Mucus is frequently found in urine sediments examined under a microscope. Mucus is high in protein and can come from all parts of the urinary tract (components of the urinary system). Its role is to protect against bacterial infections. In most cases, the presence of mucus is of no clinical significance. Other parameters (blood, leukocytes, bacteria, casts) can be used to link the presence of mucus to a more specific cause, such as urinary tract irritation or inflammation.