Similarly, manipulation of the 3D volume obtained with transducers such as the 2052 and the 8838 probes of the BK Ultrasound line of machines can also be done in the axial, sagittal, and coronal planes (see Fig. 11.2). Manipulation of the 3D volume in the sagittal plane helps to ascertain the exact location of the UBA in relation to the urethral length, while manipulation in the axial plane gives valuable information about the periurethral distribution of the UBA.

The ultrasound signal produced by the UBAs varies, depending on the makeup of the agent. Collagen-based UBAs vary between hypoechoic, isoechoic, and hyperechoic [22] in echodensity, whereas the signal from a calcium-based agent will produce a hyperechoic structure on the image (see Fig. 11.1). Bulking deposits vary in size and shape and also vary in their symmetry of periurethral distribution. Because of the irregular and varying shape UBAs take after injection; three-dimensional ultrasound is ideal for imaging as opposed to a purely cross-sectional modality [22].

While superior images can be obtained with specialty transducers, UBAs can be imaged well with transducers commonly found in most ultrasound departments. It is reasonable to assume that a sonographer may inadvertently stumble upon urethral bulking during a pelvic or renal sonogram. While the bladder is seen on both transabdominal pelvic and renal sonograms, the urethra is not routinely imaged on either study. UBAs can mimic a bladder stone when imaged transabdominally with a convex transducer (Fig. 11.3). If a questionable echogenic structure is seen transabdominally, additional imaging may be ordered. Given that ultrasound is the method of choice for imaging UBAs, a few questions about the patient’s past medical history and few additional sonogram images may spare the patient the expense, inconvenience, and anxiety of additional imaging with another modality.

Apart from pelvic floor specialists, few sonographers may have heard of UBAs or procedures. If sonographers are knowledgeable about UBAs and the images they produce, we have the tools available to help avoid unnecessary expense and CT radiation exposure to the patient. The same curved transducer used for transabdominal pelvic and renal sonograms can be used perineally to image the urethra. The patient should be scanned in the lithotomy position as when scanning transvaginally. The transducer should be prepped in a similar fashion as a traditional endovaginal transducer. An ample amount of gel should be dispensed on the transducer and then covered with a transducer cover or glove. It is important to ensure that there are no air pockets between the cover and the transducer. After applying gel on top of the cover, the transducer should be placed on the perineum. While tissue contact is required, care should be taken to avoid applying too much pressure [23]. The pubic symphysis, urethra, vagina, and rectum can all been seen clearly. The abdominal probes used for perineal pelvic floor imaging display the image on the screen as designed for an abdominal probe (Fig. 11.4) [24], not the anatomically correct orientation for pelvic floor imaging. Most experts in pelvic floor imaging prefer that the perineal image be displayed in a nontraditional orientation mainly because the preset on the ultrasound machines are meant to image the abdominal wall. The pelvic floor ultrasound image obtained by a wide array abdominal probe is therefore inverted and reversed (Fig. 11.5), as if the patient is standing, and the images are obtained from the left sagittal plane. We take the trouble of righting the image to the anatomically correct position. This orientation represents the female pelvis in the functional standing position (Fig. 11.6). This is considered our standard orientation in pelvic floor ultrasound imaging.

End-firing vaginal probes typically used to image the uterus and ovaries can also be used to image the urethra and the bladder neck. Unfortunately, the urethra is typically bypassed completely as the pelvic organs are imaged. The transducer and patient should be prepped as usual for traditional endovaginal sonogram. On insertion, the transducer should be angled anteriorly to clearly view the urethra and UBA (Fig. 11.7).