Nephrology is the branch of internal medicine that focuses on care of the kidneys, and diagnosis and treatment of kidney disease and disorders. Many kidney problems are systemic, and require medical evaluation and intervention not only by nephrologists, but by specialists in other fields, such as immunology or rheumatology.
The human body has two kidneys, which are located at the back of the abdomen; each is approximately the size of the human fist. The kidneys act as filters by removing waste from the blood, and producing urine, a fluid that contains the waste. As urine is collected, it passes into the bladder through tubes called "ureters." When the bladder is full, urine passes through the urethra, and out of the body.
Function of the Kidney
Several times each day, all of the blood in the body passes through the kidneys to be cleared of waste. Kidneys perform the following functions:
- Remove waste products from the blood
- Regulate the balance of fluids in the body
- Regulate the body's electrolyte balance
Each kidney contains approximately one million microscopic units called "nephrons." Each nephron functions as a tiny filter, assisting in the removal of waste from the blood. Because of the huge number of nephrons, it is possible for a person to lose as much as 90 percent of kidney function yet remain asymptomatic.
Disorders of the Kidney
There are many disorders, including the following, that affect the kidneys:
- Congenital disorders (such as polycystic kidney disease)
- Infectious diseases (such as pyelonephritis)
- Inflammatory disorders (such as glomerulonephritis, interstitial nephritis)
- Abnormalities (such as kidney stones, renal cysts, nephrogenic diabetes insipidus)
- Kidney cancer
- Diabetic or hypertensive nephropathy
- Imbalance of electrolytes, or acids and bases
- Acute or chronic kidney failure
The most common type of kidney cancer in adults is renal-cell carcinoma; it usually affects men between 50 and 70 years old.
Diagnosis of Kidney Problems
Nephrologists employ many tests in diagnosing kidney disease and dysfunction. After a patient is given a thorough physical examination and provides a detailed medical history, the following tests may be performed: urinalysis, which checks urine for the presence of blood, protein, pus, and cancer cells; 24-hour urine collection, which measures urine output, daily loss of protein and creatinine clearance; blood tests, which establish the concentration of hemoglobin, platelets, and various minerals and secretions in the blood; specialized tests, which check for the presence of infections and autoimmune problems; diagnostic imaging tests, which check for structural abnormalities of the kidneys; and renal biopsies, which detect cancer and other types of disease.
Treatment of Kidney Disorders
Nephrologists treat kidney disorders, depending on their type and severity, in a variety of ways. Treatments for kidney disease include the following:
- Nephrostomy (catheter inserted directly into kidney to drain urine)
- Lithotripsy (shock waves used to shatter kidney stones)
- Nephrectomy (cancerous/severely damaged kidney is surgically removed)
- Hemodialysis (dialysis machine filters blood when kidneys fail)
- Peritoneal dialysis (fluid is siphoned into abdomen, and then drained, to filter blood)
A kidney transplant is necessary when kidneys are unable to function. Kidney-transplant donors may or may not be related to the transplant recipient.