Sounds like my experiences with post Radiation Proctitis and Radiation Enteritis. Big urgency with small loose stools and rank gas. Radiation Proctitis affects the Rectum and in my case bleeding like a period. The solution was getting a Sigmoidoscopy and cauterization of the small veins which worked well. I was prescribed 90 days of Mesalamine enemas for the Enteritis which is intestine inflammation that helped. He also might want to slowly add 20-25 grams of fiber into his diet if not already doing so. I found it kind of ties everything together for a fuller stool. Doesn't help with the urgency but cuts down on the trips. I use Oat Bran with my morning eggs and Raspberries mid-day, and it has helped. At 15 months post radiation and 6 weeks after finishing the Mesalamine I am close to normal. Two prong approach (pun intended). Sometimes ya just gotta go with the gallows humor. Best wishes on his treatment.