Many patients may not know what is meant by pelvic floor muscle contraction . It is better to phrase it in a more familiar way such as “Please do a Kegel exercise contraction,” or “Pretend you are holding your urine or gas.” This maneuver shows whether or not the patient is discoordinated. Generally, a normal patient has a strong resting tone and the levator lifts slightly; a patient who has weak pelvic floor can move the levator plate to a longer distance but cannot maintain a normal woman’s resting position (Fig. 3.2) [2].

When the patient is asked to perform Valsalva the instructions could state, “Bear down as if you are trying to have a bowel movement.” It is important that this is the last thing you would ask the patient to do during a dynamic ultrasonography because if she has gas in the upper rectum, it may move down and obscure the 2D/3D images you intend to obtain. If this happens, you can ask the patient to perform Valsalva again and, with the anterior movement of the levator plate, the gas and prolapse may move up cephalad. Important information can be obtained with Valsalva. Evacuation proctography used to be the gold standard to diagnose posterior compartment prolapse. A prospective study in 75 women has shown moderate to good agreement between 3D transperineal ultrasound and evacuation proctography to detect enterocele and rectocele (Fig. 3.3a). The advantage of 2D transperineal ultrasound is the view in the midsagittal plane. In this view one can visualize descent of an enterocele, the movement of the anterior rectal wall to detect a rectocele (Fig. 3.3b, c). Enterocele or, most commonly, sigmoidocele (Fig. 3.4), cystocele (Fig. 3.5), or multicompartmental defects may come to view with Valsalva maneuver. Dynamic imaging with Valsalva shows the movement of slings and meshes and may show the point of defects above, below or lateral to the mesh (Figs. 3.6 and 3.7).

3D/4D ultrasound has increased public interest in the pelvic floor tremendously. The superficial axial plane faces the puborectalis portion of the levator ani, and all the levator subdivisions are better imaged by endocavitary transducers such as BK 2052 or BK 8838. However, endocavitary transducers impede Valsalva maneuver. Although the quality of perineal pelvic floor 3D/4D ultrasound images is reasonable, the end-fire endocavitary transducers used introitally have much higher resolution and may give better images.

If you have a BK ultrasound machine, the curved array transducer is capable of free hand acquisition of 3D volumes (Figs. 3.8 and 3.9). However, freehand acquisition with BK Curved Array 8802 (BK Ultrasound, Analogic, Peabody, MA, USA) is advisable only if you do not possess a BK 2052 or BK 8838. Performing freehand acquisition of a pelvic floor 3D volume takes, first, considerable skill to move the transducer at a constant speed as it sweeps radially from the patient’s right to left. Second, the acquired 3D volume is not repeatable or reliable for measurement purposes. Third, and most importantly, if you have endocavitary 16 MHz transducers at your disposal, which obtain automatic high-resolution views of the levator ani muscles (LAM) , it obviates the need for freehand perineal pelvic floor ultrasound acquisition.

The most commonly published data comes from GE Healthcare (Chicago, IL, USA) machines. Philips (Royal Philips, Amsterdam, The Netherlands), Hitachi (Hitachi Ltd., Tokyo, Japan), and others make similar or superior machines. Halo Medical Technologies (Wilmington, DE, USA) has recently introduced a low priced pelvic floor ultrasound machine. Halo does not obtain 3D images, rather video clips that can be played. GE’s 4D View is available for offline analysis and use with 4D ultrasound volumes obtained using GE’s Voluson series systems. The cheapest and most easily available system is the GE Voluson e or i (Fig. 3.10). Despite its compact size the system is very capable when used with the GE RAB4-8-RS transducer (Fig. 3.11). The systems were developed and designed to visualize surface structures of the fetus and adapted for pelvic floor imaging. GE Kretz 4D view allows manipulation of image characteristics and output of stills, cine loops, and rotational volumes in bitmap and AVI format. Slightly higher resolutions can be obtained if the GE endocavitary RIC5-9W-RS is used on the perineum (Fig. 3.12). The characteristics of these transducers are shown in Table 3.1.

The GE transducer is placed between the labia majora and the 2D image as outlined above is displayed on the screen. Depending on the setting of your machine, image orientation may be different. We place the ultrasound machine to the patient’s left and operate the probe with the left hand (Fig. 3.13), leaving the right hand available for running the console (Fig. 3.14). Once you have the appropriate 2D view, maximize the angle of acquisition to 75–85° and proceed with 3D imaging (Fig. 3.15). During or after acquisition of volumes it is possible to process imaging information into slices of predetermined number and spacing, reminiscent of computer tomography. This technique has been termed tomographic ultrasound imaging (TUI) by manufacturers. The combination of true 4D (volume cine loop) capability and TUI allows simultaneous observation of the effect of maneuvers. Using this methodology, the minimal levator hiatus (MLH), defined in the midsagittal plane as the shortest line between the posterior surface of the symphysis pubis and the levator plate, is the plane of reference, with 2.5 mm steps recorded from 5 mm below this plane to 12.5 mm above.

Fig. 3.16a reveals the obtained 3D image following the initial 2D image, using a symmetric rendered volume, of about 1.5–2.5 cm thickness, rendered caudal to cranial [10]. After capturing the 3D image, the volumes can be stored on a drive and assessed offline. The offline post-processing is done with special software that allows rotation of the volume, thick and thin slicing, and multiple measurements. During the post-processing of volumes the 3D static images are rotated to be displayed in a symmetric orientation in the three orthogonal planes: coronal, sagittal, and transverse planes. A cursor dot (colored green in Fig 3.16a) is located in corresponding positions in all three orthogonal planes. A cursor dot allows for the exact position of an anatomical structure to be identified simultaneously in the three orthogonal planes. The way to rotate the captured volume is described in four steps:

The bar with the green topline in the 2D image is in the plane of the minimal hiatal dimensions after the image has been postprocessed. The visualized landmarks are: pubic bone on both sides, urethra at 12 o’clock position, vagina in the middle, anal canal at 6 o’clock position, LAM on the left and right side of the vagina, surrounding the anal canal (Fig. 3.16b–d).

The software is available on the GE machines and also through the “Voluson Club” for Voluson ultrasound machine purchasers. Separate licenses for the software are expensive and not available to those who do not have a machine.