PLAIN FILM OF THE ABDOMEN

The flat plate of the abdomen, taken as a scout film for intravenous pyelogram (IVP) or as a plain radiograph, can screen for urinary calculi. In addition, it may also reveal pelvic masses, bony lesions, and calculi in suburethral diverticula.

INTRAVENOUS AND RETROGRADE PYELOGRAPHY

Despite the emergence of newer imaging techniques, IVP is still frequently used to evaluate the urinary tract (Fig. 10-1). IVP is safe, inexpensive, and widely available, and it provides information about the anatomy of the collecting system and functional status of the glomerular filtration apparatus. Computed tomographic (CT) IVP is gradually replacing conventional IVP because it gives more precise information about renal anatomy and function. 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. IVP, with delayed films and tomography, is also useful to help diagnose certain uncommon conditions, such as ectopic ureter and ureterovaginal fistula. Although IVP is safe, it is an invasive procedure and exposes patients to injection of iodine dye and to radiation; it is contraindicated in pregnant women or those with allergy to iodinated contrast media, renal insufficiency, and congestive heart failure. Because of these disadvantages, abdominal and Doppler ultrasounds have been used as a noninvasive and less expensive alternative to diagnose ureteral obstruction.

Figure 10-1 Intravenous pyelogram showing duplication of the collecting system of the left kidney.

If the pelvicaliceal or ureteric anatomy is not adequately visualized with IVP, or if there is a contraindication to IVP, an alternative approach is to perform a retrograde pyelogram, which is especially useful if there is a coexisting indication for cystoscopy. In retrograde pyelogram, the contrast medium is injected into the upper urinary tract through a cone-tipped catheter placed at cystoscopy under fluoroscopic guidance (Fig. 10-2). This approach is associated with a higher infection rate than antegrade pyelography and may be contraindicated in women with known allergic reaction to contrast media or very 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.

Figure 10-2 Ureteral catheter used to perform retrograde pyelography.

Antegrade pyelography can provide excellent opacification of the renal collecting system. 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 of 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. 10-3). 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.

Figure 10-3 Retrograde contrast instillation into the bladder via a urethral catheter demonstrating a vesicovaginal fistula.

To determine whether a cystotomy or fistula repair has healed, the bladder is filled slowly with contrast medium and then 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

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. VCUG is also used to investigate suspected bladder fistula or suburethral diverticula (Fig. 10-4) and to evaluate the integrity of the bladder or urethra after fistula or diverticula surgery. Because of recent advances, ultrasound and magnetic resonance imaging (MRI) technology have replaced VCUG as the primary imaging modality in diagnosing many of these conditions.

Figure 10-4 Voiding cystourethrogram demonstrating three small proximal suburethral diverticula (arrow).

POSITIVE-PRESSURE URETHROGRAPHY

Positive-pressure urethrography was first described and used by Davis and Cian in 1956 to evaluate the female urethra. Today, the primary indication for this diagnostic test is to search for possible suburethral diverticula not visualized on VCUG. The 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. 10-5). This radiologic test is often performed in conjunction with VCUG to maximize the 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.

Figure 10-5 Positive-pressure urethrogram showing a large, multiloculated suburethral diverticulum.

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 gold 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.

ULTRASOUND

After the introduction of real-time technology in the 1980s, ultrasound has been widely applied and has sometimes replaced radiography in the evaluation of pelvic floor disorders. It has the advantages of noninvasiveness, reproducibility, nonradiation exposure, and less expense. With use of high-resolution transducers, pelvic organs can be demonstrated clearly on ultrasonography. Moreover, three-dimensional technology with simultaneous axial, transverse, and coronal views of pelvic organs clearly displays the spatial orientation of the female lower urinary tract. Both color and power Doppler scanning not only can reveal the vascular flows of pelvic organs, but also can demonstrate the urinary flow. Color Doppler ultrasound analyzes the frequency shift of flow velocity information, whereas power Doppler technology uses the amplitude component of received signals to quantify the number of moving particles.

Many approaches have been proposed for the evaluation of the lower urinary tract by ultrasound. These include transabdominal, transvaginal, transrectal, perineal (or translabial), and introital approaches. Because the lower urinary tract can be shaded by the acoustic shadow of the pubic symphysis, the transabdominal approach is used mainly to visualize the kidneys and pelvic organs, and for simple office measurement of bladder urine volume.

Basic Procedure of Perineal Ultrasound

For dynamic assessment, the transvaginal 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) or introital approaches are used currently. The differences between perineal (translabial) and introital approaches are the site where the transducer is placed and the probe used in the ultrasonographic scanning: perineal (translabial) ultrasound uses a linear- or curved-array convex probe with frequency between 3.5 and 5 MHz; introital ultrasound uses a sector endovaginal probe with frequency between 5 and 7.5 MHz. The transducer is placed on the perineum in the perineal (translabial) approach; it is positioned between the labia minora just underneath the external urethral orifice in the introital approach. Both approaches have been proven to be devoid of potential morphologic artifacts resulting from distortion of the bladder neck or urethra.

The information that should be obtained during ultrasonographic evaluation of the female lower urinary tract is shown in Box 10-1. Some disagreement exists regarding the optimal orientation of images. Some authors prefer an orientation as in conventional transvaginal ultrasound. However, others recommend showing superior structures above, inferior structures below, anterior structures on the right, and posterior structures on the left.