HUMAN BIOLOGY

234 Chapter 12

As this chapter’s introduction noted, urinalysis

provides a chemical snapshot of many physiological

processes in the body. It also can be quite helpful

in diagnosing illness. For example, glucose in urine

may be a sign of diabetes, and white blood cells

(pus) frequently indicate a urinary tract infection.

Research this topic to find out some other common

medical uses of urinalysis.

THiNK OuTSiDe THe BOOK

Cancer, infections, and Drugs in the urinary system

around the capillaries that service the glomerulus, hamper-

ing or preventing the flow of blood. Then blood filtering

becomes difficult or impossible.

In both sexes, urinary tract infections sometimes result

from sexually transmitted microbes, including the micro-

organisms that cause chlamydia. Chapter 16 gives more

information on this topic.

painkillers and other drugs may harm

the kidneys

Over-the-counter painkillers such as aspirin, acetamino-

phen, and NSAIDs (nonsteroidal anti-inflammatory drugs

such as ibuprofen) come with consumer warnings about

possible kidney damage. These drugs usually are safe

when used according to directions. According to the

National Kidney Foundation, however, millions of Ameri-

cans have unwittingly destroyed their kidneys by excessive

use of these substances. Experts recommend that people

who must take large amounts of such painkillers drink six

to eight glasses of water a day to help flush harmful resi-

dues from the kidneys.

Heavy alcohol use also is hard on the kidneys, and some

illegal street drugs—including amphetamines, cocaine,

and heroin—can cause major kidney damage.

urinary system cancer is on the rise

Carcinomas of the bladder and kidney (Figure 12.13)

account for about 100,000 new cancer cases each year, a

number that is increasing. The incidence is higher in males,

and smoking and exposure to certain industrial chemicals

are major risk factors. Kidney cancer easily metastasizes

via the bloodstream to the lungs, bone, and liver. An inher-

ited type, called Wilms tumor, is one of the most common

of all childhood cancers.

urinary tract infections are common

Urinary tract infections plague millions of people. Women

especially are susceptible to bladder infections because of

their urinary anatomy: The female urethra is short, just a

little over 1 inch long. (An adult male’s urethra is about

9 inches long.) The outer opening of a female’s urethra also

is close to the anus, so it is fairly easy for bacteria from out-

side the body to make their way to a female’s bladder and

trigger an inflammation called cystitis—or even all the

way to the kidneys to cause pyelonephritis.

Nephritis is an inflammation of the kidneys. It can be

caused by various factors, including bacterial infections.

As you may remember from Chapter 9, inflamed tissue

tends to swell as fluid accumulates in it. However, because

a kidney is “trapped” inside the tough renal capsule, it

can’t increase in size. As a result, pressure builds up in or

© Cengage Learning/Gary Head

Figure 12.13 More than 50,000 cases of kidney cancer are

diagnosed each year in the United States. This photograph

shows a tumor in a kidney, which has been cut open to reveal

the cancer’s location (the circular area on the bottom).

Dr. E. Walker/Science Source

kidney

ureter

cancer

tumor

12.7

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