DO NOT use cholloidal silver in the colon because you risk your colon flora which regulates your immune response! If you do it and destroy the flora which are protected inside biofilms, anything which is passing through your colon can setup home and implant into your colon. This might not be a positive effect because of the large quanitity of bacteria, yeasts and fungi, viruses etc which are passing through the colon. I did have a similar idea a long time back but not using Colloidal Silver and I had 2nd thoughts about doing it and did not proceed.
It would be better to take it by mouth and keep it under the tongue and do that repeatedly many times a day to raise the intake to a high level due to the small amount that can be held in the mouth.
If you can get some down the urethra then go ahead but I would not fancy doing that but your situation might make that appealing because it is a little more direct. I do not see how you would accomplish that because it is designed not to allow fluids in only urine out. Bacteria are something different. I cannot give any instructions on how to do that without causing damage.