Chapter Outline
Retrograde and Antegrade Pyelography
Applications of Ultrasound in Evaluating Disorders of the Lower Urinary Tract and Pelvic Floor
Pelvic floor disorders include a broad array of interrelated clinical conditions that include urinary incontinence, pelvic organ prolapse, fecal incontinence, sensory abnormalities, and defecatory dysfunction. Bothersome symptoms may also stem from anatomic anomalies such as a urethral diverticulum, a paravaginal mass, or a surgical implant. In addition to a thorough clinical evaluation, multiple imaging modalities are now available to guide the clinician to the appropriate diagnosis and management. Beyond its clinical application, advanced imaging technology has an increasingly important role in our quest to understand the pathophysiology of pelvic floor disorders and the anatomic variations not apparent from the physical examination alone. The focus of this chapter is on describing the radiologic studies used in clinical practice and research by radiologists and pelvic floor specialists.
Intravenous Pyelography
Intravenous pyelography (IVP) is safe, inexpensive, and widely available, and it provides information about the anatomy of the urinary collecting system and functional status of the glomerular filtration apparatus ( Fig. 13.1 ). One of the most common indications for performing an IVP in urogynecology is to detect possible ureteral obstruction caused by gynecologic cancer, pelvic mass, pelvic organ prolapse, or after gynecologic surgery. With delayed films and tomography, IVP is also useful to diagnose certain uncommon conditions, such as ectopic ureter and ureterovaginal fistula. Once an essential urologic imaging modality, IVP has almost entirely been replaced by computed tomographic (CT) and magnetic resonance imaging (MRI). CT imaging is able to demonstrate axial, sagittal, and coronal views of the upper tract urinary system and offers superb image quality compared with IVP. In addition, some parenchymal defects, cysts, and tumors are better delineated with CT than IVP.
Retrograde and Antegrade Pyelography
Retrograde pyelography is performed to evaluate the ureters and intrarenal collecting system. In retrograde pyelogram, the contrast medium is injected into the upper urinary tract through a cone-tipped catheter placed at cystoscopy under fluoroscopic guidance. This approach is particularly useful for intraoperative evaluation of a ureteral obstruction because it has a unique ability to evaluate the ureter distal to the obstruction and thus can better define the extent of the ureteral abnormality. This approach is associated with a higher infection rate than antegrade pyelography and may be contraindicated in women with a known allergic reaction to contrast media or recent lower urinary tract trauma or surgery. The large amount of contrast medium injected and the pressure applied during retrograde pyelogram may result in anastomotic leak and extravasation, with systemic absorption of the contrast.
Antegrade pyelography can provide excellent opacification of the renal collecting system ( Fig. 13.2 ). This approach involves placing a small-gauge needle into the renal pelvis; it is rarely performed for diagnostic indications only and is usually performed only when there is another indication for percutaneous puncture of the kidney. To perform an antegrade pyelography, the patient is placed in a prone position. A flexible 20- or 22-gauge needle is inserted into the collecting system under ultrasound or fluoroscopic control after administration of intravenous contrast medium. An obstructed renal collecting system should be decompressed before contrast medium is injected, to avoid overdistention and urosepsis. Additional procedures, such as attempts at antegrade ureteral stenting, can then be performed to temporarily or permanently relieve the obstruction.
Cystography
Cystography is frequently performed to detect bladder injury after trauma, to diagnose fistulas between the bladder and the adjacent organs, and to confirm that a cystotomy or bladder fistula has healed after surgical repair. Vesicovaginal, vesicouterine, and vesicoenteric fistulas are diagnosed when contrast material from the bladder enters and opacifies the adjacent viscera ( Fig. 13.3 ). Absence of contrast in the adjacent viscera does not always exclude a fistula because the connecting tract may not be large enough to allow passage of a sufficient quantity of contrast to be seen radiographically.
To determine whether a cystotomy or fistula repair has healed, the bladder is filled slowly with contrast medium, and then is drained. A postvoid film is obtained to evaluate for extravasated contrast medium. Contrast from extraperitoneal leakage usually forms an irregularly shaped mass around the defect and remains there for a relatively long time. Contrast that has leaked from an intraperitoneal defect diffuses into the abdominal cavity and is rapidly absorbed through the peritoneal cavity.
