Can a ct scan detect pregnancy when having a ct scan for appendix? how early cam it detect a pregnancy ?

Shouldn't be used: Nearly all facilities will test for pregnancy with a blood test prior to performing a ct scan on a women of childbearing age due to potentially harmful radiation effects to a developing embryo or fetus. Whether they told you or not they probably checked at the time you were evaluated for appendicitis. It is rare to see a fetus on a ct scan because of this, but sometimes is seen in emergency scan.

Inappropriate test: Ionizing radiation will cause damage to dna and fetal tissue and children are most susceptible to the damage. There are many options to confirm or evaluate for pregnancy - most commonly a urine test, and fetal viability can be evaluated with ultrasound.