Does anybody know how much cortisone (or hydrocortisone) leaks out
into the body from a cortenema containing 100 mg cortisone, or has
other information that can be useful to me? I suddenly got a bad back
after radiation and hormone treatment for prostate cancer. It
misteriously got better after a cortenema given to me because of a
suspicion that a rectal bleeding occurred because of inflammation
caused by the radiation treatment sonewhere in or near the large
intestine.

Virtually all of the 100 mg will be absorbed. Corticosteroids inhibit
inflammation for both intra and extra cellular release of inflammatory
signals(whereas normal antiinflammatories inhibit only intracellular).
Intracellular inhibitions include prostanoids (like prostaglandin);
extracellular inhibitions include leukotrienes. Corticosteroid
injections are actually a normal treatment for back pain.