Can pheochromocytomas sometimes be too small to see on CT scan of abdomen? How long would it take for them to grow big enough to be seen?

Imaging. CT scan limit for detection is at 1 cm. So yes, could be too small to detect on imaging. Your doc can detect it with other techniques, such as blood labs, urine testing. Okay to ask to see a specialist, endocrinologist for help with diagnosis. Be well.