Int Urogynecol J DOI 10.1007/s00192-014-2577-5
ORIGINAL ARTICLE
Is there a correlation between levator ani and urethral sphincter complex status on 3D ultrasonography? A. C. Santiago & D. E. O’Leary & L. H. Quiroz & S. Abbas Shobeiri
Received: 16 July 2014 / Accepted: 10 November 2014 # The International Urogynecological Association 2014
Abstract Introduction and hypothesis To determine the correlation between levator ani deficiency (LAD) and urethral sphincter complex measurements as visualized on 3D endovaginal ultrasonography, and to compare the LAD score with continence status. Methods This was a retrospective analysis of patients seen at our institution between January 2011 and August 2013. Patients were dichotomized into those with urodynamic stress urinary incontinence (SUI) and those with no SUI. Levator ani status was evaluated using a validated scoring system yielding scores of 0 – 6 (normal levator ani/mild LAD), 7 – 12 (moderate LAD), and 13 – 18 (severe LAD). The length, horizontal diameter, and cross-sectional area of the urethra, and the length, width, and the area of the rhabdomyosphincter and smooth muscle sphincter were likewise measured using 3D ultrasound volumes. Results Of the 80 patients included, 54 (67.5 %) had SUI and 26 (32.5 %) were continent. 18 (22.5 %) had evidence of mild LAD, 54 (67.5 %) had moderate LAD, and 8 (10.0 %) had severe LAD. Among patients with SUI, those with normal levator ani muscles or mild LAD had greater urethral smooth muscle width than those with moderate and severe LAD (p= 0.0238). A greater proportion of patients with SUI also had moderate to severe LAD than continent patients (p=0.0177, OR 3.59, 95 % CI 1.21 – 10.65). There was no difference in LAD distribution by type of stress incontinence (presence or absence of intrinsic sphincter deficiency; p=0.2377). Conclusions LAD and urethral sphincter complex status, as visualized on 3D ultrasonography, are independent factors. A. C. Santiago : D. E. O’Leary : L. H. Quiroz : S. A. Shobeiri (*) Division of Female Pelvic Medicine and Reconstructive Surgery, Department of Obstetrics and Gynecology, University of Oklahoma Health Sciences Center, 920 Stanton L. Young Boulevard WP 2410, P.O. Box 26901, Oklahoma City, OK 73190, USA e-mail: [email protected]
Moderate to severe LAD is more prevalent in patients with SUI. Keywords Levator ani deficiency . Stress urinary incontinence . Three-dimensional endovaginal ultrasonography . Urethral sphincter complex
Introduction With the recent advances in pelvic floor imaging modalities, it has become evident that levator ani muscle injury plays an important role in the development of pelvic floor dysfunction [1]. Although it has already been established that levator ani muscle injury increases the risk of pelvic organ prolapse [2–4], its role in lower urinary tract symptoms, more specifically in stress urinary incontinence (SUI), is still not completely understood and deserves attention. The urinary continence control system can be divided anatomically into two parts: the urethral support and the sphincteric closure system [5]. The urethral support system consists of all the structures extrinsic to the urethra that provide a supportive layer upon which the urethra rests [6]. The levator ani muscle is a major component of the urethral support system and provides the lateral support for the pubocervical fascia. Active contraction of the different subgroups of the levator ani muscle elevates the bladder neck and their relaxation allows its descent. In addition, the normal constant activity of the levator ani muscle supports the bladder neck during normal activities. On the other hand, the sphincteric closure system of the urethra is composed of striated muscle, smooth muscle, and the vascular elements within the submucosa. Each is believed to contribute equally to the resting urethral closure pressure [5]. The anatomic disposition of these muscles is such that the outer layer of the urethra is formed by the striated muscle sphincter at 20 – 80 % of the
Int Urogynecol J
