▸ Kidney Damage Many diseases, injuries, and exposure to hazardous substances can lead to impaired kidney function. But most cases of kidney damage in the United States are related to high blood pressure and diabetes. Excessive blood pressure damages the delicate filtering mechanism, and high blood sugar levels cause the kidneys to filter more blood than normal. Over time, the tubules weaken, and the kidneys may fail to keep up with the demands placed upon them.

▸ Kidney Failure When kidneys can no longer cleanse the blood and maintain a state of homeostasis in the body, a person is said to be in kidney failure. A patient with kidney failure must receive dialysis or undergo a kidney transplant as shown in Figure 30–20.

During dialysis, a machine performs the role of the kidneys. The patient's blood is pumped through the machine, cleansed, and pumped back into the body. Although the procedure is painless, it is very time-consuming. Most patients receive dialysis treatments three times a week for about four hours each time. To prevent the buildup of fluid and harmful materials between treatments, patients must restrict their fluid intake and eat foods low in potassium, phosphorus, and salt.

In transplantation, a patient receives a kidney and ureter from a compatible donor. Fortunately for the donor, a person can survive with just one healthy kidney.

FIGURE 30–20 Kidney Transplantation Unless the patient's diseased kidneys are causing infection or high blood pressure, they are left in place when a healthy kidney and ureter are transplanted from a donor.

d

30.4 Assessment

Review Key Concepts

1. 1. Review List the organs that are involved in excretion.

   2. Classify Why is excretion important for homeostasis?

2. 1. Review What substances do the kidneys remove from blood?

   2. Sequence Explain what happens during filtration, reabsorption, and urine excretion.

3. 1. Review Describe how the kidneys help maintain water balance.

   2. Apply Concepts Why do you think protein and glucose in the urine are signs of kidney damage?

BUILD VOCABULARY

4. Two words that are often used interchangeably are excretion and secretion. They have two distinct meanings, however. An excretion is usually a waste product of metabolism that is expelled from an organism. A secretion is a useful substance that is released inside or outside an organism. Name one example each of an excretion and a secretion from this lesson.

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