Kidney Disease:  When Those Fabulous Filters Are Foiled
by Ken Flieger 

        What is man . . . but a minutely set, ingenious machine for 
    turning, with infinite artfulness, the red wine of Shiraz into urine? 
                                Isak Dinesen
                             Seven Gothic Tales 

Most of us think of ourselves as more than just ingenious machines. But Isak
Dinesen was certainly right about the artfulness with which the human body, 
day in and day out, reduces everything eaten or drunk red wine or milk, a 
lamb chop or a bowl of rice into the nutrients that sustain life. Plus a
couple of quarts of urine.

Behind the lower ribs on either side of the spine are a pair of organs whose
major life-sustaining function is both mundane and elegant simple in
principle, yet so complex it has yet to be fully explained by science.
Through elaborate processes of extraction and reabsorption, these two 
fist-sized, bean-shaped organs the kidneys cleanse circulating impurities 
and excess fluid from the blood and change them into urine. 

If the kidneys falter or fail, we lose an internal pollution control system 
without which virtually every other bodily process becomes awash in 
potentially toxic wastes. And that's not all. Besides purifying blood, the
kidneys synthesize hormones and vitamins that control growth and help 
control blood pressure, regulate the production of red blood cells, and 
maintain the right balance of minerals and chemicals in the body. 

                         The Body's Master Chemists 

Every 24 hours kidneys process some 200 quarts of fluid brought to them by
the circulating blood. In a typical day, about 1 percent of that fluid two
quarts is excreted as urine. The other 198 quarts cleansed, restored to the 
proper acid-alkaline balance, and adjusted to contain the mix of minerals 
and chemicals the body needs to function normally are returned to the 
bloodstream.

The workers in this remarkable process are about 1 million nephrons (from 
the Greek for kidney). Each nephron consists of a filtering unit a
glomerulus attached to a tubule. Blood entering the glomerulus is filtered
to get rid of wastes produced by cellular activity in the body. The filtered
fluid travels along the tubule, where chemicals and water are either added
or removed depending on the body's current needs. Finally the excess fluid
and waste materials, in the form of urine, pass from the kidney and move
through tubes called ureters to the bladder. Urine is held there for one to 
eight hours and is then excreted. 

The urine of a normal healthy person is sterile; in an emergency it can 
safely be used to clean a wound. The color normally ranges from pale to dark
yellow depending on what and how much a person has had to eat and drink, the
amount of recent vigorous exercise, the use of medications, and other 
factors.

The odor of normal urine is faintly pungent, but again, diet and medicines
can change the odor without indicating that anything is wrong. (Detailed
discussions of how the kidneys work are found in The Kidneys: Complex 
Cleansing Units in the December 1981-January 1982 FDA Consumer and
Urinalysis: Looking into the Void in the October 1989 FDA Consumer.)

                            When Things Go Wrong

Diseases of the kidneys and urinary tract are among the most common major 
illnesses affecting Americans. The National Institute of Diabetes and 
Digestive and Kidney Diseases, one of the National Institutes of Health in
Bethesda, Md., estimates that between 20 million and 25 million Americans 
have kidney, urinary tract, or related diseases. Some 260,000 people die
each year from these illnesses. More than 140,000 Americans were being
treated in 1988 for kidney failure, or what is termed end-stage renal 
disease.  The number of such patients is rising at a rate of 10 percent 
annually. 

Although the exact cause of much kidney disease remains a mystery, it's 
clear that other conditions can increase the risk of kidney problems. For 
example, about 50 percent of people with Type 1 (juvenile onset) diabetes 
and 10 percent of those with Type 2 (adult onset) diabetes will develop 
kidney disease leading to permanent kidney failure. Because diabetes damages
small blood vessels throughout the body, vessels in the kidneys of a person 
with diabetes are less able to filter the blood. That leads to fluid
retention (edema) and the accumulation of toxic wastes, typical 
manifestations of advancing kidney disease. 

