Perineal examination as a predictor of underlying external anal sphincter damage

Objective To assess the relation between perineal inspection and sphincter integrity in parous women.
Design Prospective observational study.
Setting District general hospital.
Population Fifty-seven consecutive parous women attending a gynaecology clinic for problems unrelated to the pelvic floor.
Methods A detailed history of bowel function and mode of delivery obtained; the perineum inspected to determine the presence and position of scarring, and anal endosonography performed.
Results In 19 women with an intact perineum on inspection, endosonography showed perineal scarring in five, with both perineal and sphincter scarring in three. Four had urge faecal incontinence. Three patients had a perineal tear only on inspection, but this group was too small for analysis and was discounted. Nine had an episiotomy scar only. Endosonography demonstrated perineal scarring in four, and combined perineal and sphincter scarring in two; one woman in this group had urge faecal incontinence. Twenty-six women had episiotomy and perineal tears on inspection. Endosonography revealed underlying perineal scarring in five women, with combined perineal and sphincter scarring in 14; six women in this group had urge faecal incontinence and one passive incontinence for flatus. Sonographically the scarring was anterior and circumferential rather than radial, and mostly left-sided, whereas on inspection episiotomy and perineal scarring were right sided.
Conclusions A normal perineum on clinical examination does not exclude underlying sphincter damage. The incidence of sphincter damage increases significantly when an episiotomy scar is associated with a perineal tear.     

Recovery of external anal sphincter contractile function after prolonged vaginal distention or sphincter transection in an animal model

OBJECTIVE: To estimate the effect of prolonged vaginal distention and anal sphincter transection on contractile properties of the external anal sphincter as a function of time. METHODS: One hundred thirty-nine young female virginal rats were randomly assigned into four treatment groups (sham, vaginal distention, transection of anal sphincter plus repair, or combined distention and transection plus repair). After 3 days, 3 months, or 6 months, the anal sphincter complex was analyzed for peak force of twitch tension, peak tetanic force, fatigue, and maximal responses to electrical field stimulation. Statistical analysis was performed using analysis of variance (Student-Neuman-Keuls). RESULTS: After 3 days, vaginal balloon distention, anal sphincter transection with repair, and combined distention and transection plus repair resulted in compromise of maximal tetanic contraction and electrical field stimulated force generation. Twitch tension, and resistance to fatigue were also significantly decreased in animals with anal sphincter disruption and repair with and without vaginal distention at 3 days. Contractile function of the external anal sphincter, however, was fully recovered by 3 months and was sustained at 6 months in all treatment groups. The time course of repair was slower in animals with sphincter laceration. CONCLUSION: Anal sphincter transection with or without antecedent prolonged vaginal distention results in severe compromise of external anal sphincter function in the immediate period after injury. In this animal model, complete recovery of external anal sphincter function occurs 3 months after initial insult.     

Magnetic resonance imaging and 3-dimensional analysis of external anal sphincter anatomy

OBJECTIVE: To use magnetic resonance images of living women and 3-dimensional modeling software to identify the component parts and characteristic features of the external anal sphincter (EAS) that have visible separation or varying origins and insertions. METHODS: Detailed structural analysis of anal sphincter anatomy was performed on 3 pelvic magnetic resonance imaging (MRI) data sets selected for image clarity from ongoing studies involving nulliparous women. The relationships of anal sphincter structures seen in axial, sagittal, and coronal planes were examined using the 3-D Slicer 2.1b1 software program. The following were requirements for sphincter elements to be considered separate: 1) a clear and consistently visible separation or 2) a different origin or insertion. The characteristic features identified in this way were then evaluated in images from an additional 50 nulliparas for the frequency of feature visibility. RESULTS: There were 3 components of the EAS that met criteria as being "separate" structures. The main body (EAS-M) is separated from the subcutaneous external anal sphincter (SQ-EAS) by a clear division that could be observed in all (100%) of the MRI scans reviewed. The wing-shaped end (EAS-W) has fibers that do not cross the midline ventrally, but have lateral origins near the ischiopubic ramus. This EAS-W component was visible in 76% of the nulliparas reviewed. CONCLUSION: Three distinct external anal sphincter components can be identified by MRI in the majority of nulliparous women.     

