Definition. The erythrocyte sedimentation rate (ESR), or sedimentation rate (sed rate), is a measure of the settling of red blood cells in a tube of blood during one hour. The rate is an indication of inflammation and increases in many diseases.
Having blood in the stool can be the result of a wide variety of conditions, such as hemorrhoids, diverticula, inflammatory bowel disease, rectal prolapse, colorectal cancer, rectal abscesses, intestinal infections, peptic ulcer, intestinal polyps, constipation or anal fissures.
Black stools can be due to iron supplements or excess iron in the diet. The most serious cause of black stools is bleeding in the GI tract, due to ulcers or some other cause. If the stool is black due to blood, it usually has a tarry feel. If there is just a black color, most likely it is not blood.