total urethral length. The smooth muscle sphincter has an inner longitudinal and an outer circular layer, which lie inside the striated muscle sphincter and are present throughout the upper 80 % of the urethra [7]. It could therefore expected that muscle deficiencies in either the urethral support system or sphincteric closure system are reflected in patients’ urethral function parameters or urinary symptoms. However, findings in published studies [8, 9] reveal conflicting data and active debate still continues regarding the exact nature of the pathophysiologic mechanisms involved in SUI. In one study [10], urethral function observed during the first year after delivery did not differ in women with and without levator ani muscle injury. Women with and without levator ani defects were able to increase their intraurethral pressure during a Kegel effort by a similar amount. The levator ani muscle is arranged in a unique threedimensional structure that makes it accessible by ultrasonography [11, 12] and magnetic resonance imaging (MRI) [13, 14]. In the same way, the urethral sphincter musculature can also be easily visualized and readily measured using endovaginal ultrasonography (EVUS) [15, 16], intraurethral ultrasonography [17, 18] and MRI [19–21]. The levator ani muscle and the urethral rhabdomyosphincter are both skeletal muscles. Determining whether or not atrophy of the levator ani muscle and rhabdomyosphincter occur concurrently and relate to patients’ continence status would improve our basic understanding of the continence mechanism and may prove valuable for planning treatment strategies in incontinent women. Current management of SUI still has a fairly high rate of failure [22]. It is hoped that by understanding the morphologic relationship of the different muscle groups that make up the pelvic floor, a more individualized or defect-targeted management can be achieved in patients with SUI. The aims of the study were to determine whether there was a correlation between levator ani deficiency (LAD) and urethral sphincter complex measurements as visualized on 3D ultrasonography and to compare the LAD score with continence status.
Materials and methods This was a retrospective cross-sectional study approved by our Institutional Review Board. Patients who underwent EVUS for clinical indications or were included in varied research protocols were considered. In all such cases, ultrasound imaging was performed by any of the three attending physicians in our division (D.E.O., L.H.Q., S.A.S.) with extensive training in pelvic floor ultrasound imaging. Interpretation was done by one research fellow (A.C.S.) and confirmed by S.A.S. Exclusion criteria were incomplete medical record or urodynamic report, history of previous antiincontinence procedure or surgery, and poor quality
ultrasound images of the pelvic floor. “Poor quality” ultrasound images were those with no identifiable sonographic landmarks, which include the pubic bone, bladder, urethra, vagina and rectum. A total of 80 patients seen from January 2011 to August 2013 were included. Patients were dichotomized into those with SUI (documented on urodynamics) and those without SUI. Ultrasound imaging technique Ultrasound imaging was performed at the time of the primary visit using a BK Medical Ultrafocus machine (Peabody, MA). All ultrasound examinations were performed in the office setting, with the patient in the dorsal lithotomy position and with the hips flexed and slightly abducted. No preparation was required and the patients were recommended to have a comfortable volume of urine in the bladder. No rectal or vaginal contrast material was used. To avoid excessive pressure on the surrounding structures that might distort anatomy, the probe was inserted into the vagina in a neutral position. The 8838 probe used in this study had an internal automated motorized system that allowed acquisition of 1,020 aligned radial 2D images over a distance of 6 cm every 0.35 degrees, without any movement of the probe within the cavity. EVUS volumes were digitally stored for future analysis [23]. Levator ani muscle scoring system Based on published studies [3, 11, 12], the levator ani muscle was divided into three subgroups: the puboperinealis/puboanalis (PA), the puborectalis (PR), and the iliococcygeus/pubococcygeus (PV). The PA subgroup, which is poorly studied, is the perineal stabilizer, while the PR is the squeezer, and the PV is the elevator. These three subgroups contribute similar muscle bulk to the levator ani and as such receive a similar score in the LAD scoring system [24]. Each subgroup was evaluated in the specific axial plane where the full length of the muscle could be visualized. Anatomically, muscle loss is replaced by fatty infiltration of the muscles and on ultrasonography, this increased water content is visualized as decreased or absent echogenicity. The following validated scoring system was used [12]: 0 no muscle defect, 1 minimal defect with 50 % or less muscle loss, 2 major defect with more than 50 % muscle loss, and 3 total absence of muscle (Fig. 1). When scores from each side (right and left) were summed up, possible scores ranged from 0 (no defect) to 6 (total muscle absence) and a cumulative score of 0 – 18 was possible for all the three muscle groups. Scores were then categorized as normal levator ani/mild LAD (0 – 6), moderate LAD (7 – 12), or severe LAD (≥13).
