Blood with stools

Hi - this morning my husband bad some blood with his stools. Now, he's had that before, not to often, maybe once or twice a year, but no other upfront, obvious symptoms. Right now, all of us are dealing with some sort of "bug" that's going around, but other than that, nothing. He is 45yrs. old, basically in average health, not overweight (he could probably stand to loose about 10lbs.). He did experience pain at the anus opening as it came out, but not up in the intestinal area. He thinks he must have passed a stone, I don't know. Like I said, he's had this before, as far back as 1998, on occassion. Sometimes it's just a little blood, other times, it's a bit more. Could someone please tell me what you think this is, I have a tendency to become panicky with things like this! Thank you! Miranda