Changes in anal anatomy following vaginal delivery revealed by anal endosonography

Risk of obstetric anal sphincter injuries (OASIS) and anal incontinence: A meta-analysis

BACKGROUND

Obstetric anal sphincter injuries (OASIS) are the commonest cause of anal incontinence in women of reproductive age. We determined the risk of anal sphincter defects diagnosed by ultrasound, and the risk of anal incontinence in (i) all women who deliver vaginally, (ii) in women without clinical suspicion of OASIS, and (iii) after primary repair of sphincter injury, by systematic review.

METHODS

We searched major databases until June 2018, without language restrictions. Random effects meta-analysis was used to obtain pooled estimates of ultrasound diagnosed OASIS and risk of anal incontinence symptoms at various time points after delivery, and of persistent sphincter defects after primary repair. We reported the association between ultrasound diagnosed OASIS and anal incontinence symptoms using relative risk (RR) with 95 % CI.

RESULTS

We included 103 studies involving 16,110 women. Of all women who delivered vaginally, OASIS were diagnosed on ultrasound in 26 % (95 %CI, 21-30, I² = 91 %), and 19 % experienced anal incontinence (95 %CI, 14-25, I² = 92 %). In women without clinical suspicion of OASIS (n = 3688), sphincter defects were observed in 13 % (10-17, I² = 89 %) and anal incontinence experienced by 14 % (95 % CI: 6-24, I² = 95 %). Following primary repair of OASIS, 55 % (46-63, I² = 98 %) of 7549 women had persistent sphincter defect with 38 % experiencing anal incontinence (33-43, I² = 92 %). There was a significant association between ultrasound diagnosed OASIS and anal incontinence (RR 3.74, 2.17-6.45, I² = 98 %).

INTERPRETATION

Women and clinicians should be aware of the high risk for sphincter defects following vaginal delivery even when clinically unsuspected. This underlines the need of careful and systematic perineal assessment after birth to mitigate the risk of missing OASIS. We also noted a high rate of persistent defects and symptoms following primary repair of OASIS. This dictates the need for provision of robust training for clinicians to achieve proficiency and sustain competency in repairing OASIS.

The evaluation of the effect of vaginal delivery and aging on anal sphincter anatomy and function

OBJECTIVE

This study was conducted to evaluate the effect of vaginal delivery and aging on anal sphincter anatomy and function.

METHOD

Asymptomatic thirty women were included in this prospective study. Group 1 included 10 women (age range: 18-50) who had never been pregnant. Group 2 included 10 women (age range: 18-50) who had vaginal delivery. Group 3 included 10 women over 50 who had vaginal delivery.

RESULTS

There was no statistically significant difference between the three groups in terms of resting and squeeze pressures. It was found that sphincter thickness showed statistically significant difference between the group 1 and group 3, and also group 2 and group 3. There was not statistically significant difference between the group 1 and group 2 in terms of sphincter thickness. There was a positive correlation between the age and sphincter thickness in all groups. In terms of sphincter thickness and pressure findings there was a positive correlation between the squeeze pressure and external anal sphincter thickness only in group 3.

CONCLUSION

The vaginal delivery did not have a negative influence on the structure and function of the anal sphincter in asymptomatic women. However, it was found that anal sphincter thickness changed strongly in a positive manner with aging.

[Applicability of 3/4D transperineal ultrasound for the diagnosis of anal sphincter injury during the immediate pospartum]

BACKGROUND

The most common cause of anal sphincter injuries in women is vaginal birth. Endo-anal ultrasound is currently used for the diagnosis of anal sphincter defect. However, due to the inconvenience caused, it is not an applicable technique during the immediate post-partum. The aim of this study was to determine whether transperineal ultrasound in 3/4D is a useful diagnostic method for the assessment of anal sphincter during the immediate post-partum.

MATERIAL AND METHODS

A prospective study was conducted on the vaginal deliveries performed between September 2012 and June 2013 in the Valme University Hospital (Seville). Obstetric and foetal parameters that could influence the onset of perineal tears were studied. The patients underwent a transperineal 3/4D ultrasound and a multislice study (48hours after birth).

RESULTS

The study included 146 puerperal women. The sphincter complex was assessed in all of them during the immediate post-partum. External anal injuries were observed in 10.3% of the cases. In 8.2% of cases, the primary suture of the external anal sphincter was detected during ultrasound examination, and 2.1% of asymptomatic lesions were diagnosed only with post-partum ultrasound. None of the patients reported discomfort or pain.

CONCLUSIONS

The 3-dimensional transperineal ultrasound is helpful in determining the primary repair of the anal sphincter during the immediate post-partum, with no discomfort for patients, as well as for establishing those early sphincter injuries that go unnoticed during vaginal delivery.

