Before hida scan i fasted for 20 hrs could this throw the results off?

Possible slow EF: Normally 4-8 hours is amount of time for fasting prior to hida study. Prolonged fasting can interfere with results of study and demonstrate cholestasis, slow emptying of gall bladder (decreased ejection fraction of gall bladder). This has been shown in patients being fed by intravenous and not oral for prolonged periods of time.

Generally fasting: Less than 24 hours is ok for hida scan. However, the risk is inability to fill the gallbladder with radioactive bile. Fasting cannot make what would have been an abnormal test normal. So, if your test result was normal, there is nothing to worry about. If your test was abnormal or borderline, please let your doctor know about the fasting.

Not likely: Usually we say dont fast more than 24 hrs. So in general 20 hrs would probably be ok...We would not want someone to fast much longer then that. However, if someone has fasted longer than 24 hrs, a medicine can be given before the study...So that we dont have problems caused by this.