Int Urogynecol J Fig. 1 Levator ani deficiency scoring system
Urethral sphincter complex measurements Urethral sphincter measurements were based on prior studies that correlated histopathology with the sonographic view of the urethral sphincter complex [16]. Measurements were obtained on different planes as follows: A. Midsagittal plane 1. Urethral length – measured from the urethrovesical junction up to the external urethral meatus (Fig. 2a). 2. Smooth muscle sphincter length, width, and area – measured along the proximal part of the urethra (Fig. 2b). B. Coronal plane: Rhabdomyosphincter length, width, and area – measured medial to the symphysis pubis on either side (Fig. 2c). C. Axial plane: Urethral horizontal diameter and crosssectional area – a line perpendicular to the midpoint of the urethra was drawn on the midsagittal plane and the 3D cube was manipulated on the axial plane to reach this level. Urethral horizontal diameter was then measured (Fig. 2d). Urethral cross-sectional area was subsequently computed by dividing the urethral horizontal diameter by 2 to obtain the radius (r). Cross-sectional area was calculated as πr2. Statistical analyses Statistical analyses were performed using SAS version 9.3 (SAS Institute, Cary, NC). Summary statistics were calculated
for the patient population. Two-way ANOVA, Spearman’s rank and Kendall’s tau-b correlations were used to determine the relationship between LAD score and urethral sphincter complex measurements. Chi-square or Fisher’s exact tests were used to compare LAD score with continence status. T-test was used to compare the urethral sphincter complex measurements between those with SUI and those without SUI. A p value of
ORIGINAL ARTICLE
Is there a correlation between levator ani and urethral sphincter complex status on 3D ultrasonography? A. C. Santiago & D. E. O’Leary & L. H. Quiroz & S. Abbas Shobeiri
Received: 16 July 2014 / Accepted: 10 November 2014 # The International Urogynecological Association 2014
Abstract Introduction and hypothesis To determine the correlation between levator ani deficiency (LAD) and urethral sphincter complex measurements as visualized on 3D endovaginal ultrasonography, and to compare the LAD score with continence status. Methods This was a retrospective analysis of patients seen at our institution between January 2011 and August 2013. Patients were dichotomized into those with urodynamic stress urinary incontinence (SUI) and those with no SUI. Levator ani status was evaluated using a validated scoring system yielding scores of 0 – 6 (normal levator ani/mild LAD), 7 – 12 (moderate LAD), and 13 – 18 (severe LAD). The length, horizontal diameter, and cross-sectional area of the urethra, and the length, width, and the area of the rhabdomyosphincter and smooth muscle sphincter were likewise measured using 3D ultrasound volumes. Results Of the 80 patients included, 54 (67.5 %) had SUI and 26 (32.5 %) were continent. 18 (22.5 %) had evidence of mild LAD, 54 (67.5 %) had moderate LAD, and 8 (10.0 %) had severe LAD. Among patients with SUI, those with normal levator ani muscles or mild LAD had greater urethral smooth muscle width than those with moderate and severe LAD (p= 0.0238). A greater proportion of patients with SUI also had moderate to severe LAD than continent patients (p=0.0177, OR 3.59, 95 % CI 1.21 – 10.65). There was no difference in LAD distribution by type of stress incontinence (presence or absence of intrinsic sphincter deficiency; p=0.2377). Conclusions LAD and urethral sphincter complex status, as visualized on 3D ultrasonography, are independent factors. A. C. Santiago : D. E. O’Leary : L. H. Quiroz : S. A. Shobeiri (*) Division of Female Pelvic Medicine and Reconstructive Surgery, Department of Obstetrics and Gynecology, University of Oklahoma Health Sciences Center, 920 Stanton L. Young Boulevard WP 2410, P.O. Box 26901, Oklahoma City, OK 73190, USA e-mail: [email protected]
