At this time no vaccine is available to prevent people from becoming infected with HIV and studies of various vaccines have been disappointing. The virus mutates (that is, its surface proteins change) quickly. Because vaccines are usually directed against surface proteins in an effort to kill the virus, such subtle but important changes in the virus over time mean that a vaccine that may be effective at one time may not be effective a short while later. With the rapid spread of HIV throughout the world—especially in areas where people are not able to afford expensive treatments once they become infected—the development of an effective vaccine is imperative.

Infection takes place in three ways—sexual transmission, exchange of blood or other body fluid, and exchange of fluids from mother to child—and these are now discussed in detail.

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incidence: common

cause: bacterium (Neisseria gonorrhoeae)

symptoms: burning with urination, discharge, pelvic pain, spotting

between periods

treatment: antibiotics

WHAT IS IT?

Gonorrhea is a sexually transmitted infection caused by the bacterium Neisseria gonorrhoeae. This bacterium can cause a number of genital infections, including urethritis, epididymitis, and prostatitis in men and urethritis, cervicitis, and pelvic inflammatory disease (PID) in women. Women who have had hysterectomies can contract a gonorrheal infection in the urethra and genital glands. The bacterium can also cause infection of the throat, conjunctiva, and rectum, joint infection; and meningitis. Recently it has been found that people who become infected with gonorrhea may be at increased risk of acquiring and transmitting other sexually transmitted diseases, including human immunodeficiency virus (HIV) infection.

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Studies indicate that about 4 percent of women in the United States label themselves as being lesbian. This statistic probably significantly underestimates the number of women who have sex with other women; one study showed that up to 18 percent of women experienced attraction to other women or were in sexual relationships with other women. When labels are assigned to a minority group, and especially when those labels have certain negative connotations, people may be hesitant to claim membership in that group.

Many women who have sex with female partners do not believe that they are at risk for sexually transmitted infections, and health care providers may also believe that these women are not at risk. This is partly because there have not been many studies of the rates of STDs among lesbians, but it may also be because of bias against those in same-sex relationships. Even if lesbian women do turn to traditional health care providers for care, they may experience the homophobia of a health care provider or receive incorrect advice, such as "gay women don't need Pap smears." Many lesbian women find a more open approach at clinics that specialize in the health care of women.

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Like the PLCO study, the PIVOT study is long; it has a three-year enrollment period, and a twelve-year follow-up; 2,000 men will be able to participate. Men up to age 75 are eligible—but these older men, like the rest of the men in the study, must be healthy enough to be considered fit for surgery. Only men with prostate cancer who are considered candidates for surgery may take part in the study; they will be assigned to one of two groups—either they'll undergo a radical prostatectomy, or they will be followed closely with watchful waiting and treated as needed for specific symptoms or metastases. Many cancer centers and Veterans Administration hospitals throughout the country are participating in this study.

What's the measure of success here? It's what you might call the ultimate endpoint—death or survival. "Really, that's what the patient cares about," says the internist. "Will my disease be cured? Is my life better without the surgery? We don't know the answer to either of those questions. Those in favor of radical prostatectomy say, 'How can doctors dare not treat? They're killing people with watchful waiting!' And the watchful waiting people say that surgery doesn't prolong survival. These are two groups of intelligent, caring people, and there is information to support either of these two views."

Men in the study will be examined at least every three months the first year and every six months afterward, and periodically they will answer questionnaires about their quality of life. Their doctors will check for any evidence that prostate cancer has progressed, and they will document any changes in the patients' condition. If the patient dies, for any reason, all of this information will go to an independent review committee, which will study all the accumulated data and determine whether the man's death was definitely, probably, possibly, or definitely not due to prostate cancer.

The PIVOT study is interesting for several reasons; despite the age limit of its patients—it's hard to know how many 75-year-old men will be around for the study's conclusion—the selection criteria seem fairly strict. Men who obviously are not good candidates for surgery, the study's directors say, will not be included. Also, because of its size, the study promises highly specific results.

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We begin with the kidneys, which lie like bean-shaped bookends, embedded fat and fibrous connective tissue, on either side of the spine at the base of th ribs. They're located behind the pancreas and beneath the peritoneum, the large sheet of tissue lining the abdomen that encloses and protects the liver, stomach, and bowel.

The kidneys are reddish-brown, and they're not mirror images. The left kidney tends to be slightly longer, narrower, and situated a little higher than the right, which occupies somewhat cramped quarters just below the liver. The kidneys, on average, are about five inches long, three inches wide, and an inch thick. They are highly vascular: Pound for pound, the kidney handles three to five times more blood than the heart, liver and brain. An amazing 25 percent of the blood from each heartbeat flows through them, and the kidneys cleanse the blood of toxic wastes, excess water and salts. They play a pivotal role in maintaining the body's balance of fluids and electrolytes (minerals such as sodium, potassium and chloride), as well as the acid-base (pH) ratio in the body. They help metabolize vitamin D, which strengthens bones. They also manufacture renin, which helps regulate blood pressure; and erythropoietin, which regulates the body's red blood cell count.

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