The body responds to an invasion of germs by mobilizing blood leukocytes which crowd into the infested tissue area. The leukocytes carry antibodies, and some have the ability to engulf germs. In the ensuing conflict leukocytes as well as germs and some tissue cells are destroyed.
In mild infections the remains of the germs are carried away by the blood and lymph to be disposed of in other parts of the body. But in a severe infection the debris of cells and germs becomes pus, which may be eliminated as a purulent discharge from one of the body's openings, or may form a pus-filled abscess if the infection occurs deep in the body's tissues. Pus is a liquid waste product which contains many pus cells - leukocytes expended in the conflict with germs.
Purulent Discharge From the Bowel. In the later stages of dysentery and in severe colitis, pus is often passed with the stools. Cancers of the lower colon or rectum may destroy so much tissue that germs invade the area, producing pus.
Purulent Discharge From the Ears. Infection of the middle ear (otitis media) is usually preceded by infection of the pharynx, as in the common cold or sore throat. The infection gains access to the middle ear through the auditory tube, which runs between the pharynx and the middle ear. As the infection develops in the middle ear, pus is produced. Normally pressure building up within the middle ear, as when a person goes from a lower to a higher altitude, is relieved through the auditory tube. But in otitis media, the auditory tube is already inflamed and swollen so that the pus, as it develops, cannot escape by this route. Pressure develops as the pus accumulates and the patient suffers from earache. If the condition goes untreated, the eardrum may burst, permitting the pus to escape to the outside through the external auditory canal. See under Middle-Ear Inflammation, Acute and Chronic.
A boil may develop in the external auditory canal, and when this ruptures, pus may escape through the canal.
Purulent Discharge From the Eyes. The membrane covering the eyeball and lining the eyelids may become infected and produce pus, which escapes from between the lids. The common form of this disease is called acute conjunctivitis ("pink-eye"). A more serious condition is gonococcal conjunctivitis, caused by contamination with the gonorrhea germ, with a prolific discharge of yellow pus.
Purulent Discharge From the Lungs. Diseases of the lungs which may produce pus include tuberculosis, bronchiectasis, pneumonia (in the stage of resolution), pulmonary abscess, mycotic infections (as actinomycosis), and cancer. When the pus has easy access to the air passages, it is coughed up. In tuberculosis, this expectorated pus is laden with tuberculosis-producing germs. When pus within the lung cannot escape through the air passages, it accumulates to form an abscess. An abscess may break through, entering the space between the lung and the chest wall, producing empyema. The pus produced in fungous infections may even burrow through the chest wall, forming a fistula which discharges pus on the skin surface. A lung abscess may break into one of the bronchial tubes, in which case the patient may cough up large quantities of pus within a few hours.
Purulent Discharge From the Nose. A persistent purulent discharge from the nose is usually caused by sinusitis (an infection of the nasal sinuses). In early or acute sinusitis the discharge is watery and profuse, becoming more viscid and scanty as the condition becomes chronic.
Purulent Discharge From the Urethra. Urine is produced in the kidneys and then transferred through the ureters to the bladder, where it is stored until urination. On leaving the bladder, urine flows through the urethra to the outside. When pus is produced in the kidneys, ureters, or bladder, it mixes with urine and can be detected by the finding of pus cells on microscopic examination of the urine. Infections of the kidney and the bladder (cystitis) thus produce pus which mixes with the urine and is diluted by it. Cancer of the bladder, if infected, will do the same.
Pus originating from an infection within the urethra may appear at the external opening of the urethra as undiluted pus - not mixed with urine. Infection of the urethra is usually caused by a venereal disease - either gonorrheal or "nonspecific." Pus from a gonorrheal infection is highly contaminated by germs and can readily transmit the disease to another person or to some other part of the victim's body (as the eye) from contact by hands, clothing, or bath water.
Purulent Discharge From the Vagina. See also Leukorrhea. Mild degrees of vaginal discharge occur commonly. Unhealthy conditions of the vagina usually produce a more copious discharge, a condition called leukorrhea. A heavy vaginal discharge typically accompanies a gonorrheal infection. Pus may pass through the vagina after the rupture of an adjacent abscess in the vicinity of the rectum. In cancer of the uterus, pus (usually mixed with blood) is often discharged through the vagina.