Pelvic vs stomach ultrasound? 10 points?

Nope, two different exams. The pelvic ultrasound you had would have only looked at your prostate (possibly) and bladder. An abdominal ultrasound looks at the abdominal organs housed under your rib cage - pancreas, liver, both kidneys, gall bladder, and spleen. You aren't allowed to eat/drink 8 hours prior because it causes your gall bladder to contract (which means it wouldn't be seen on ultrasound) and causes air in your stomach/bowel which obscures ultrasound.