The ABCs of Kidney Disease

Home | Contact | Search

A. Introduction

B. Normal Kidney Structure

C. Symptoms of Kidney Disease

D. Causes of Kidney Disease

E. Conclusions

A. INTRODUCTION

Kidney disease is a major health problem in this country.
More than 250,000 people are currently on dialysis (artificial kidney treatments) in the U.S.
More awareness of kidney disease by the public and professionals alike may ultimately reduce the incidence of this problem.
This discussion will give a brief overview of normal kidney structure and function as well as discuss the most common causes of kidney disease.

B. NORMAL KIDNEY STRUCTURE

I. Anatomy

Most individuals are born with two kidneys, although 1 in 1,000 people have only one.
The kidneys are ordinarily situated in the back of the abdomen near the lower ribs.
Blood flow to the kidneys comes from two renal arteries which arise from the aorta, the body's main artery.
This blood is then passed through millions of "filters" which leads to the production of urine.
Urine is then sequentially passed through ureters into the bladder and ultimately out of the body.
The newly cleansed blood returns to the circulation via the renal veins.

II. Microscopic Anatomy

Under the microscope the kidneys are comprised of many "filters" termed nephrons.
These nephrons are the functional units of the kidneys; they perform the majority of the kidney's necessary work.
Each kidney contains about 1 million nephrons.
Structurally, the nephrons are composed of blood vessels, glomeruli ("filtering units"), tubules ("conduits"), and supporting connective tissue.
Diseases may affect any of these structures potentially leading to kidney failure.

III. Kidney Function
The structural components of the kidneys perform a number of important functions which are critical to maintaining good health:

Remove a variety of waste products from the body by the production of urine.
Maintain fluid balance.
Regulate blood pressure.
Produce hormones.

Vitamin D - increases intestinal absorption of calcium and strengthens bones.
Erythropoietin (EPO) - regulates production of red blood cells.

C. Symptoms of Kidney Disease

Unfortunately, symptoms of kidney disease are generally subtle and often occur only late in the disease, making early detection difficult.

Some of the potential symptoms are listed below:

Swelling.
Blood in the urine.
High blood pressure.
Decreased urination.
Loss of energy.
Loss of appetite.
Nausea and vomiting.

D. Causes of Kidney Disease

Hundreds of different kidney diseases have been described, but recent reports suggest that a few diseases cause more than 85 percent of all kidney failure in the U.S.

I. Diabetes Mellitus

Causes 35 percent of end-stage renal disease (ESRD) in the U.S.
30-40 percent of people with insulin dependent diabetes mellitus (IDDM) may develop kidney disease.
Kidney disease is less frequent in people who have non-insulin dependent diabetes mellitus (NIDDM).
Diabetes damages the filtering units (glomeruli) within the kidneys, potentially causing kidney failure.
Slowly progressive (over 5-10 or more years) kidney failure is typical of people with diabetic kidney disease.
Treatment measures:
- Tight control of blood sugars, when done early, may prevent diabetic kidney disease. However, once advanced diabetic kidney disease is present, there is no good evidence that tight blood sugar control prevents worsening kidney function.
- Control of blood pressure represents the most important measure in slowing the progression of diabetic kidney disease.
- Use of specific blood pressure medications - recent evidence suggests that certain blood pressure medicines (i.e., Captopril and other ACE inibitors) may have special protective effects in people with diabetic kidney disease.
- Dietary protein restriction - some evidence suggests that low protein diets may slow disease progression. However, a recent, large, study demonstrated little, if any, benefit.
- Renal replacement therapy - necessary once very severe kidney disease develops. Options include hemodialysis, peritoneal dialysis, and kidney transplantation.

II. Hypertension (High Blood Pressure)

Hypertension is the second most common cause of ESRD in the U.S. currently accounting for about 30 percent.
Uncontrolled blood pressure leads to damage to the small blood vessels in the kidneys.
This damage leads to a lack of blood flow to the kidneys and often progressive kidney failure.
Prevention primarily involves good blood pressure control (i.e., < 140/90).
If severe kidney failure occurs, dialysis and transplantation are treatment options.

III. Glomerulonephritis

Refers to the many causes of damage to the glomeruli or "filtering units"; years ago, was known as Bright's disease.
Symptoms include swelling, blood/protein in the urine, flank pain, and high blood pressure.
At times the diagnosis can be made based upon blood test results. However, a kidney biopsy is often needed to make an exact diagnosis.
Treatment depends upon the specific cause of the glomerulonephritis.
Dialysis or transplantation is often available to those who develop severe kidney failure.

IV. Polycystic Kidney Disease

Polycystic kidney disease is a relatively common, inherited kidney problem.
Two main varieties exist:
- Autosomal recessive (infantile).
- Autosomal dominant (adult).
The adult type is more common, affecting every 1 in 600-1,000 people.
Approximately 5 percent of people on dialysis have polycystic kidney disease.
In these conditions, fluid filled sacs form within the kidneys.
These sacs may enlarge over time to cause kidney failure.
Symptoms of polycystic kidney disease:
- Flank pain.
- Kidney stones.
- Urinary tract infections.
- Blood in the urine.
- High blood pressure.
- Slowly (over many years) kidney failure may develop.
Treatment:
- Treat infections/stones as they arise.
- Control high blood pressure.
- Dialysis or transplantation.

E. Conclusions

The kidneys are the "master chemists" of the body.
Normally they are very efficient at maintaining body fluid composition and blood pressure.
However, a number of diseases can affect the kidneys, potentially leading to kidney failure.
Treatment depends upon the specific underlying cause, but control of high blood pressure is often one of the most important measures.
If end-stage renal disease develops, dialysis, or transplantation can maintain a good quality of life.