Abd ct w/ contrast 4mm low-attenuation lesion right hepatic lobe present likely a benign cyst or hemangioma too small to characterize need follow up?

This is not uncommon: Benign lesions like the one/s you have are quite frequently seen when CT scan of the abdomen is done for any reason.Your test ordering doctor, then has to help you sort it out. We start by asking: why was the CT scan done in the first place? What was the doctor looking for in the abdomen/liver? Follow up CT scan is often recommended by radiologist but it is frequently not necessary, but it depends

Not to worry: At your age an incidentaloma like this shouldn't raise eyebrows. That said, it is hard to argue against a liver ultrasound in a year just to make you feel better. The likelihood that is a waste of money is huge, but if it helps you to sleep better, so be it.