Most scans carried out for a gynaecological indication or in early pregnancy (less than 10 weeks) are carried out using a vaginal probe and we are often asked why this is the case – why not do them abdominally and avoid an internal examination?
The reason is that the ultrasound transducer on the end of a vaginal probe is closer to the “area of interest” or the part we need to look at. As a result we can use high frequency ultrasound which is normally absorbed if it has to travel through too many tissues. The advantage of high frequency ultrasound is that is give much better image resolution. To put this in context we can see the heartbeat of an embryo about 2 weeks earlier vaginally than abdominally. Similarly all the studies on classifying the lining of the womb or ovarian cysts have been based on high resolution vaginal ultrasound, and so using abdominal scanning when looking at possible gynaecological problems is not the best thing to do and may well give quite different results. Carrying out a vaginal ultrasound scan is also a dynamic process and allows the examiner to look at the mobility and tenderness of the organs in the pelvis – both of which are factors when considering a possible diagnosis. An interesting article on this can be read here: http://www.ncbi.nlm.nih.gov/pubmed?term=testa%20timmerman%20dynamic%20ultrasound