It is possible that you have lupus but it can be a difficult disease to disagnose in some cases. Look at www.lupus.org
and there is a lot of good information on symptoms and diagnosis. Check out the criteria for lupus...you should have at least 4 of them to have lupus. Severity of symptoms range from very mild to life threatening.
In answer to your question, lupus can affect your colon and the rest of your digestive tract. It hit mine from top to bottom.
Make sure you write out your symptoms when you see the rheumy.
Mixed connective tissue disease (systemic lupus, scleroderma, polymyositis), Raynauds phenomena, Hypertension, Barrett's esophagus.
Meds: prednisone 5mg, 50mg imuran, Lotrel 40/5mg, maxide 37.5/25mg, folic acid, potassium, aciphex 20mg, multi vitamins.
Maintain your optimism and you can beat the odds.
"Although the world is full of suffering, it is also full of the overcoming of it." Helen Keller