Moderate to severe LAD is more prevalent in patients with SUI. Keywords Levator ani deficiency . Stress urinary incontinence . Three-dimensional endovaginal ultrasonography . Urethral sphincter complex
Introduction With the recent advances in pelvic floor imaging modalities, it has become evident that levator ani muscle injury plays an important role in the development of pelvic floor dysfunction [1]. Although it has already been established that levator ani muscle injury increases the risk of pelvic organ prolapse [2–4], its role in lower urinary tract symptoms, more specifically in stress urinary incontinence (SUI), is still not completely understood and deserves attention. The urinary continence control system can be divided anatomically into two parts: the urethral support and the sphincteric closure system [5]. The urethral support system consists of all the structures extrinsic to the urethra that provide a supportive layer upon which the urethra rests [6]. The levator ani muscle is a major component of the urethral support system and provides the lateral support for the pubocervical fascia. Active contraction of the different subgroups of the levator ani muscle elevates the bladder neck and their relaxation allows its descent. In addition, the normal constant activity of the levator ani muscle supports the bladder neck during normal activities. On the other hand, the sphincteric closure system of the urethra is composed of striated muscle, smooth muscle, and the vascular elements within the submucosa. Each is believed to contribute equally to the resting urethral closure pressure [5]. The anatomic disposition of these muscles is such that the outer layer of the urethra is formed by the striated muscle sphincter at 20 – 80 % of the
Int Urogynecol J
total urethral length. The smooth muscle sphincter has an inner longitudinal and an outer circular layer, which lie inside the striated muscle sphincter and are present throughout the upper 80 % of the urethra [7]. It could therefore expected that muscle deficiencies in either the urethral support system or sphincteric closure system are reflected in patients’ urethral function parameters or urinary symptoms. However, findings in published studies [8, 9] reveal conflicting data and active debate still continues regarding the exact nature of the pathophysiologic mechanisms involved in SUI. In one study [10], urethral function observed during the first year after delivery did not differ in women with and without levator ani muscle injury. Women with and without levator ani defects were able to increase their intraurethral pressure during a Kegel effort by a similar amount. The levator ani muscle is arranged in a unique threedimensional structure that makes it accessible by ultrasonography [11, 12] and magnetic resonance imaging (MRI) [13, 14]. In the same way, the urethral sphincter musculature can also be easily visualized and readily measured using endovaginal ultrasonography (EVUS) [15, 16], intraurethral ultrasonography [17, 18] and MRI [19–21]. The levator ani muscle and the urethral rhabdomyosphincter are both skeletal muscles. Determining whether or not atrophy of the levator ani muscle and rhabdomyosphincter occur concurrently and relate to patients’ continence status would improve our basic understanding of the continence mechanism and may prove valuable for planning treatment strategies in incontinent women. Current management of SUI still has a fairly high rate of failure [22]. It is hoped that by understanding the morphologic relationship of the different muscle groups that make up the pelvic floor, a more individualized or defect-targeted management can be achieved in patients with SUI. The aims of the study were to determine whether there was a correlation between levator ani deficiency (LAD) and urethral sphincter complex measurements as visualized on 3D ultrasonography and to compare the LAD score with continence status.
