How risky are CT Scans and colonoscopy?

Some questions. Unbiased view and any person experience would really be helpful:

(1) How risky are CT Scans? Concerned about radiation
(2) How risky is colonoscopy?


I'm 39 years old male, battling with parasite problems for years.

I had 3 ultrasound done in the last 3 months, the observations are:
(1) Stable echogenic mass in the liver compatible with an hemagioma
(2) Stable benign appearing cyst in the liver
(3) Persistent fluid in the right lower quadrant again unusual in this male patient and with mildly enlarged mesenteric lymph nodes raises the possibility of a chronic bowel inflammatory process in the appropriate clinical setting

Recommendation:
Follow up of the persistent fluid in the right lower quadrant and now with mesenteric lymph nodes with CT scan may be helpful.