What can a pelvic ct scan show that an ultrasound doesnt?

CT show more.: An ultrasound study is heavily dependent on the skills of the technologist. The us also does not typically see everything in the pelvis, particularly with regard to the bowels (colon, rectum, appendix) and does not see structures outside of the uterus or ovaries well such as lymph nodes. A ct study also can show the bones whereas this is typically not possible with us.

A few things: Better look at bowel, enlarged lymph nodes, areas of infection, and all the bones. Also better characterizes many abnormalities seen on ultrasound.