The kidneys play a critical role in the body: Acting as the
body's filtering system, they help control water levels and
eliminate wastes through urine. They also help regulate blood
pressure, red blood cell production, and the levels of calcium and
minerals.
But sometimes the kidneys don't develop properly and, as a
result, don't function the way that they should. Often these
problems are genetic and not due to anything a parent did or didn't
do.
Many of these problems can be diagnosed before a baby is born
through routine prenatal testing and treated with medication or
surgery while the child is still young. Other problems may emerge
later, such as symptoms of urinary infections, growth retardation,
high blood pressure, etc. In some cases, the problems are more
severe and require more extensive surgical treatment.
How the Kidneys Work
The kidneys are like the body's garbage collection and disposal
system. Through microscopic units called
nephrons
, the kidneys remove waste products and extra water from the food a
person eats, returning chemicals the body needs (such as sodium,
phosphorus, and potassium) back into the bloodstream. The extra
water combines with other waste to become urine, which flows
through thin tubes called
ureters
to the bladder, where it stays until it exits through the
urethra
(the tube that carries urine out of the body from the bladder) when
someone goes to the bathroom.
The kidneys also produce three important hormones:
erythropoietin
, which stimulates the bone marrow to make red blood cells;
renin
, which helps regulate blood pressure; and the
active form of vitamin D
, which helps control the calcium balance in the body and maintain
healthy bones.
Kidney failure
, which is also called
renal failure
, is when the kidneys slow down or stop properly filtering wastes
from the body, which can cause build-ups of waste products and
toxic substances in the blood. Kidney failure can be
acute
(which means sudden) or
chronic
(occurring over time and usually long lasting or permanent).
- Acute kidney failure may be due to bacterial infection,
injury, shock, heart failure, poisoning, or drug overdose.
Treatment includes correcting the problem that led to the
failure, and in rare cases requires dialysis.<
- Chronic kidney failure involves a deterioration of kidney
function over time. In kids and teens, it can result from acute
kidney failure that fails to improve, birth defects, chronic
kidney diseases, or chronic severe high blood pressure. If
diagnosed early, chronic kidney failure can be treated. The goal
of treatment usually is to slow the decline of kidney function
with medication, blood pressure control, and diet. At some point,
a kidney transplant may be required.
Childhood Kidney Diseases
The most common kidney diseases in children are present at
birth. They include:
Posterior urethral valve obstruction:
This narrowing or obstruction of the urethra affects only boys. It
can be diagnosed before the baby is born or just afterwards and
treated with surgery.
Fetal hydronephrosis:
This enlargement of one or both of the kidneys is caused by either
an obstruction in the developing urinary tract or a condition
called
vesicoureteral reflux
(VUR) in which urine abnormally flows backward (or refluxes) from
the bladder into the ureters. Fetal hydronephrosis is usually
diagnosed before the child is born and treatment varies widely. In
some cases the condition only requires ongoing monitoring; in
others, surgery must be done to clear the obstruction from the
urinary tract.
Polycystic kidney disease (PKD):
This is a condition in which many fluid-filled cysts develop in
both kidneys. The cysts can multiply so much and grow so large that
they lead to kidney failure. Most forms of PKD are inherited.
Doctors can diagnose the condition before or after the child is
born. In some cases, there are no symptoms; in others, PKD can lead
to urinary tract infections, kidney stones, and high blood
pressure. Treatment for PKD also varies widely. In some cases, PKD
can be managed with dietary changes; in others, it requires a
kidney transplant or dialysis, which is a medical treatment that
helps the body filter waste when the kidneys can't do the job.
Multicystic kidney disease:
This is when large cysts develop in a kidney that hasn't developed
properly, eventually causing it to stop functioning. (While PKD
always affects both kidneys, multicystic kidney disease usually
affects only one kidney.) Usually diagnosed before a baby is
born, this condition can lead to kidney failure. Currently, there
is no cure, but doctors can manage it by preventing and treating
infections, maintaining blood pressure, and addressing any issues
that arise with surgery.
Renal tubular acidosis:
This is a condition in which the kidneys do not properly regulate
the amount of acid in the body. It can cause kidney stones and
affect a child's growth, but usually can be treated with
medications.
Wilms tumor:
This is a type of
childhood cancer
that involves the kidney. It is typically diagnosed within the
first 2 years of life and can be treated with surgery and
chemotherapy.
Glomerulonephritis:
This is an inflammation or infection of the glomeruli, which are
parts of the nephrons that contain tiny blood vessels. It can
affect the kidney's ability to properly filter out waste and can
lead to swelling, blood in the urine, and a reduced amount of urine
production. Some cases can be treated with medication, while others
require dialysis or a kidney transplant.
Nephrotic syndrome:
This occurs when the body loses large amounts of protein through
the urine, typically because of some sort of change in the
nephrons. It is usually diagnosed after the child is 1 year old.
Swelling of the face, abdomen, and extremities are among the main
symptoms, and are often relieved with medication.
Congenital problems with the urinary tract:
As a child develops in the womb, a part of the urinary tract can
grow to an abnormal size or in an abnormal shape or position. These
problems include:
-
duplication of the ureters
, in which a kidney has two ureters instead of one. This can lead
to urinary tract infections over time and can be treated with
medication or occasionally with surgery.
-
horseshoe kidney
, where the two kidneys are fused (connected) into one arched
kidney that usually functions normally, but is more prone to
develop problems later in life. An uncomplicated horseshoe kidney
does not need medical or surgical treatment, but it does need to
be checked regularly by doctors.
