Definition:  Pelvic Inflammatory Disease (PID) is a general term that refers to infection of the uterus, fallopian tubes, and other reproductive organs in women.

PID is a common and serious complication of some sexually transmitted infections, especially Chlaymdia and Gonorrhea, when left untreated.  PID is a cause of infertility and ectopic pregnancy (pregnancy growing outside the uterus).
Symptoms of PID vary from none to severe. When PID is caused by Chlamydial infection, a woman may experience mild symptoms or no symptoms at all, while serious damage is being done to her reproductive organs. Because of vague symptoms, PID goes unrecognized by women and their health care providers about two thirds of the time. Women who have symptoms of PID most commonly have the following symptoms:

Symptoms of PID 

• Lower abdominal pain
• Fever
• Unusual vaginal discharge that may have a foul odor
• Painful intercourse
• Painful urination
• Irregular menstrual bleeding
• Pain in the right upper abdomen, though rare

Information on this page provided by the US Centers For Disease Control and Prevention,  http://www.cdc.gov/std/Gonorrhea/STDFact-gonorrhea.htm and
http://www.cdc.gov/std/PID/STDFact-PID.htm