Before the advent of ultrasound, diagnosis in gynecology was difficult and inaccurate, since it had to be made with the use of bimanual vaginal examination, wherein one would physically feel various pelvic structures and make an attempt to diagnose the pathology. Ultrasound, specifically transabdominal ultrasound (TAS), revolutionised gynecology and for the first time allowed the clinical practitioner to visualise the structures in the pelvis in addition to feeling them bimanually. Today, with the advent of transvaginal ultrasound (TVS), we can not only see the pathology at close range with better resolution, but also simultaneously touch the various structures with the probe and identify whether they are tender, fixed, etc. This interactive component of TVS has further increased the accuracy of diagnosis, giving it in many cases an edge over CT or MRI. Ultrasound for evaluation is also easily available and more affordable. Since TVS accesses many of the pelvic structures at closer range, it also enhances tissue resolution and Doppler evaluation. The addition of Doppler to ultrasound examination, and in particular ‘Power Doppler’ that studies low-velocity flows, helps visualise the presence of flow within tissues and vascular patterns that further enhances the accuracy of diagnosis and also helps in differentiating between pathologies. Images generated by using all these three techniques have been extensively used in the chapters that follow.

In addition to 2D ultrasound (TAS and TVS) and Doppler, 3D ultrasound is also a useful adjunct and is indispensable in the diagnosis of certain conditions like uterine anomalies or the location of intrauterine contraceptive devices (IUCDs). 3D ultrasound has also contributed to accurate volume estimations, as well as reproducibility and storage of data, which is important in the research and study of pathologies. There has also been further progress in ultrasound diagnosis with sonohysterogram (SHG) and gel sonovaginography (GSV), which is resorted to in special cases. All of the above techniques of gynecological ultrasound have been described and employed to identify features and gynecological pathologies in the chapters ahead, and accordingly, images generated using these techniques can be found across various chapters of this book.