Unilateral salpingo-oophorectomy is the surgical removal of a fallopian tube and an ovary. If both sets of fallopian tubes and ovaries are removed, the procedure is called a bilateral salpingo-oophorectomy.

This surgery is performed to treat ovarian or other gynecological cancers, or infections caused by pelvic inflammatory disease. Occasionally, removal of one or both ovaries may be done to treat endometriosis, a condition in which the lining of the uterus (the endometrium) grows outside of the uterus (usually on and around the pelvic organs). The procedure may also be performed if a woman has been diagnosed with an ectopic pregnancy in a fallopian tube and a salpingostomy (an incision into the fallopian tube to remove the pregnancy) cannot be done. If only one fallopian tube and ovary are removed, the woman may still be able to conceive and carry a pregnancy to term. If both are removed, however, the woman is rendered permanently infertile. This procedure is commonly combined with a hysterectomy (surgical removal of the uterus); the ovaries and fallopian tubes are removed in about one-third of hysterectomies.

From http://www.surgeryencyclopedia.com/Pa-St/Salpingo-Oophorectomy.html