically recognized thirdand fourth-degree lacerations occurs in 0.6%5 to 20%6 of vaginal deliveries, with higher rates reported with operative vaginal delivery. With the advent of endoanal ultasonography, however, as many as 35% of primiparous women and 44% of multiparous women have been identified with ‘‘occult’’ anal sphincter disruption postpartum.7,8 These endosonographic defects correlated with rates of anal incontinence or fecal urgency in 13% and 23%, respectively.7 The objectives of our study were to prospectively evaluate a cohort of primiparous women who were classified, at delivery, with increasing degrees of perineal
Nichols et al injury and compare the rates of new bowel symptoms and evidence of anatomic anal sphincter disruption in each laceration group compared with a group of control subjects delivered by cesarean section. We sought to determine how often women without recognized anal sphincter disruption (first-degree or second-degree tears) actually exhibited evidence of anal sphincter injury. We also wished to determine if a correlation existed between new bowel symptoms and anal sphincter defects on endoanal ultrasonography. This is an extension of a previously published study that evaluated differences in outcomes of women who were classified with a thirdversus a fourth-degree laceration.9
Material and methods This prospective study was performed at Virginia Commonwealth University Medical Center in Richmond, Virginia between April 1, 2003 and December 2004, after approval by the Institutional Review Board. Primiparous women who delivered a term singleton by cesarean section (controls) or vaginal birth (cases) during the study period were approached on the postpartum unit and written consent was obtained for enrollment in the study. Cases were recruited according to the degree of perineal laceration that was sustained: first-degree (vaginal epithelial tear only), second-degree (involvement of vaginal muscularis), third-degree (partial or complete anal sphincter tear), and fourth-degree (extension into the bowel lumen). The power analysis for our primary outcome measure, anal sphincter defects on endoanal ultrasonography, was based on a projected rate of 20% unrecognized anal sphincter defects in the first- and second-degree group (no recognized injury), and 50% rate of persistent anal sphincter defects in the third- and fourth-degree groups (recognized injury). In order to reach a power of 0.8 with an alpha of .05, we needed to recruit a total of 45 subjects in each group. We included a control group of women delivered by cesarean section to estimate the effect of term pregnancy on anal sphincter morphology visualized on endoanal ultrasonography. We had hoped to include 45 women in this group as well, but our enrollment goal was not met. A secondary analysis of bowel symptoms in each group was then performed. Exclusion criteria included a history of irritable bowel syndrome as defined by the Rome II Criteria,10 inflammatory bowel disease, demyelinating neurologic disease, previous anorectal anomalies or surgery, refused to undergo endoanal ultrasonography, age less than 18, and preterm delivery. Before hospital discharge from the postpartum unit, all enrolled subjects completed a Modified Manchester Bowel Function Questionnaire11 to estimate their predelivery bowel habits and symptoms. This questionnaire assesses both anal incontinence symptoms and fecal urgency, a common complaint among women with anal sphincter injury.1,12 Fecal urgency was defined as the
1451 inability to defer defecation for more than 5 minutes. Demographic and intrapartum data were collected and recorded on data sheets by a study nurse. At 6 to 8 weeks’ postpartum, subjects returned for a follow-up visit and completed a second Modified Manchester Bowel Function Questionnaire11 to assess for any changes in bowel habits since delivery. The specific domains that were extracted from the questionnaire for this study were questions regarding fecal urgency and anal incontinence. Subjects who reported incontinence of gas, liquid, or solid stool were collectively analyzed as ‘‘anal incontinence.’’ Subjects who reported new fecal urgency and/or anal incontinence were collectively analyzed as having ‘‘bowel symptoms.’’ Endoanal ultrasonography was performed in the left lateral decubitus position using a rotating rectal probe, a 7-MHz transducer (focal range 2 to 4.5 cm) and a hard, sonolucent plastic cone (Bruel and Kjaer, Naerum, Denmark). Serial images of the upper, middle, and lower anal canal were printed on paper. The integrity of the internal and external anal sphincters was evaluated separately and were reported as intact or disrupted. The endosonographic interpretation of the appearance of muscle layers has been previously validated13: an external sphincter defects appears as a break in the normal texture of the muscle ring,14 and an internal sphincter defect as a gap in the hypoechoic ring.15 For analysis, subjects were then classified into 4 groups: no internal or external sphincter defects, external sphincter defect only, internal sphincter defect only, or combined internal and external sphincter defects. The author (CMN) interpreted the ultrasound results and was blinded to the degree of laceration sustained and the results of the questionnaire until all subjects had been examined and the ultrasound results were recorded on data sheets. Statistical analyses were performed using SAS version 9.1. (SAS Language and Procedures, SAS Institute, Cary, NC). Summary statistics for continuous data are reported as mean G standard deviation (SD) and for categorical data as frequencies. Univariate statistical comparisons between the dichotomized tear-degree groups for continuous variables were performed using the 2-sample t tests and for categorical variables they were performed using Fisher exact test or chi-square tests. When appropriate, odds ratios (OR) with 95% CI are reported. Multivariate logistic regression models were used to assess the independent association of demographic variables with bowel symptoms. A P value of ! .05 was considered significant.
