Neil, when we see blood in the stool with diarrhea this is a sign of inflammation in the large intestines (colon). In a young dog like Reggie this can be caused by many different medical conditions. I will not be able to pinpoint the exact underlying cause without a hands-on examination and some testing, I am sorry. But, common causes are dietary indiscretion, parasites, ingestion of a foreign body, infections, or even part of a systemic disease to name a few causes. To determine the exact underlying cause he will need to see your family veterinarian and a fecal analysis as an initial screening test. In the meantime, this is what you can do:
1- Do not give things like Pepto Bismol or Imodium.
2- Change his diet to rice (75%) and boiled boneless chicken or ground beef (25%) until the stool is back to normal then wean him back into his regular diet.
3- Supplement with a probiotic, these are friendly bacteria that help with regularity and inflammation. You can buy this over the counter in any pet store.
4- Follow up with your family veterinarian for a hands on examination.
My goal is to provide you with excellent service. If you have any follow-up questions don't hesitate to ask. If finished, please take a moment to rate my service it is how I get compensated. See you again soon!