Bruce's type of medical condition can be brought on by several factors given his age. The bladder blockage could have been due to an enlarged prostrate (very common in men in their late 50s). The intestinal blockage could have been due to chronic diverticulosis (also common in older men and women). Without enough fluids and fiber (and access to an enema) he could easily become blocked. I don't know if Bruce had these type of chronic conditions which led to his health problems on the island, but I think it is a fair possibility.
I too was very sorry to see Bruce leave and felt for him. He was in terrible pain, but what a stoic soul he is. It does make you wonder what gives a man like him such grit, when some of the younger men like Osten who are in perfect health and physical condition, balk at even the slightest discomfort, whine continually, and quit the competition. It doesn't seem fair that this poor guy, who is such a competitor (even in the throes of ungodly pain, he didn't want to leave the game), has to leave and Mr. Whine-a-lot Shane gets to stay.