Standard requirements for two-dimensional (2D) translabial or transperineal ultrasound (TPUS) of the pelvic floor include a B-mode ultrasound machine with cine-loop function, convex transducers of 3–6 MHz, and a field of view of at least 70°. A midsagittal view is obtained by placing a transducer on the perineum [2, 6, 7] (Fig. 13.1). For hygienic reasons the transducer is covered with a glove, condom, or thin plastic wrap. Powdered gloves can impair imaging quality owing to reverberations and should be avoided. Sterilization (as for vaginal or endorectal transducers) is considered unnecessary; mechanical cleaning and alcoholic wipes can be used for disinfection. The patient lies in the dorsal lithotomy position with the hips flexed and slightly abducted. Pelvic tilt can be improved by bringing the heels closer to the buttocks and by moving the hips towards the heels. The patient is asked to void before the examination in order to allow a full Valsalva maneuver, but bowel emptying is not mandatory. A full rectum can impair diagnostic accuracy, and at times the assessment has to be repeated after bowel emptying. Parting of the labia can improve image quality, especially if the vulva is hypertrophic or hirsute. Vaginal scar tissue and modern mesh implants may impair visibility. Obesity is rarely a problem. Imaging is performed at rest, maximal Valsalva maneuver, and maximal pelvic floor muscle contraction (PFMC). Pelvic floor ultrasound provides both static and dynamic imaging and allows anatomical and functional assessment of the different compartments. It is currently used in specialized urogynecology centers, but can be implemented more widely in any outpatient clinical setting without any discomfort to the patient. An important advantage of this methodology in the context of pelvic pain is that it is noninvasive and more widely acceptable for the patient.

The standard midsagittal view includes from anterior to posterior: t he symphysis pubis with the urethra and bladder neck immediately dorsally, vagina and cervix medially and rectum and anal canal posteriorly (Fig. 13.1). Further posteriorly to the anorectal junction, the central portion of the levator plate (or the puborectalis sling) is seen as a hyperechoic structure [2]. Parasagittal or transverse views allow additional information, such as visualization of the urethra, puborectalis muscle attachment, and depiction of mesh implants. Confounders that block the view may be as a result of shadowing from vaginal prolapse, the pubic bone, or a full rectum, particularly in the presence of a rectocele obscuring the posterior compartment, or the vaginal apex.

3D and 4D TPUS is performed with 3D transabdominal probes developed for obstetric imaging (such as RAB 8-4, GE Healthcare Ultrasound, Milwaukee, WI, USA; AVV 531, Hitachi Medical Systems, Tokyo, Japan; V 8-4, Philips Ultrasound, Bothell, WA, USA; 3D 4–7 EK, Medison, Seoul, South Korea). These transducers combine an electronic curved array 4–8 MHz with mechanical sector technology, which allows a fast sweep through the field of view (Fig. 13.2). This technique enables the creation of tomographic multislice imaging in a chosen plane giving a picture similar to CT scanning (without any radiation), called tomographic ultrasound imaging (TUI) (Fig. 13.3). TUI enables assessment of the entire puborectalis muscle and its attachment to the pubic rami, to measure the diameter and area of the levator hiatus, and to determine the degree of hiatal distension on Valsalva maneuver [8]. 4D imaging allows real-time acquisition of volume ultrasound data, which can be visualized in orthogonal planes or rendered volumes. The 3D data is archived as a cine loop that allows maneuvers such as Valsalva and PFMC. The methodology also allows data storage and offline analysis with the help of dedicated software (4D view, GE Healthcare Ultrasound, Milwaukee, WI, USA, and others) [9].

4D ultrasound imaging of the pelvic floor has significant ly enhanced the clinical approach to complex urogynecological conditions, and is rapidly becoming more available in tertiary facilities. Its main advantages are ease of use, availability within the gynecological clinic, lack of radiation or contrast media, and performance by the patient’s clinician, all of which make it superior to MRI [10]. It is particularly useful for assessing the dynamic function of the pelvic floor complex, and can provide an enhanced view of soft tissues, particularly the levator ani complex [2]. Furthermore, ultrasound real-time imaging allows the operator to identify and control for common confounders in the clinical examination, such as bladder and rectal filling [11], suboptimal performance of Valsalva maneuver, often seen as levator muscle co-activation [12], and duration of Valsalva maneuver [11]. In order to enhance exam yield it is recommended to ensure bladder (and possibly rectal) emptying, a sufficiently long Valsalva (at least 5 s) a maximal Valsalva effort, and relaxation of the levator ani [11]. Ultrasound allows visual biofeedback, which greatly facilitates achieving an adequate Valsalva maneuver and PFMC.

While in the past MRI was considered the standard in vestigation for detecting PFM injuries resulting from vaginal birth, high-resolution 3D and 4D ultrasound i mages can be equally accurate in demonstrating anatomical and functional defects which can result in prolapse and incontinence. Some of these defects may be missed during a clinical examination, which could lead to suboptimal surgical repair and need for repeat surgical procedures [13]. Translabial ultrasound, especially 4D real-time imaging, has the major advantage of providing a global view of the entire pelvic floor, from the symphysis to the anorectum, and includes the lower aspects of the levator ani muscle. As a result, the modality is optimally suited for interdisciplinary assessment and communication [7].

Transvaginal ultrasound (TVUS) is performed in a position similar to TPUS. There are several available probes: electronic biplanar 5–12 MHz, with high frequency (9–16 MHz), mechanical probes rotating 360°, or radial electronic probes (type 8848, B-K Medical, Herlev, type 2050, B-K Medical, type AR 54 AW, 5–10 MHz, Hitachi Medical Systems Denmark) [1]. Whichever probe is used, it is important to keep it stable avoiding excessive pressure on adjacent structures, which may distort anatomy. The choice of this modality as opposed to TPUS mentioned above will be dependent on operator experience and preference or specific indications as described in Table 13.2.

Biplanar electronic probes allow 2D sagittal and axial sectional imaging of the anterior and posterior compartments. As for TPUS, imaging is performed at rest, maximal Valsalva, and PFMC. This methodology also allows the use of color Doppler to image the v ascular pattern of pelvic floor structures [1]. 3D images may be obtained by adding an 8848 transducer to the external 180° rotation mover allowing sagittal, axial, and coronal and any desired oblique sectional images to be obtained [1]. The radial electronic probe and the rotational mechanical probe allow a 360° of the pelvic floor. A 3D volume can be acquired for real-time manipulation, or archiving for offline analysis with dedicated software.

Endoanal ultrasound (EAUS) is p erform ed with a high multifrequency, 360° rotational mechanical probe or a radial electronic probe, as described for TVUS. The patient is placed in a dorsal lithotomy, left lateral, or prone position. In all situations, the transducer is rotated so that the anterior aspect of the anal canal is superior at the 12 o’clock position. 3D acquisition is achieved with the mechanical rotational transducer allowing a thorough investigation, volume manipulation, and measurements in any plane [14]. This methodology is more widely described in Chap. 12.