Materials and methods This was a retrospective cross-sectional study approved by our Institutional Review Board. Patients who underwent EVUS for clinical indications or were included in varied research protocols were considered. In all such cases, ultrasound imaging was performed by any of the three attending physicians in our division (D.E.O., L.H.Q., S.A.S.) with extensive training in pelvic floor ultrasound imaging. Interpretation was done by one research fellow (A.C.S.) and confirmed by S.A.S. Exclusion criteria were incomplete medical record or urodynamic report, history of previous antiincontinence procedure or surgery, and poor quality
ultrasound images of the pelvic floor. “Poor quality” ultrasound images were those with no identifiable sonographic landmarks, which include the pubic bone, bladder, urethra, vagina and rectum. A total of 80 patients seen from January 2011 to August 2013 were included. Patients were dichotomized into those with SUI (documented on urodynamics) and those without SUI. Ultrasound imaging technique Ultrasound imaging was performed at the time of the primary visit using a BK Medical Ultrafocus machine (Peabody, MA). All ultrasound examinations were performed in the office setting, with the patient in the dorsal lithotomy position and with the hips flexed and slightly abducted. No preparation was required and the patients were recommended to have a comfortable volume of urine in the bladder. No rectal or vaginal contrast material was used. To avoid excessive pressure on the surrounding structures that might distort anatomy, the probe was inserted into the vagina in a neutral position. The 8838 probe used in this study had an internal automated motorized system that allowed acquisition of 1,020 aligned radial 2D images over a distance of 6 cm every 0.35 degrees, without any movement of the probe within the cavity. EVUS volumes were digitally stored for future analysis [23]. Levator ani muscle scoring system Based on published studies [3, 11, 12], the levator ani muscle was divided into three subgroups: the puboperinealis/puboanalis (PA), the puborectalis (PR), and the iliococcygeus/pubococcygeus (PV). The PA subgroup, which is poorly studied, is the perineal stabilizer, while the PR is the squeezer, and the PV is the elevator. These three subgroups contribute similar muscle bulk to the levator ani and as such receive a similar score in the LAD scoring system [24]. Each subgroup was evaluated in the specific axial plane where the full length of the muscle could be visualized. Anatomically, muscle loss is replaced by fatty infiltration of the muscles and on ultrasonography, this increased water content is visualized as decreased or absent echogenicity. The following validated scoring system was used [12]: 0 no muscle defect, 1 minimal defect with 50 % or less muscle loss, 2 major defect with more than 50 % muscle loss, and 3 total absence of muscle (Fig. 1). When scores from each side (right and left) were summed up, possible scores ranged from 0 (no defect) to 6 (total muscle absence) and a cumulative score of 0 – 18 was possible for all the three muscle groups. Scores were then categorized as normal levator ani/mild LAD (0 – 6), moderate LAD (7 – 12), or severe LAD (≥13).
Int Urogynecol J Fig. 1 Levator ani deficiency scoring system
Urethral sphincter complex measurements Urethral sphincter measurements were based on prior studies that correlated histopathology with the sonographic view of the urethral sphincter complex [16]. Measurements were obtained on different planes as follows: A. Midsagittal plane 1. Urethral length – measured from the urethrovesical junction up to the external urethral meatus (Fig. 2a). 2. Smooth muscle sphincter length, width, and area – measured along the proximal part of the urethra (Fig. 2b). B. Coronal plane: Rhabdomyosphincter length, width, and area – measured medial to the symphysis pubis on either side (Fig. 2c). C. Axial plane: Urethral horizontal diameter and crosssectional area – a line perpendicular to the midpoint of the urethra was drawn on the midsagittal plane and the 3D cube was manipulated on the axial plane to reach this level. Urethral horizontal diameter was then measured (Fig. 2d). Urethral cross-sectional area was subsequently computed by dividing the urethral horizontal diameter by 2 to obtain the radius (r). Cross-sectional area was calculated as πr2. Statistical analyses Statistical analyses were performed using SAS version 9.3 (SAS Institute, Cary, NC). Summary statistics were calculated
for the patient population. Two-way ANOVA, Spearman’s rank and Kendall’s tau-b correlations were used to determine the relationship between LAD score and urethral sphincter complex measurements. Chi-square or Fisher’s exact tests were used to compare LAD score with continence status. T-test was used to compare the urethral sphincter complex measurements between those with SUI and those without SUI. A p value of
