Ultrasound is the standard and first imaging modality used to evaluate pelvic structures. Transabdominal ultrasound provides a global survey of the pelvic structures, whereas transvaginal ultrasound provides a high-resolution technique to accurately assess and characterize pelvic lesions. Occasionally, transrectal or transperineal ultrasound may be performed to evaluate pelvic lesions when transvaginal ultrasound is contraindicated.

Sonohysterography is mainly indicated in menstruating and postmenopausal women with vaginal bleeding, to differentiate between diffuse and focal causes of endometrial thickening and to further characterize focal endometrial lesions. Sonohysterography should be performed in the follicular phase, at day 10 of the cycle, as the endometrium is very thin at this point of the cycle. If performed later, focal endometrial contour irregularities can mimic small polyps or focal areas of endometrial hyperplasia. No anesthesia is required for the procedure. Painkillers may be prescribed 30 min before the examination. Prior to insertion, a 5- or 7-French hysterosonogram catheter must be flushed with saline to rid it of air, which can cause an echogenic artifact. Under due aseptic precautions, the catheter is then inserted through the cervical os into the endometrial canal, and the balloon tip is inflated with 1–2 ml of saline to hold it in place. The speculum is then removed carefully to avoid dislodging the catheter. The vaginal probe is then reinserted and a 20 ml syringe filled with sterile saline is attached to the catheter. Fluid is instilled while the transducer is moved from side to side (cornua to cornua) in a long-axis projection. The uterus is completely surveyed by ultrasound. Adequate visualization of endocervical canal often requires synchronous delicate progressive collapse of the balloon, and fluid instillation into the canal while the catheter is slowly pulled back

Catheter insertion into the endometrial canal may be difficult. Changing the toe of speculum may change the angle of the cervix and often allow successful catheterization. Cervical stenosis may prevent catheterization, which could be circumvented by the use of a cervical dilator or by threading a catheter without a balloon tip over the guide wire into the canal. Before catheter pullout, synchronous delicate progressive collapse of balloon with slow fluid instillation into the canal should be done while the catheter is slowly pulled back.

Common technical pitfalls include the following: introduction of air into the catheter, which produces echogenic artifact and may obscure abnormalities; back flow of the injected saline with non-distension of the uterine cavity; and balloon hyperinflation. Flushing the catheter with saline prior to the procedure may avoid air within the catheter. Backflow can be prevented by gently retracting the inflated balloon to occlude the internal cervical os (Fig. 27.2). Overinflation of the balloon can be avoided by appropriately inflating the balloon to the appropriate level (Fig. 27.3). Complications of sonohysterography are minor and include failure to complete the procedure, pelvic pain, vagal symptoms, nausea, and post-procedure fever.

On unenhanced computed tomography (CT) images, all pelvic soft tissue structures have similar density with complete lack of contrast between individual organs. When imaging the uterus, intravenous contrast is necessary and preferably multiphase imaging must be performed. On contrast-enhanced CT scans, differential enhancement may occasionally be identified, with early and homogeneous enhancement of the uterine corpus and vagina compared with delayed enhancement of the cervix; however, due to the presence of enlarged paracervical venous plexuses, it is extremely difficult to analyze the cervix on CT. The ability of magnetic resonance (MR) imaging to provide unique and superior contrast resolution, along with its multiplanar capability, results in excellent anatomical delineation of pelvic structures. In view of this, MR is the preferred cross-sectional modality to evaluate the normal anatomy, embryological variants, and pathologies of the uterine corpus and cervix.

Mullerian duct anomalies (MDA) are a group of developmental disorders of the internal female genital tract, which represent a continuum of anomalies rather than distinct entities, with few of the complex anomalies having overlapping features. MDAs result from nondevelopment, defective fusion, or failure of resorption of the mullerian ducts [2]. Urinary tract anomalies are associated with MDAs in up to 30 % of cases [3]. Most of these anomalies are clinically asymptomatic; however, if obstruction occurs, patients may present with an abdominal mass, primary amenorrhea, or infertility. MDAs are associated with abnormal myometrial development resulting in weakness and thinning. Other complications include poor reproductive outcome, ectopic pregnancy, and an increased risk for the development of endometriosis. Initial diagnosis may be made at the time of delivery or during evaluation for infertility or recurrent miscarriages. Imaging forms a vital crux in the diagnostic evaluation and most often MDAs are diagnosed using USG and hysterosalpingography. Presently, MR is the modality of choice to evaluate MDAs.