Obstetric anal sphincter lacerations

OBJECTIVE: To estimate the frequency of obstetric anal sphincter laceration and to identify characteristics associated with this complication, including modifiable risk factors. METHODS: A population-based, retrospective study of over 2 million vaginal deliveries at California hospitals was performed, using information from birth certificates and discharge summaries for 1992 through 1997. We excluded preterm births, stillbirths, breech deliveries, and multiple gestations. The main outcome measure was obstetric anal sphincter laceration (third and fourth degree). RESULTS: The frequency of anal sphincter lacerations was 5.85% (95% confidence interval [CI] 5.82, 5.88), decreasing significantly from 6.35% (95% CI 6.27, 6.43) in 1992 to 5.43% (95% CI 5.35, 5.51) in 1997 (P <.01). Using logistic regression analysis, we identified primiparity as the dominant risk factor (odds ratio [OR] for women with prior vaginal birth 0.15; 95% CI 0.14, 0.15). Birth weight over 4000 g was also highly significant (OR 2.17; 95% CI 2.07, 2.27). Lacerations occurred more often among women of certain racial and ethnic groups: Indian women (OR 2.5; 95% CI 2.23, 2.79) and Filipina women (OR 1.63; 95% CI 1.50, 1.77) were at highest risk. Episiotomy decreased the likelihood of third-degree lacerations (OR 0.81; 95% CI 0.78, 0.85), but increased the risk of fourth-degree lacerations (OR 1.12; 95% CI 1.05, 1.19). Operative delivery increased the risk of sphincter laceration, with vacuum delivery (OR 2.30; 95% CI 2.21, 2.40) presenting a greater risk than forceps delivery (OR 1.45; 95% CI 1.37, 1.52). CONCLUSION: Anal sphincter lacerations are strongly associated with primiparity, macrosomia, and operative vaginal delivery. Of the modifiable risk factors, operative vaginal delivery remains the dominant independent variable.     

Postpartum anal sphincter dysfunction

Faecal incontinence presents with a female to male ratio of 8:1 suggesting childbirth as the principal causative factor, although most women do not become symptomatic until after menopause. Obstetric injury may arise as a result of direct muscular damage to the anal sphincter, as occurs during a third-degree tear, and/or may be the result of cumulative damage to the pudendal nerves. Symptomatic women should be assessed in a dedicated clinic where time is available for comprehensive evaluation. Clinical examination alone may fail to detect specific abnormalities. The performance of anal manometry, endoanal ultrasound and neurophysiology studies of the pelvic floor will increase the diagnostic yield. Treatment may include dietary manipulation and physiotherapy. In severe cases surgery may be warranted with secondary repair of the anal sphincter muscle. Adequate primary management of third-degree tears requires careful appraisal so as to reduce the incidence of later incontinence.     

Quantitative electromyographic analysis of levator ani and external anal sphincter muscles of nulliparous women

OBJECTIVES: Our aims were to introduce a method of digital quantitative electromyography of the levator ani and external anal sphincter muscles and to establish reference values. STUDY DESIGN: Fifteen nulliparous, symptom-free women underwent concentric needle electromyographic examination of the levator ani and external anal sphincter. We sampled the levator ani transvaginally at 4 sites and the external anal sphincter at 2 sites. The signal was filtered and amplified, and digital recordings were made at 3 levels of voluntary activation at each site. Analyses of motor unit action potentials and interference patterns were performed with the use of these taped signals. Normal ranges were generated and compared with those established for other striated muscles. RESULTS: The mean age of the subjects was 28.7+/-7.5 years. A median of 24 motor unit action potentials was recorded in each levator ani, and a median of 6 was recorded in each external anal sphincter. Parameters of the levator ani action potentials were significantly greater than those of the external anal sphincter in amplitude (0.48 vs. 0.37 mV; P =.001), duration (10.40 vs. 8.27 ms; P =.002), number of turns per second (2. 80 vs. 2.28; P<.001), and area (0.65 vs. 0.36; P<.001). Parameters of the interference patterns were significantly greater in the levator ani than in the external anal sphincter in number of turns per second (241.6 vs. 183.9; P =.015), amplitude (302.7 vs. 225.3 microV; P<.0001), activity (95.6 vs 61.2; P =.004), envelope size (861.1 vs 567.6 microV; P<.0001), and number of small segments (105. 8 vs 81.4; P =.047). There were no significant differences between levator ani, external anal sphincter, and published parameters from the biceps muscle with regard to amplitude and duration of motor unit action potentials. CONCLUSIONS: Electromyography of the levator ani and external anal sphincter is feasible and well tolerated. Our findings confirm that the levator ani muscle has larger, more readily recruited motor units than does the external anal sphincter. Ranges for important quantitative electromyographic parameters for these muscles are similar to those published for the biceps.     