Results A total of 138 primiparous women completed the study: 117 cases who delivered vaginally, and 21 controls who were delivered by cesarean section. A comparison of demographic data between cases and controls is
1452
Nichols et al
Table I A comparison of demographic data between cases (delivered vaginally) and controls (delivered by cesarean section)
Age* Race White Black Hispanic Asian BMI* Birth weight*
Controls (n = 21) n (%)
Cases (n = 117) n (%)
25 G 6.0
24 G 5.3
8 (38) 11 (52) 0 (0) 2 (10) 35 G 8.0 3598 G 333
41 (35) 55 (47) 16 (14) 2 (2) 28.0 G 6.7 3306 G 484
Table II Demographic and delivery data in women with recognized AS injury (classified as a third or fourth degree) and without recognized AS injury (classified as a first- or second degree)
P value .67 .19
! .0001 .009
* Mean G standard deviation (SD).
presented in Table I. Women who were delivered by cesarean section had a significantly higher body mass index (BMI) and mean infant birth weight than women who delivered vaginally. The number of cases classified with a first-, second-, third-, or fourth-degree tear was 27, 26, 46, and 18, respectively. Thus, there were a total of 53 women without, and 64 women with, recognized anal sphincter injury. Table II presents a detailed comparison of demographic and delivery data between women with and without recognized anal sphincter tears. Subjects who were classified with a third- or fourth-degree tear were significantly older, had lower body mass indexes, and higher mean infant birth weights, rates of episiotomy, and operative vaginal delivery than women who were classified with first- and second-degree tears. The racial distribution also differed in that significantly more Hispanic women were present in the sphincter injury group. Postpartum, new bowel symptoms were reported by 1/21 (4.8%) of control subjects, 6/53 (11.3%) of subjects with first- or second-degree lacerations, and 25/64 (39.1%) with third- or fourth-degree tears. Women with recognized anal sphincter tears were significantly more likely to report new bowel symptoms than women without recognized anal sphincter injury (P = .007) or those delivered by cesarean section (P = .003). There was insufficient power to determine if a significant difference in bowel symptoms existed in the control group versus those classified with a first- or second-degree tear. Postpartum, the presence of any anal sphincter defect on endoanal ultrasonography in women classified as having a first-, second-, third-, or fourth-degree tear was 15%, 23%, 37%, and 67%, respectively. No anatomic defects were noted in the cesarean delivery group. Table III presents a comparison of the results of the internal and external anal sphincter integrity in women with increasing degrees of perineal injury. Overall, 10/53 (19%) classified with a first- or second-degree tear had
Age* BMI* Birth weight* Episiotomy Mode of delivery NSVD Forceps Vacuum Both Persistent OP Racey White Black Hispanic Asian Other
No recognized injury (n = 53) n (%)
Recognized injury (n = 64) n (%)
22 G 4.8 30 G 6.6 3159 G 462 10 (21)
25 G 5.3 26 G 6.3 3433 G 469 33 (52)
48 5 1 0 8
(89) (9) (2) (0) (15)
30 19 12 3 10
(47) (30) (19) (5) (16)
18 32 1 1 1
(34) (60) (2) (2) (2)
23 22 15 3 0
(36) (34) (23) (5) (0)
P value .001 .003 .002 ! .001 ! .001
.97 .03
* Mean G standard deviation (SD). y Data missing from 1 subject with recognized injury.
an anal sphincter defect. Of these, 2 involved the internal anal sphincter (IAS) only, 6 the external anal sphincter (EAS) only, and 2 were combined defects of the IAS and EAS. A significant association existed between bowel symptoms and evidence of anatomic anal sphincter disruption on endoanal ultrasound. The odds ratios for bowel symptoms in women with anal sphincter defects compared with an intact anal sphincter complex was 3.2 (95% CI 2.1-4.7) for EAS defects only, 10.1 (95% CI 4.5-22.6) for IAS defects only, and 32.1 (95% CI 9.6-107) for combined defects of the IAS C EAS (Figure). A trend did exist for higher rates of bowel symptoms in women with IAS defects only versus EAS defects only, but because of insufficient power, this was not statistically significant. In a multivariate logistic regression model for new bowel symptoms and anal sphincter defects postpartum that controlled for age, body mass index, birth weight, episiotomy, mode of delivery, and race, only persistent defects were associated with new onset of bowel symptoms. When controlling for persistent defects, the degree of perineal laceration that was assigned at time of delivery was not independently associated with bowel symptoms.
