Dog digestive problems

Question
I have a 14 year old Chinese Crested Hairless dog that has a constant case of diaherra.  It even has blood in it sometimes.  He has had trouble walking and standing for some time now, which I assume is due to his age and hip problems.  I have been giving him canine joint medicine when his legs seem to cause him a lot of problem.  He is still eating his regular food, however he just lays around all day and wants to sleep.  Is there anything that I can do to help him get over his digestive problem?  

Answer
He should be eating a hypoallergenic, all-natural diet.  I would recommend Nature's Recipe Venison or Fish as a start which is easily digestible and designed for food allergies.  In addition, you can add plain yogurt to his food and digestive enzymes such as those made by Dancing Paws www.dancingpaws.com Shake N Zyme.   As far as the joint problems, you can give him 500 mg of Glucosamine twice a day in addition to MSM, which is a natural anti-inflammatory, at a dose of 50 mg twice a day.  I would highly recommend starting him on Cholodin as well or a B complex vitamin with Choline in it (20 mg a day).