MDAs have been classified by the American Society of Reproductive Medicine based on the anatomic findings (Table 27.1) (Figs. 27.7, 27.8, 27.9, 27.10, 27.11, 27.12, and 27.13) [4, 5]. However, vaginal anomalies are not included in this classification, and various other alternative classification systems have been offered.

Vaginal septal anomalies are classified based on the system developed by Digwani and Falcone (Fig. 27.21) [14]. These are classified into three subtypes – transverse vaginal septum (type I), longitudinal vaginal septum (type II), and stenosis (type III). Transverse vaginal septum represents a vertical fusion defect due to failure of resorption of the tissue between the vaginal plates [15]. Transverse septa are commonly located in the upper vagina in about 46 % of cases; however, these septa can also be identified in the mid (40 %) or lower (14 %) vagina [16]. Patients are usually asymptomatic, presenting only at the onset of menses or later in life due to dyspareunia. MR imaging is used to determine the thickness of the septum and differentiate a high septum from congenital absence of the cervix. Longitudinal vaginal septum occurs either secondary to failure of fusion of the mullerian ducts or incomplete resorption of the vaginal septum [17]. Longitudinal vaginal septa usually occurs in combination with uterine anomalies, mostly uterus didelphys. On MR imaging longitudinal septum appears as a thin, dark T2 signal structure separate from the high T2 signal vaginal mucosa.

Endometrium is the innermost glandular lining of the uterus. The endometrium demonstrates a wide spectrum of normal morphological appearances during the prepubertal years, menarche, and postmenopausal years. Hence, it is pertinent to evaluate and interpret the endometrial appearance in lieu of the patient’s age, stage of the menstrual cycle, coexistent medical illnesses, and drug therapy. At birth, the endometrium appears as a thin line, with or without distension of the endometrial canal [18]. On achieving puberty, the endometrium simulates the adult (premenopausal) appearance. The premenopausal endometrium undergoes cyclical regeneration, measuring 1–4 mm in thickness during menstruation, 5–7 mm during the proliferative phase, up to 11 mm during the late proliferative phase, and 7–16 mm in the secretory phase [19]. In postmenopausal patients, endometrial thickness varies based on the clinical setting, with an upper limit of 4 mm in asymptomatic patients, 5 mm in symptomatic patients, and 8 mm in patients on hormonal therapy. Endometrial thickness is measured on a midsagittal image across the endometrial cavity. On USG, the premenopausal endometrium appears as an echogenic stripe, measured from echogenic border to echogenic border across the endometrial cavity. During the late proliferative phase, the endometrium has a trilayered appearance, which typically disappears 48 h after ovulation. On MR images, the normal premenopausal endometrium appears as a uniform high T2 signal intensity stripe. The normal postmenopausal endometrium is atrophic and appears as a homogeneous smooth endometrium, without focal thickening, measuring less than 5 mm in thickness [20, 21].

Any significant deviation in an established menstrual cycle may be considered as abnormal bleeding. Menstrual irregularities include metrorrhagia, menometrorrhagia, polymenorrhea, oligomenorrhea, menorrhagia, and hypomenorrhea. Histology constitutes the definitive diagnosis; however, imaging plays a key role in screening and identifies patients who require more invasive workup with hysteroscopy or excisions. A wide spectrum of disorders is known to produce abnormal uterine bleeding, and these are typically classified into three subgroups: premenopausal, pregnancy related/peripartum, and postmenopausal (Algorithm 27.2). In this chapter we will discuss in detail the algorithmic approach to pre- and postmenopausal bleeding (Algorithm 27.3 and 27.4) and their various etiologies. Only few peripartum abnormalities will be briefly discussed in this chapter.