High blood pressure can be both a cause and a result of diseased kidneys. In
uncontrolled hypertension, blood vessels in the kidneys become thickened and
rigid, reducing the flow of blood and impairing filtering efficiency. A 
vicious circle is set in motion: The kidneys, damaged by high blood 
pressure, are less able to remove water and salt. Edema develops, putting an
added burden on the heart and causing a decline in blood flow. The result is
a further loss of kidney function and eventual kidney failure.

                              Types of Disease

Kidney diseases generally fall into one of three categories hereditary, 
congenital or acquired. Hereditary conditions usually produce symptoms from 
teenage years to adulthood. The most common is polycystic kidney disease
(PKD), in which, for reasons unknown, destructive cysts form in both kidneys
and sometimes in the liver, pancreas, colon, blood
vessels, and heart valves. Over a long period usually a number of years the 
growth of cysts impairs kidney function. Most people with PKD lead normal 
lives until they have lost 90 percent or more of kidney function, usually 
after age 40. Some PKD patients never experience renal failure or don't 
develop it until they are much older. 

Congenital kidney disease is present at birth and usually involves a
malformation of the genitourinary tract, typically an obstruction that makes
the patient susceptible to urinary infection and destruction of kidney
tissue. Eventually the destruction can progress to chronic kidney failure.

Acquired kidney diseases are numerous and are often lumped together under 
the generic term nephritis, meaning inflammation of the kidney. The most
common form of acquired kidney disease is glomerulonephritis, in which the
glomerulus is the chief site of injury. 

Glomerulonephritis can be either acute or chronic. The acute form develops a
couple of weeks after a streptococcal infection, usually a sore throat or 
skin infection, and is most often seen in children and young adults. The
symptoms loss of energy, pallor, puffiness around eyes and ankles, and
ultimately blood in the urine persist for several weeks. Most people with 
acute glomerulonephritis recover fully, though complete recovery may take a 
year. In 2 to 3 percent of cases, however, complications including heart or 
kidney failure, high blood pressure, and convulsions?are fatal. 

Unlike the acute form, chronic glomerulonephritis involves progressive
kidney failure and is the most frequent cause of end-stage renal disease. In
the early stages, the only sign that the patient is ill may be abnormal 
findings in a urinalysis typically red and white blood cells and protein in 
the urine. If the kidneys are beginning to lose function, the patient may 
have high blood pressure. 

As the disease progresses, hypertension becomes persistent and difficult to 
treat. With severe loss of kidney function, patients experience diminished
appetite, nausea and vomiting, extreme fatigue, difficulty sleeping, itching
and dry skin, and muscle cramps.

Yet another kind of glomerulonephritis, rapidly progressive 
glomerulonephritis, is marked by accelerated kidney failure. It appears 
suddenly, is characterized by a decrease in urine output, and is
irreversible. 

                               Disease Product

Strictly speaking, kidney stones are not a disease but the product of a 
disease. Nevertheless, the more than 800,000 Americans treated for this 
ailment each year know that kidney stones can cause excruciating pain before
they pass out of the body by themselves or are cut out on the operating 
table. Stones can be caused by hereditary factors, diet, occupation,
metabolic disturbances, the amount of water a person consumes, and even 
climate. The fact is, scientists are not entirely sure why some people
develop kidney stones while mercifully most don't. Nor do they understand 
why black people have far fewer stones than do whites or why three males are
affected for every female.

Most kidney stones are hard masses of salt and mineral crystals deposited on
the inner surface of the kidney. (Similar stones that form in the bladder or
pass from the kidney to the bladder via the ureter are properly called
bladder stones.) A stone that breaks loose from the kidney and passes 
through the ureter to the bladder and then through the urethra outside the
body may go entirely unnoticed. About 90 percent of stones do that. But 
sometimes they lodge somewhere en route through the urinary tract and 
continue to grow. This leads to tissue damage, internal bleeding, and the 
exquisite pain that is the hallmark of a stuck stone. 