Risk factors for rupture of the anal sphincter

OBJECTIVE: To evaluate risk factors for rupture of the anal sphincter during vaginal delivery. MATERIAL AND METHODS: All 292 parturients with rupture of the anal sphincter in four neighbouring central hospitals in southern Sweden between 1988 and 1990 were identified retrospectively. For each case a control was selected, the sole matching criterion being that the control woman was the next to give birth vaginally in the same unit as the case. Only singleton deliveries were included. For comparison of risk factors among cases and controls, McNemar's test was used for bivariate testing; multiple regression analysis was restricted to those variables found to be significant in the bivariate analysis. Odds ratios (OR) were calculated with 95% confidence limits (CL). RESULTS: In all, 292 of 22,653 deliveries (1.3%) had a rupture of the anal sphincter. Of a total of 14 independent variables explored, 8 were found to be significantly associated with rupture of the anal sphincter in the bivariate testing. In the following multivariate analysis, three variables remained significantly associated with rupture of the anal sphincter: birthweight > or = 4000 g (OR 2.6; CL 1.7, 3.9), primiparity (OR 2.2; CL 1.5, 3.3) and episiotomy (OR 1.7; CL 1.1, 2.6). CONCLUSION: Episiotomy appears to be significantly associated with rupture of the anal sphincter. In contrast to primiparity and birthweight, the incidence of episiotomy during vaginal delivery may easily be reduced. However, only a prospective, controlled study will disclose the true negative or positive effects of episiotomy.     

Risk factors for anal sphincter tear in multiparas

OBJECTIVE: To assess maternal, newborn, and obstetric risk factors associated with anal sphincter tear in multiparous women. METHODS: This case-control study identified 18,779 multiparous vaginal deliveries from 1992 to 2004 from an obstetric automated record database at the University of Alabama at Birmingham. Two hundred eighty-four patients were selected, 145 cases and 139 controls. Variables from the index pregnancy and prior pregnancies were analyzed, and multivariable logistic regression models were constructed to determine significant predictor variables for anal sphincter tear in multiparous women. RESULTS: One hundred forty-five multiparous women with no history of cesarean delivery sustained a sphincter tear. Multivariable logistic regression showed a significant association with episiotomy (odds ratio [OR] 16.3, 95% confidence interval [CI] 7.7-34.4), shoulder dystocia (OR 7.9, CI 1.6-38), forceps delivery (OR 4.7, CI 2.0-11.2), and being married (OR 2.2, CI 1.1-4.6). A second exploratory model that included variables from previous pregnancies, showed that in addition to episiotomy (OR 34.6, CI 8.8-136), shoulder dystocia (OR 11.1, CI 1.3-95.2), forceps delivery (OR 6.1, CI 1.6-23.5), previous sphincter tear (OR 7.7, CI 1.2-48.7), and second stage of labor greater than 1 hour (OR 6.7, CI 1.1-42.5) were associated with tear. CONCLUSION: The strongest clinical risk factors for anal sphincter tear in multiparous women are episiotomy, shoulder dystocia, previous sphincter tear, prolonged second stage of labor, and forceps delivery. LEVEL OF EVIDENCE: II-2.     