Voiding Cystourethrography
A voiding cystourethrogram (VCUG) is a dynamic radiologic study that is used to diagnose structural bladder and urethral abnormalities with voiding and to evaluate for vesicoureteral reflux. A VCUG is also used to investigate suspected bladder fistula or suburethral diverticulum and to evaluate the integrity of the bladder or urethra after fistula or diverticula surgery ( Fig. 13.4 ).
Positive-pressure urethrography can be performed in conjunction with VCUG to maximize diagnostic accuracy. It can also be used during surgery to help expand and identify urethral diverticula and to test the integrity of repairs after resection. This study requires a Tratner catheter, which has two balloons, with an opening in the lumen of the catheter between the two balloons for contrast injections. The distal balloon is placed into the bladder, and the proximal (sliding) balloon is positioned just outside the external urethral meatus. The two inflated balloons create a temporary, closed system and allow the contrast injected into the urethra to opacify the diverticulum ( Fig. 13.5 ). Because of recent advances, ultrasound and MRI technology have replaced VCUG as the primary imaging modality in diagnosing urethral and bladder abnormalities.
Video-Cystourethrography
Video-cystourethrography combines a fluoroscopic voiding cystourethrogram with simultaneous intravesical, intraurethral, and intra-abdominal pressures and urine flow rate. Urethral sphincter electromyography (EMG) is often done simultaneously to assess neurogenic voiding disorders. Video-cystourethrography allows visual assessment of urethral sphincters and bladder function while synchronously recording urodynamic and EMG data, and is considered the reference standard of urodynamic investigation against which other techniques are compared. Some controversy exists regarding the indications for video-cystourethrography and whether it should be performed routinely or selectively. Some common indications include complex cases with equivocal results after multichannel urodynamic studies, failed incontinence surgery, and voiding disorders associated with neurologic diseases. See Chapter 11 for a thorough review of the technique and utility of video-urodynamic testing.
Ultrasound
Ultrasound offers real-time evaluation that can be obtained in an office setting and is well tolerated by patients. Other important advantages include the absence of ionized radiation, the wide availability, and acceptable cost-effectiveness. Recent advances in three-dimensional (3D) ultrasonography allow the clinician to simultaneously view axial, transverse, and coronal views and construct an accurate 3D image of the pelvic structures. Four-dimensional (4D) imaging involves real-time acquisition, providing an insight into functional anatomy and the changes that take place with straining and Valsalva maneuver. The diagnostic potential of 3D and 4D modalities is currently under investigation; once validated, it may become an important component in urogynecologic and urologic practice.
Several ultrasound techniques are available for evaluation of the lower urinary tract and pelvic floor. These include transabdominal (T-A), transvaginal (T-V), perineal (also referred to as translabial), introital, and transrectal approaches.
Techniques
Perineal and Introital Ultrasonography
For dynamic assessment, the T-V approach may exert a compressive effect on the lower urinary tract. Therefore, to prevent distortion of the anatomy of the lower urinary tract by probes, perineal (translabial) and introital approaches are used. Both techniques can be performed with the patient in dorsal lithotomy, semireclining, or standing positions. For a perineal approach, a curved array probe with frequency between 3.5 and 6 MHz is applied to the perineum or outside the labia majora. The introital technique uses a sector endovaginal probe with a frequency between 5 and 7.5 MHz, applied to the vaginal introitus, just underneath the urethral orifice. The examination begins by obtaining an image in the midsagittal plane, where the anatomic structures between the symphysis pubis and the posterior levator ani muscles are visualized: bladder neck, urethra, vagina, cervix, rectum, and anal canal ( Fig. 13.6 ). The pressure exerted by the transducer should be kept low but sufficient to obtain good images with high resolution. The presence of a full rectum may impair diagnostic accuracy and sometimes necessitates a repeat assessment after defecation. The bladder volume should be fixed on examination: 300 mL for the evaluation of dynamic changes of the bladder neck and <50 mL for the assessment of bladder wall thickness. The bladder volume can be estimated by either a T-A or T-V approach, although accuracy is not reliable for bladder volumes <50 mL.