Other Problems With the Kidneys
Sometimes a child can have other health problems that affect how
well the kidneys function. These can include:
High blood pressure or hypertension.
The kidneys control blood pressure by regulating the amount of salt
in the body and by making the enzyme
renin
that, along with other substances, controls the constriction of
blood vessels. The many causes of high blood pressure include any
of the kidney diseases mentioned above; genetic factors such as the
so-called "essential hypertension," which is the most common form
of high blood pressure in adults; and obesity, which has become a
major factor.
Kidney stones.
The result of the build-up of crystallized salts and minerals such
as calcium in the urinary tract, kidney stones (also called
calculi) also can form after an infection. If kidney stones are
large enough to block the kidney or ureter, they can cause severe
abdominal pain. But the stones usually pass through the urinary
tract on their own. In some cases, they need to be removed
surgically, or treated with medication or modifications to the
diet. Sometimes the first symptoms are pain and blood in the urine.
Kidney stones are more common in adults than they are in kids.
Nephritis.
This is any inflammation of the kidney. It can be caused by
infection, an autoimmune disease (such as lupus), or an unknown
reason. The first symptoms of nephritis usually are high levels of
protein and blood in the urine.
Urinary tract infections (UTI).
UTIs are typically caused by bacteria, such as
E. coli
. Most UTIs occur in the lower urinary tract, in the bladder and
urethra, and they can cause pain during urination and a fever.
Treatment with antibiotics should be started as soon as possible so
the infection doesn't spread to the kidneys, where it can cause
irreversible damage. In babies, UTIs tend to be more common in boys
than girls, perhaps because boys are more affected by congenital
kidney problems that predispose them to infection. Later in life,
girls are more likely to get UTIs because of their shorter
urethras. Bad habits can contribute to UTIs - kids holding it when
they need to go to the bathroom, or wiping themselves in the wrong
direction after using the toilet (they should wipe from front to
back so bacteria from the stool do not get into the urethra). Among
teens, girls are more likely to develop UTIs than boys, mostly due
to the shorter urethra or sexual activity with a full bladder.
Symptoms of Kidney Problems
The signs and symptoms of urinary tract or kidney problems are
diverse and include:
- fever
- swelling around the eyes, face, feet, and ankles (also known
as edema)
- burning or pain during urination
- significant increase in the frequency of urination
- difficulty in controlling urination in children who are
mature enough to use the toilet
- recurrence of nighttime bedwetting (in children who have been
dry for several months)
- blood in the urine
- high blood pressure
Diagnosis of Kidney Diseases
If your child's doctor suspects a kidney disease in your child,
he or she will likely take a medical history, do a physical exam,
and order urine tests, blood tests, imaging studies, or a biopsy to
help make a diagnosis. These studies are usually suggested by a
nephrologist
, a doctor who specializes in the diagnosis and treatment of kidney
diseases.
With urinalysis (a type of urine test), your child's doctor can
quickly detect abnormalities (such as too many red blood cells)
that may signal inflammation or irritation in the urinary tract.
Urinalysis can also detect an of excess white blood cells, which is
most commonly associated with bladder and kidney infections.
Certain blood tests tell doctors how well the kidneys are
filtering waste products and balancing the bloodstream's chemical
makeup.
Two other important diagnostic tools a doctor may use are blood
pressure and growth measurements. Along with the heart, the kidneys
are crucial to determining blood pressure. High blood pressure in a
child is an important sign that the kidneys need to be evaluated.
Accurate growth measurements can provide a clue to diagnosing some
kidney diseases because children with chronic kidney disease often
grow poorly.
Your child's doctor may use a kidney biopsy to evaluate your
child's kidney function. A biopsy is a procedure in which a small
piece of the kidney tissue is removed with a needle. Performed
while a child is under anesthesia, it's a simple procedure that can
help make an accurate diagnosis of the kidney problem in about nine
out of 10 cases. It's especially helpful in the diagnosis of
nephritis and nephrosis.
The doctor also will take a medical history by asking you about
any concerns and symptoms, your child's past health, your family's
health, past medications, any allergies, and other issues.
In addition to standard X-rays, other imaging studies a doctor
may use to help diagnose kidney diseases include:
Ultrasound
The most commonly used imaging study, an ultrasound is painless
and requires no X-ray exposure or special preparation. A renal
ultrasound shows details of the anatomy of the kidneys and bladder.
It can rule out or diagnose obstructions, developmental
abnormalities, tumors, and stones in the kidneys and urinary
tract.
Computerized tomography (CT)
A CT scan is often helpful in revealing the anatomy of the
kidneys or bladder and, in some cases, is better than ultrasound
for finding kidney stones. It can show if the kidneys have
developed properly or if the flow of urine is blocked by a stone or
a developmental abnormality.
Renal nuclear scan
A renal nuclear scan involves having special radioactive
material injected into a vein. The radiation dose is less than that
of a simple X-ray. The scan shows how the kidneys compare to each
other in size, shape, and function. It also can detect scarring or
other evidence of recurrent or chronic kidney infection.
Voiding cystourethrogram (VCUG)
VCUG is commonly used to evaluate the bladder and the ureters.
This procedure involves putting a dye into the bladder to see
whether there's an obstruction or VUR when the child urinates.
Reviewed by:
Laszlo Hopp, MD
Date reviewed: February 2006
Note: All information is for educational purposes only. For specific medical advice,
diagnoses, and treatment, consult your doctor.
© 1995-2009 The Nemours Foundation/KidsHealth. All rights reserved.