Effect of vaginal delivery and ageing on the anatomy of the female anal canal assessed by three-dimensional anorectal ultrasound

AIM

The effect of vaginal delivery and ageing on the anatomy of the anal canal was assessed using three-dimensional anorectal ultrasound to determine the interobserver reliability.

METHOD

One-hundred and eighteen asymptomatic women without sphincter damage were grouped according to parity and mode of delivery. They were then stratified by age (≤50 years vs >50 years). Group I consisted of 35 nulliparous women, of mean ages 36 years (n = 20) and 62 years (n = 15), Group II consisted of multiparous women, having one or more vaginal deliveries (n = 43), of mean ages 43 years (n = 20) and 60 years (n = 23) and Group III consisted of women who had a Caesarean section (n = 40) of mean ages 41 years (n = 20) and 56 years (n = 20). The groups were compared with regard to the length and the thickness of the external anal sphincter, the internal anal sphincter, the posterior external sphincter and the puborectalis in all quadrants and the anterior gap. Interobserver variability was assessed.

RESULTS

In women having vaginal delivery the length of the anterior external sphincter was shorter (P = 0.0004) and the gap was longer (P = 0.0306). The external sphincter tended to be thinner in individuals having vaginal delivery (P = 0.0677) and in those subjects over 50 years of age having had a vaginal delivery (P = 0.0164). In nulliparous women, the internal sphincter was thicker in subjects over 50 years of age (P = 0.0229). The intraclass correlation coefficient was 0.755-0.916 for sphincter muscle and gap length and 0.446-0.769 for muscle thickness.

CONCLUSION

Vaginal delivery was associated with a shorter anterior external sphincter, a longer gap and a thinner anterior external sphincter in asymptomatic women. Age was correlated with sphincter thickness, and nulliparous women >50 years of age had a thicker internal sphincter. Three-dimensional ultrasound was found to be a reliable method for measuring anal structures.

[Unusual perineal pain in postpartum period: contribution of perineal ultrasound]

We report two cases of persistent [correction of persistant] perineal pain in postpartum period due to transfixation of the anus with a suture and the contribution of perineal ultrasound in the diagnosis of unusual perineal pain.

The prevalence of occult obstetric anal sphincter injury following childbirth--literature review

OBJECTIVE

To calculate the published prevalence of ultrasound-detected occult anal sphincter damage associated with different modes of delivery.

METHODS

A search of the English language literature for articles using keywords describing the prevalence of ultrasound-diagnosed anal sphincter injury following childbirth. The weighted mean prevalence of occult anal sphincter injury was calculated in the following groups: (1) primiparous women (unselected); (2) primiparous women after an unassisted normal vaginal delivery; (3) multiparous women (unselected); (4) following forceps delivery; (5) following ventouse delivery; (6) following cesarean section.

RESULTS

Nineteen articles described ultrasound-diagnosed occult anal sphincter injury. The prevalence in unselected primiparous women (excluding cesarean section) was 29.2% (288/983). After unassisted vaginal delivery in primiparae the prevalence was 21.7% (74/341). The incidence in multiparous women (unselected) is 32.3% (107/331); following forceps delivery 49.1% (131/267) and with ventouse delivery it is 45.2% (66/146). Only one woman (in 173 cases) had anal sphincter injury following cesarean section.

CONCLUSIONS

After a review of the literature, occult anal sphincter injury is mostly associated with the first vaginal delivery and is particularly high following instrumental deliveries. Ventouse is less traumatic than forceps. Cesarean section is protective to the anal sphincter.

Age effects on internal anal sphincter thickness and diameter in nulliparous females

PURPOSE

Age can affect the delicate physiologic balance of the internal anal sphincter diameters and pressure governed by Laplace's law. This study compares the effect of aging on the internal anal sphincter thickness and diameter in younger and older nulliparous females without symptoms of fecal incontinence undisturbed by an endoanal probe.

METHODS

Magnetic resonance images were selected from a large database of nulliparous females to form two groups: "younger" females, aged 30 years and younger (n = 32), and "older" females, aged 50 years and older (n = 32). All patients were scanned without endoanal coils to allow undistorted measurement of the internal anal sphincter diameters. Inner and outer diameters were measured from axial magnetic resonance images and used to calculate sphincter thickness and mean radius by two independent investigators blinded to patient age.