Three-dimensional and 4D ultrasound technology allows a multiplanar display mode with visualization of cross-sectional planes. Figure 13.7 demonstrates four display modes using a 3D ultrasound system: (1) midsagittal, (2) coronal, (3) axial, and (4) rendered. The availability of postprocessing software allows manipulation and analysis of images remote from the time of the exam. Four-dimensional imaging allows the real-time acquisition of ultrasound data, with the ability to store cine-loops, which makes it feasible to evaluate dynamic changes in the pelvic floor, such as during a Valsalva maneuver.
T-V Ultrasonography
T-V ultrasound is performed with the patient in the dorsal lithotomy position. Various probes can be used for this approach. It may be performed with an electronic biplane (linear and transverse perpendicular arrays) 5- to 12-MHz probe (B-K Medical, Peabody, MA, USA) or a high multifrequency (9- to 16-MHz) 360° rotational mechanical probe (B-K Medical, Peabody, MA, USA). The biplane electronic probe provides two-dimensional sagittal and axial sectional imaging of the anterior and posterior compartments. A 3D reconstruction may then be performed to obtain sagittal, axial, coronal, and oblique sectional images ( Fig. 13.8 ).
Transrectal Ultrasonography
Transrectal ultrasound (also referred to as endoanal and endosonography) is performed with an intracavitary probe, similar to T-V ultrasound. Patients can be placed in the dorsal lithotomy position, may be prone, or may be in the left lateral position. The transducer should then be rotated to the 12-o’clock position anteriorly. The scan starts at the upper aspect of the puborectalis muscle and extends to the anal verge. In this view, the following anatomic layers are visualized: the subepithelial layer, which is hyperechoic; the internal anal sphincter, which appears as a hypoechoic ring; the longitudinal muscle (hyperechoic); and the external anal sphincter, which is the outmost layer and is hyperechoic ( Fig. 13.9 ). Three-dimensional reconstruction allows visualization of the structures in different planes as well as better localization of masses, abscesses, or fistulas.
Routine uses of ultrasound that have been most described in evaluating lower urinary tract and pelvic floor are listed in Box 13.1 .
| Bladder neck decent/mobility/opening at rest and on Valsalva |
| Postvoid residual volume |
| Intercurrent uterine and adnexal pathology |
| Uterine position |
| Bladder abnormalities (e.g., tumor, foreign body) |
| Urethral abnormalities (e.g., diverticulum) |
| Postoperative findings (e.g., bladder neck mobility; position of mesh, grafts, or implants) |
| Pelvic floor muscle defect |
| Pelvic floor descent |
| Anal sphincter defect |
Applications of Ultrasound in Evaluating Disorders of the Lower Urinary Tract and Pelvic Floor
Urinary Incontinence
Ultrasonography can be used to detect anatomic alterations associated with urinary incontinence, to help select the appropriate therapy, and to evaluate surgical outcomes and postoperative complications. A well-known sonographic finding in patients with overactive bladder is wavelike detrusor contractions accompanied by bladder neck opening. reported that an increase in mean bladder wall thickness is unique to detrusor overactivity. With a cutoff value of 5 mm, bladder wall thickness together with symptoms of overactive bladder had a sensitivity of 84% and specificity of 89% for detecting detrusor overactivity, compared with video-cystourethrography. The authors speculated that the increased bladder wall thickness in this disorder resulted from detrusor hypertrophy associated with increased isometric detrusor contraction, urethral sphincter volume, and urethral closure pressure. However, other authors have not been able to confirm this finding.
Ultrasonographic studies for stress incontinence have been used to provide quantitative measurements and qualitative descriptions of the lower urinary tract. , representing the German Association of Urogynecology, recommended both posterior urethrovesical angle and bladder neck position as quantitative parameters in the ultrasonographic study. The authors proposed a standard method for measuring the retrovesical angle (β) and the pubourethral angle (γ) ( Fig. 13.10 ). The differences between resting and stress bladder neck angles yield the rotational angle, which represents urethral or bladder neck mobility in a similar way as the Q-tip test. No values are defined for normal bladder neck descent or urethral mobility, possibly because of methodologic variations such as patient position, bladder filling, quality of Valsalva maneuver, and measurements of bladder neck position. Whereas several studies have demonstrated that the position of the bladder neck in patients with stress incontinence is lower than those of continent women, an overlap exists between the groups.