                          Prevention and Treatment

Since many forms and individual cases of kidney disease are of unknown
cause, it's hard to identify preventive measures. On the basis of 
experience, though, scientists think that increasing urine output by
drinking fairly large amounts of liquids each day can lessen the risk of
kidney stones. A better understanding of metabolic factors that seem to be
involved in stone formation together with careful use of drugs to regulate
body chemistry may soon  make recurrent kidney stones a preventable 
condition.

The prospects for preventing the various forms of nephritis, whose causes 
are even less well understood, are not as bright. Keeping hypertension under
control, however, can have a bearing on the risk of developing nephritis. 
Moreover, adequate control of blood pressure is crucial in the care of
patients with kidney disease at every stage of their illness. 

People with diminished kidney function benefit from avoiding a diet high in 
sodium and protein as well as careful control of minerals such as potassium,
calcium and phosphorus. However, the value of diet in preventing kidney 
disease is uncertain. Diet isn't likely to lower the risk of developing 
inherited kidney disease, and it can?t help a baby born with a congenital 
malformation that will lead to kidney problems. 

Treatment of kidney disease depends on several factors, among them the exact
diagnosis, the stage of the disease, other illnesses that may be present, 
and the age and general condition of the patient. In some cases treatment 
may consist of little more than rest and dietary restrictions. In others, 
notably end-stage renal disease, the patient may benefit from such medical
marvels as an artificial kidney (dialysis) or a kidney transplant,
techniques that improve the quality of, and prolong, life for many thousands
of kidney disease patients. 

Kidney Stones. Stones that aren't causing any trouble, so-called silent 
stones, usually don't require treatment. Acute attacks, however, may demand 
hospitalization because the pain is so severe. In most cases, the stone is
small, and the patient needs medication to control pain and instruction on
how to recover the stone for examination when it passes.

If a stone gets lodged in the ureter, physicians may try to remove it in a
basket-like device passed into the ureter through a cystoscope, a hollow
tubular instrument that can be passed through the urethra to allow
visualization of the bladder. 

If a stone gets stuck in the bladder itself, it can be crushed by a tiny
instrument inserted via the cystoscope. The fragments are either washed out 
or allowed to pass in the urine. For stones lodged inside the kidney, 
physicians can insert a needle through the skin of a patient under local
anesthesia to create a passage directly to the stone. Instruments are then
passed through this passage either to remove or break up the stone. Stones
that are formed primarily of uric acid can sometimes be dissolved by the use
of drugs. But if neither medicines nor specialized instruments can be 
counted on to work, surgery may be the only option. 

Several years ago, FDA approved a device that uses high-intensity pressure
waves traveling through water to disintegrate some kinds of kidney stones 
and enable them to pass out of the body on their own. Known as
extracorporeal shock wave lithotripsy, the procedure may involve lowering a 
patient under local or general anesthesia into a tank of water in which a 
powerful electric or other source generates a shock wave that, with the aid 
of x-ray or sonographic imaging, is directed precisely at the stone to be 
shattered. Multiple shock bursts are fired at the stone, reducing it to 
fragments. Lithotripsy takes about an hour, and the patient is usually out
of the hospital in two days some are treated as outpatients and can resume
normal activities. (Patients who have surgery for kidney stones are 
generally hospitalized for several days and need up to five weeks to
recuperate.)

Another lithotripsy technique that uses a laser instead of shock waves was
approved by FDA in 1986. The laser, passed through a tube to the location of
the stone, reduces the stone to particles the size of grains of sand that 
are then excreted. Laser lithotripsy is especially useful in treating stones
in the lower ureter.

Nephritis. Treatment for the various kinds of nephritis aims chiefly at 
controlling kidney damage and dealing with the consequences of progressive
kidney failure. It can and often does involve a combination of dietary
restrictions, drugs, and, when the patient develops end-stage renal disease,
dialysis and transplantation of a donor kidney. 

