justwrong:
If I am correct I believe it stands for Erythrocyte Sedimentation Rate. Basically they take the blood in a test tube and do some stuff to it and see how long it takes for the cells to settle. A high rate is indicative of generalized inflammation. I will admit that although a lot of GI docs like to order this test a lot of docs feel that it is not telling. Meaning some people feel that it indicates inflammation but the inflammation is general marker. Then one has to figure out where it is. C-Reactive protein is also used as an indicator of inflammation. Some people like one or the other and some feel both are useless.
By the way both me ESR and C-reactive protein have almost always been normal for almost all of blood test and I have UC for 20 years.