The designation "blood trace in urine" indicates that a small amount of blood is present in urine, according to WebMD. The presence of blood in urine is called hematuria, and it can result from a variety of infections or diseases.
A large amount of blood in urine makes the urine look light pink or tea-colored, but sometimes the presence of blood is only noted when a doctor sees red blood cells in the urine after looking at a sample through a microscope, notes WebMD. Either condition indicates a potential bladder infection or possibly some problem with the kidneys or prostate. Certain medications can also caused blood to appear in the urine. People with hematuria may not experience other symptoms.
Kidney and bladder stones, an enlarged prostate and medicines, such as aspirin, penicillin and heparin, may cause a trace of blood in the urine, states WebMD. Vigorous exercise can bring on hematuria. A more severe cause of hematuria is a tumor in the kidney or prostate or an injury to the kidney. Doctors typically order a urine sample to get a closer look at the blood and its cause. More often than not, hematuria resolves itself and does not require treatment unless the condition is severe.