RESULTS

The mean age in the younger group was 26 +/- 2.8 years, whereas that of the older group was 61.8 +/- 7.6 years. Older females had a 33 percent thicker internal anal sphincter (younger vs. older: 4.5 +/- 0.7 vs. 5.9 +/- 1 mm; P < 0.001), a 20 percent larger inner diameter (7.1 +/- 1.3 vs. 8.5 +/- 1.8 mm; P = 0.001), and a 27 percent larger outer diameter (16 +/- 2.1 vs. 20.3 +/- 3.3 mm; P < 0.001) than younger females. Neither sphincter thickness nor inner or outer diameter correlated with body mass index.

CONCLUSIONS

There is an increase in internal anal sphincter thickness, inner diameter, and outer diameter, which correlates with age in asymptomatic nulliparous females.

Three-dimensional transperineal sonographic characteristics of the anal sphincter complex in nulliparous women

OBJECTIVE

To explore the morphological characteristics and normal biometry of the anal sphincter complex in nulliparous Chinese women using three-dimensional (3D) transperineal ultrasound.

METHODS

3D sonographic data from 55 nulliparous Chinese women (aged 19-38 years) who had no pelvic organ prolapse and no symptoms of pelvic floor dysfunction were retrieved from an image dataset and analyzed by offline post-processing. The morphological characteristics of the external and internal anal sphincters, puborectalis muscle and perineal body were assessed in the sagittal, coronal and axial views.

RESULTS

The external anal sphincter had three sonographic components: the circular main body, a subcutaneous part and an extension portion. It was significantly thinner at 12 o'clock than at the 3, 6 and 9 o'clock positions. The internal anal sphincter was seen as dark echolucent strips of equal thickness. In the mid-sagittal view, it started from the anal verge and ended at the anorectal junction. The perineal body was an ovoid structure covering the upper margin of the external sphincter, while the puborectalis muscle was banana-shaped in the sagittal view and was located behind the anorectal junction, extending downward along the inferior margin of the posterior external sphincter extension. Sonographic characteristics of the anal sphincter complex did not vary with age, weight, height or body mass index.

CONCLUSIONS

3D transperineal ultrasound clearly demonstrates the spatial relationships of each component of the anal sphincter complex. This should allow standardized measurement of the complex for investigations of its function.

Effect of vaginal delivery on endosonographic anal sphincter morphology

OBJECTIVE

To describe the effect of vaginal delivery with no clinically recognized sphincter tear on endosonographic anal sphincter morphology and sphincter pressure and to relate endosonographic results to anal sphincter pressure and anal incontinence score.

STUDY DESIGN

Thirty-two nullipara underwent anal endosonography and anal manometry in the third trimester of pregnancy, 2 weeks and 6 months post-partum. The sphincter defect scores (1-16) and the thickness and length of the sphincters were measured by endosonography, and sphincter pressures and manometric sphincter lengths were determined. The Wexner incontinence score (1-20) was used to classify anal incontinence 6 months post-partum.

RESULTS

Five (16%) women had small endosonographic anal sphincter defects (score 3-4) before delivery. Eight women (25%; confidence interval 11-43%) had new defects detected post-partum, five small, one moderate (score 7), and two large (score 10-11). Six (75%) of eight women with new defects post-partum had undergone episiotomy versus five (21%) of 24 women with no new defects (p = 0.02). Six months after delivery 16 (50%) women reported anal incontinence, and there was a positive correlation between the endosonographic defect score 6 months post-partum and the Wexner incontinence score. The sphincter was significantly longer during pregnancy than 6 months post-partum.

CONCLUSION

New sphincter defects may arise after vaginal delivery without any clinically recognizable sphincter tear. There is a positive correlation between the endosonographic defect score 6 months post-partum and the Wexner incontinence score.

Endosonographic characteristics of the anal sphincter complex in primigravid Sri Lankan women

OBJECTIVE

To determine the endosonographic anatomy of the anal sphincter complex in primigravid Sri Lankan women.

METHOD

This is an observational study of 95 primigravid women admitted to an antenatal ward. They were examined using anal endosonography and data from subjects without sphincter injury were analyzed to describe anal sphincter morphology. Individual anal canal components were measured at defined levels, and the relationship of individual measurements with age and body mass index was calculated.

RESULTS

Ninety-three of 95 women had no anal sphincter damage. The puborectalis sling (mean 5.5 mm, S.D. 0.77) forms the upper most border of the sphincter complex. The mean width of the deep external sphincter was 4.3 mm (S.D. 0.61); that of the superficial external sphincter was 4.5 mm (S.D. 0.56); and that of the internal anal sphincter at the mid anal canal was 2.1 mm (S.D. 0.21). The intersphincteric space (mean 2.1 mm, S.D. 0.26) could be distinguished sonographically in all subjects. The mean width of the anterior ring of the subcutaneous component was 3.8 mm (S.D. 1.01). The perineal body was sonographically identified in 60%.

