My son has had diarrhea and fever we saw doctors and all tests were done now no fever but still diarrhea with blood in stool for more than four days?

To vague for comment: Diarrhea is a common problem in kids occurring 2-3X/yr up to age 5 in most. The common origin is a family of gut viruses but bacteria or food reactions can also be involved. You say you saw docs but give no test results or past treatments. We can provide more analyses or information when you provide more background information.