What Causes Severe Pain Between Scrotum And Anus After Bladder Scope?

In 2011, my husband had treatment for prostate cancer, brachytherapy and radiation. Last September,he had a kidney stone blocking the tube between his kidney and bladder and his urologist did a scope and used a laser to blast it. In late October he started having severe pain between his scrotum and anus. His urologist did several scopes since, scraping away dead tissue from the prostate and widening the urethra. He has very little appetite, has lost about 40 lbs since March, is very weak and his hands shake a lot. He also twitches a lot in his sleep. He is on a low dosage of dilaudid for pain. He has seen the Dr. who did his treatments and a gastroenterologist. Currently he has a catheter which has been in place since early June. He is scheduled for another bladder scope July 30 and a bowel scope Aug. 7. The Drs. seem to think the pain is from nerve damage from the radiation. Why would the pain start that long after the treatment? It only started after he had the kidney stone blasted, could there have been some damage done during the scope?