Risk of recurrence of anal sphincter lacerations

OBJECTIVE: To estimate the rate of recurrence of anal sphincter lacerations in subsequent pregnancies and analyze the risk factors associated with recurrent lacerations METHODS: Data were obtained from the Pennsylvania Health Care Cost Containment Council, Division of In-Patient Statistics, regarding all cases of third- and fourth-degree perineal lacerations that occurred during a 2-year period (from January 1990 through December 1991). All subsequent pregnancies in this group of women over the next 10 years were identified, and the rate of recurrence of sphincter tears and risk factors for recurrence were analyzed. RESULTS: The rate of anal sphincter lacerations was 7.31% (n = 18,888) during the first 2 years of study (1990-1991). In the next 10 years, these patients with prior lacerations were delivered of 16,152 pregnancies. Of these, 1,162 were by cesarean. Among the 14,990 subsequent vaginal deliveries, 864 (5.76%) had a recurrence of a third- or fourth-degree laceration. Women with prior fourth-degree lacerations had a much higher rate of recurrence than those with prior third-degree laceration (7.73% versus 4.69%). The rate for recurrent lacerations was significantly lower than the rate for initial lacerations (odds ratio 1.29, 95% confidence interval [CI] 1.2-1.4). Forceps delivery with episiotomy had the highest risk for recurrent laceration (17.7%, odds ratio 3.6, 95% CI 2.6-5.1), whereas vacuum use without episiotomy had the lowest risk (5.88%, odds ratio 1.0, 95% CI 0.6-1.7). CONCLUSION: Prior anal sphincter laceration does not appear to be a significant risk factor for recurrence of laceration. Operative vaginal delivery, particularly with episiotomy, increases the risk of recurrent laceration as it does for initial laceration. LEVEL OF EVIDENCE: III.     

Decreasing the incidence of anal sphincter tears during delivery

OBJECTIVE: To estimate if an interventional program causes a decrease in the frequency of anal sphincter ruptures. METHODS: A total of 12,369 vaginal deliveries between 2002 and March 2007 were enrolled in the interventional cohort study. Slowing the delivery of the infant's head and instructing the mother not to push while the head is delivered was the intervention. Data were analyzed in relation to occurrence of anal sphincter tears. RESULTS: The proportion of parturients with anal sphincter tears decreased significantly during the study period from 4.03% (285 of 7,069) to 1.17% (42 of 3,577) (P<.001). A similar decrease was observed for instrumental deliveries (from 16.26% to 4.90%; P<.001) and noninstrumental deliveries (from 2.70% to 0.72%; P<.001). Although the number of patients with fourth-degree anal sphincter ruptures from 2002 through 2004 was 10, 13, and 11 per year, respectively, there was just one fourth-degree anal sphincter rupture during the whole study period of 18 months (P<.001). The number of episiotomies increased from 13.9% (980 of 7,069) in the years 2002-2004, to 23.1% during the first 9 months of the intervention (416 of 1,776; P<.001), but decreased to 21.1% (381 of 1,801) during the last 9 months of the intervention. CONCLUSION: As a result of this intervention the number of anal sphincter ruptures was reduced from 4.03% to 1.17%. LEVEL OF EVIDENCE: II.     

Lower genital tract and anal sphincter trauma

Anal incontinence occurs more frequently in women but its incidence is grossly underestimated because of under-reporting. Obstetric trauma is a major cause of anal incontinence but it is only recently that attention has been focused on this subject. Episiotomy and choice of instrument at assisted delivery have been subjected to randomized trials but some issues, such as the benefit of episiotomy in instrumental delivery, have not been addressed. The management of acute anal sphincter rupture is inconsistent and, although studies report on the sub-optimal outcome, evidence-based guidelines are currently awaiting publication. Training in perineal anatomy and repair is poorly taught, and there is wide variation in classification of perineal tears. Consequently anal sphincter tears are being missed at delivery and/or inappropriately managed. This chapter aims to highlight these issues based on previous and current teaching and to recommend a protocol based on the best available evidence.