CONCLUSION

A set of normal values for the anal sphincter components in Sri Lankan primigravid women was established.

Alteration of anal sphincter morphology following vaginal delivery revealed by multiplanar anal endosonography

OBJECTIVE

To assess morphologic change in the anal sphincters in the absence of endosonographic evidence of trauma after vaginal delivery.

DESIGN

Prospective observational study.

SETTING

District general hospital.

POPULATION

Consecutively booked nulliparous pregnant women attending antenatal clinic.

METHODS

All women were examined using three-dimensional anal endosonography, simple manometry and had questionnaire assessment of incontinence before and after delivery.

MAIN OUTCOME MEASURES

Components of the anal canal were measured in the axial, sagittal and coronal planes and paired pre- and post-delivery examinations were compared. Any changes were related to changes in continence and anal canal manometry.

RESULTS

Twenty-two women had a vaginal delivery and no endosonographic evidence of perineal trauma after delivery. After delivery, there was significant shortening of the length of the anterior external anal sphincter [EAS] (mean 21.7 vs 20.5 mm, P = 0.02) when measured in the sagittal plane, which increased in anterior angulation with respect to the axis of the anal canal (10 degrees vs 13.8 degrees, P = 0.03). In the axial plane, no change was seen in the thickness of any of the sphincter components after delivery. None of these morphologic changes correlated with changes in manometry or continence score.

CONCLUSIONS

Anal sphincter morphology changes after an otherwise atraumatic vaginal delivery. This change does not correlate with any functional symptoms.

Female anal sphincter: age-related differences in asymptomatic volunteers with high-frequency endoanal US

PURPOSE

To evaluate endoanal ultrasonographic (US) anatomy in a large group of nulliparous women by using a high-frequency 10-MHz transducer to define normal age-related differences in sphincter morphology.

MATERIALS AND METHODS

One hundred fifty asymptomatic nulliparous women (mean age, 31 years; range, 19-80 years) underwent endoanal US with a high-frequency 10-MHz transducer. Anal canal structures were measured at high, middle, and low levels and were correlated with age by using the Pearson simple linear correlation coefficient.

RESULTS

Internal sphincter thickness showed a highly significant positive correlation with age at both sites at which it was measured (high anal canal, r = 0.34, P <.001; middle anal canal, r = 0.33, P <.001). External sphincter thickness showed a highly significant negative correlation with age at all sites measured (high anal canal, r = -0.65, P <.001; middle anal canal, r = -0.49, P <.001; low anal canal, r = -0.21, P =.012). There was no significant correlation between age and thickness of subepithelial tissue, longitudinal muscle, or puborectalis muscle. Subjects whose internal sphincter showed mixed echogenicity were significantly older than those whose internal sphincter was uniformly hypoechoic (mean, 47.4 vs 34.6 years; P <.001). Subjects with mixed internal sphincter echogenicity also had a significantly thinner external sphincter at high (mean thickness, 3.8 vs 4.6 mm; P <.001) and middle (mean thickness, 3.7 vs 4.1 mm; P =.03) anal canal levels.

CONCLUSION

At older ages there are increased internal anal sphincter thickness and decreased external anal sphincter thickness. Diagnosis of external sphincter atrophy on the basis of sphincter thinning requires that one distinguish between abnormal thinning and age-related differences.

The effects of childbirth on the pelvic-floor

Basically, vaginal delivery is associated with the risk of pelvic floor damage. The pelvic floor sequelae of childbirth includes anal incontinence, urinary incontinence and pelvic organ prolapse. Pathophysiology, incidence and risk factors for the development of the respective problems are reviewed. Where possible, recommendations for reducing the risk of pelvic floor damage are given.

Neuronal innervation of urethral and anal sphincters: surgical anatomy and clinical implications

The present review describes the neuronal innervation of the external urethral and anal sphincters. A knowledge of this innervation helps in understanding the clinical symptoms of urinary and anorectal pathology, and in choosing the appropriate technique of nerve localization or block. An ability to locate the pudendal nerve, on the basis of surgically documented anatomy, has important diagnostic and therapeutic advantages. It can be used to study the integrity of pelvic floor muscles, in biofeedback training, nerve blocks, pudendal canal decompression, chronic stimulation trials to treat urinary or faecal incontinence, and in nerve conduction studies or evoked potential recordings. Furthermore, the superficial location of the sphincteric innervation in the perineum and ischiorectal fossa renders the nerve branches susceptible to injury during operative correction of urinary or faecal incontinence. Supported by a knowledge of anatomy, we can make firm recommendations on which to base safe surgical techniques that avoid damage to urethral and anal sphincteric innervation.