He may have hemorrhoids or possible anal fissures (which are like tears in the anal opening)
Bright red blood usually suggest that the blood is coming from the lower part of the GI tract (large bowel or rectum). Which most often is due to hemorrhoids or anal fissures, which is a small tear. I don't know how much blood there was. However if there is a lot say at least between a teaspoon to a tablespoon, then he should be seen.
Since he generally is constipated, once the problem is eliminated, then most often the bleeding will stop etc. Which an increase in fiber and more fluid in take (water is best) which a combination of both help soften stool and allows for stool to pass easier. If this doesn't help, then he should follow up with his doctor.
As far as the current bleeding, if you can look around the anal area to see if you can any tears or even hemorrhoid, or if you determine there is a lot of blood, then do have him seen tonight.
Below are two excellent sites that explain about Hemorrhoids as well and additional information on what can cause them along with treatment and prevention.
Hope this helps, If you need anything else please feel free to ask. If you found this helpful don't forget to click the *ACCEPT* button and please take a moment to leave me *POSITIVE* feedback.