Comment Obstetric anal sphincter lacerations are known risk factors for the development of anal incontinence in women,5,16,17 a devastating condition that can have
Nichols et al Table III
1453
Persistent defects by degree of laceration
Intact IAS defect only EAS defect only Combined defect
First degree (n = 27) n (%)
Second degree (n = 26) n (%)
Third degree (n = 46) n (%)
23 1 1 2
20 1 5 0
29 1 12 4
(85) (4) (4) (7)
(77) (4) (19) (0)
Figure Odds ratios for bowel symptoms in women with anal sphincter defects compared with an intact anal sphincter complex was 3.2 (95% CI 2.1-4.7) for external anal sphincter defects only, 10.1 (95% CI 4.5-22.6) for internal sphincter defects only, and 32.1 (95% CI 9.6-107) for combined defects of the internal and external anal sphincters, P ! .001.
profoundly negative impact on quality of life. In this prospective study, women who delivered vaginally were significantly more likely to report an alteration in bowel habits than those delivered by cesarean section, most likely because of anatomic anal sphincter trauma. The presence of bowel symptoms was significantly associated with the presence of anal sphincter defects, regardless of the degree of perineal laceration that was assigned at delivery. Compared with an intact anal sphincter complex, women with isolated defects of the external anal sphincter were 3 times as likely, and those with isolated defects of the internal anal sphincter were 10 times as likely to report bowel symptoms. An approximate 30-fold increase in risk, however, was found in women with persistent combined defects of the internal and external anal sphincters. This finding confirms the results of previous studies that showed a significant association between postpartum anorectal dysfunction and anatomic anal sphincter injury.5,8,18-20 The importance of accurately identifying and repairing defects of the internal and external anal sphincters at delivery is clear from this study. Previous investigators have reported that approximately one third of primiparous women7,8,21 sustain ‘‘occult’’ or unrecognized anal sphincter trauma during delivery. In this study, 19% of
(63) (2) (26) (9)
Fourth degree (n = 18) n (%) 6 1 2 9
(33) (6) (11) (50)
C/S (n = 21) n (%) 21 0 0 0
(100) (0) (0) (0)
women who were classified as having a first- or seconddegree tear were actually found to have evidence of anal sphincter injury postpartum. Were all these defects truly ‘‘occult’’ or could they have been detected by an independent assessor with additional focused training in this area? Two previous studies22,23 have demonstrated dramatic improvements in detection rates of anal sphincter lacerations when a trained clinician assesses the tear. In our obstetrics unit, we typically rely on lower-level residents to determine the degree of laceration that is present, even though they may not be adequately educated in this area. An audit of training regarding obstetric perineal trauma in the United Kingdom found that general education in perineal trauma was poor, and most respondents felt inadequately prepared to correctly identify and repair anal sphincter lacerations.24 Similar problems with education regarding perineal injury exist in the United States. A survey of fourth-year ob/gyn residents found that almost 60% reportedly received no didactic training on episiotomy repair techniques or formal teaching on pelvic floor anatomy.25 Given that the consequences of misclassifying a tear are potentially deleterious to future anal continence, efforts towards adequate supervision and education in this area are urgently needed. An interesting observation was made regarding the demographic differences between women with and without recognized anal sphincter injury. Women who were classified with a third- or fourth-degree tear were older, had a lower mean BMI, and were more likely to be Hispanic than women classified with a first- or seconddegree tear. Several other studies have reported a correlation between age and sphincter injury, the etiology of which is unclear.26-28 A previous study also reported an association between short stature and anal sphincter injury, but not necessarily a lower BMI.29 It is possible that in thinner women it is simply easier to recognize anal sphincter defects. As reported in numerous other studies,30-32 we found a significant association between operative vaginal delivery, midline episiotomy, and higher mean infant birth weight with recognized anal sphincter injury. In conclusion, this study demonstrates a clear association between persistent anal sphincter defects and bowel symptoms, regardless of the initial degree of tear that was assigned at delivery. Approximately 1 out of 5
1454 women who were classified with a first- or second-degree tear actually demonstrated evidence of anal sphincter injury postpartum. We show a trend towards the relative importance of the external and internal anal sphincters in the maintenance of anal continence, but clearly exhibit the dramatic increase in risk of bowel symptoms with combined persistent defects of the internal and external sphincters. We strongly support efforts to improve focused training in the identification and repair of anal sphincter lacerations.
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