The kind and degree of dietary restriction depends on the stage of a
patient's disease. In general, patients are advised to limit protein intake 
and be sure that a certain portion of it is high quality protein found in 
foods such as eggs, meat, fish, poultry, milk, and cheese. Because of its 
role in high blood pressure, sodium is sharply limited in the diets of most 
kidney disease patients. Calcium intake is also limited, requiring the
patient to limit consumption of milk and milk products. Patients on dialysis
may have to restrict potassium and water, but that?s not usually necessary
in the early stages of kidney disease.

Several kinds of medication can help manage the symptoms of kidney disease, 
though no specific drug is known to be effective against the fundamental
cause of nephritis. Steroidal anti-inflammatory agents, diuretics, and
antihypertensive drugs are useful in retarding kidney damage and lowering 
blood pressure. 

But eventually the disease will progress to a point at which the kidneys can
no longer cleanse the blood adequately. At that stage, life-saving measures 
are needed. 

                              Role of Dialysis

Dialysis is a procedure that artificially replaces some of the kidney's 
normal function, enough at least to allow most patients whose kidneys have
failed to live relatively normal lives. There are two types hemodialysis and
peritoneal dialysis. In hemodialysis, the patient's bloodstream is diverted 
to an external machine that continuously filters the blood, corrects its
chemistry, and returns it to the body.

Usually, hemodialysis patients are treated about three times a week. The
procedure can be carried out in a hospital, a dialysis center, or at home.
Home dialysis can be more convenient for the patient, but it requires that
the patient or care-giver be thoroughly familiar with the dialysis procedure
and equipment and the critical importance of measures to prevent
contamination of the blood supply. At home or in a health-care facility,
each dialysis treatment lasts about five hours. 

In continuous ambulatory peritoneal dialysis the patient's blood is not 
shunted outside the body. Instead, a catheter placed in the patient's 
abdomen allows the abdominal space to be slowly filled with a solution the
dialysate used to clean and re-balance the chemistry of blood flowing 
through vessels in the abdomen. After about four or five hours, the 
dialysate is allowed to drain through the catheter and a fresh supply is
introduced. The procedure is repeated several times a day while the patient 
goes about normal activities. 

Cycling peritoneal dialysis is basically identical. It, however, requires an
external machine and is usually done for about an hour and a half at night
while the patient sleeps. Intermittent peritoneal dialysis is a hospital
procedure that takes 10 to 12 hours. The oldest form of dialysis, it is 
often used in emergencies or as the first dialysis procedure following total
kidney failure. 

                    Help for Patients with Failed Kidneys 

Patients suffering from chronic kidney failure frequently have severe anemia
because the kidneys cannot produce enough erythropoietin, a hormone that
stimulates red blood cell production. As a result, they need frequent 
transfusions, which raises the risk of infection from contaminated blood and
eventually causes a dangerous build-up of iron. In June 1988, FDA approved
Epogen, genetically engineered erythropoietin that can be administered to 
patients to boost their red cell production, thereby sharply lowering the 
need for transfusion. 

With present incomplete knowledge of the cause and cure of kidney disease,
transplantation offers an alternative to repeated dialysis for patients who 
have end-stage kidney failure. Some 7,000 Americans a year receive a kidney 
transplant, but about 60 percent of them need long-term treatment to prevent
their own immune systems from attempting to reject the transplanted kidney. 
The anti-rejection drug Sandimmune (cyclosporine) is widely used in these 
cases, as are steroids such as prednisone. In June 1988, FDA approved a new 
agent to reverse acute kidney transplant rejection, Orthoclone OKT3 
(muromonab-CD3). The drug blocks the action of T-cells, the white blood 
cells that are responsible for the body's rejection of foreign tissue.

The treatment of kidney failure is one of the most successful and beneficial
applications of modern medical science. Although there is still a long road 
ahead to effective prevention or cure, current medical developments give
those with a diagnosis of kidney disease strong reasons to be optimistic
about treatment.

Ken Flieger is a free-lance writer in Washington, D.C.