Each time our internal organs do something, such as digesting food or healing damaged
tissue, chemical reactions take place in the body's cells. These reactions cause acid
to go into the bloodstream.
Normally, the kidneys
remove excess acid from blood, but certain diseases, genetic defects, or drugs can
damage a kidney's ability to do this important job. This can allow too much acid to
build up in the blood and cause problems. When this happens, it's called renal
tubular acidosis (RTA).
Without treatment, RTA can affect a child's growth and cause kidney
stones, fatigue, muscle weakness, and other symptoms. Over time, untreated acidosis
can lead to long-term problems like bone disease, kidney
disease, and kidney failure.
Fortunately, such complications are rare, since most cases of RTA can be effectively
treated with medicines or by treating the condition that's causing the acid to build
How the Kidneys Work
The kidneys are a pair of bean-shaped organs located toward the back of the
abdominal cavity, just above the waist. 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 (pee).
The main functional units of the kidneys, where the blood filtering happens, are
tiny structures called nephrons. Each kidney has about a million
nephrons, and each nephron has a renal tubule, a tube where the acid
and waste products filtered from the blood are secreted into urine.
Having a disease or defect can interfere with how the renal tubules function, which
can lead to RTA.
There are a few different kinds of RTA. The first two types are named for the part
of the renal tubule in which the damage or defect is found.
Type 1 RTA, or distal renal tubular acidosis,
is the most common kind of RTA. Distal means that the defect is relatively far from
the beginning of the tubule. Distal RTA can be inherited or caused by high blood calcium,
sickle cell disease,
autoimmune disorders like lupus
and Sjogren syndrome, or the use of certain drugs.
Type 2 RTA, or proximal renal tubular acidosis,
happens when the damage or defect is relatively close to the start of the tubule.
Proximal RTA mostly happens in infants and usually is related to a disorder called
Fanconi's syndrome. Vitamin D deficiency, fructose intolerance, the use of certain
drugs, and some diseases also can cause proximal RTA.
Type 3 RTA is a combination of distal RTA and proximal RTA and
is rarely used as a classification anymore.
Type 4 RTA, or hyperkalemic renal tubular acidosis,
is caused by a transport disorder in the distal tubule. Transport involves the movement
of electrolytes such as sodium, chloride, and potassium between the blood and body
parts. When this process is abnormal, it can cause too much potassium to build up
in the blood (hyperkalemia).
This can be a problem for the heart and other organs. Hyperkalemic RTA can be caused
by urinary tract infections
(UTIs), autoimmune disorders, sickle cell disease, diabetes, kidney transplant
rejection, or the use of certain drugs.
A lot of the time, kids with RTA don't have any symptoms and may not know they
have the disease until it shows up on a blood or urine test.
For some kids, the first symptom of RTA is kidney stones, which can cause symptoms
pain in the back or side that spreads to the lower abdomen
pain while urinating
pee that is red, brown, or cloudy
frequent urge to urinate
nausea and vomiting
Over time, RTA can affect bone development and keep a child from growing as much
as he or she should. This is often why doctors suspect RTA in the first place.
Other symptoms of RTA you might notice include:
confusion, decreased alertness, or fatigue
increased breathing and heart rates
muscle cramps and pain in the back and abdomen
rickets (a disorder that can cause bone pain and skeletal and dental deformities)
If your child shows any symptoms of RTA, see a doctor right away. The sooner something
is done about the condition, the more effective treatment will be.
To diagnose RTA, the doctor will do a physical examination and take a sample of
your child's blood for testing. He or she also may want a urine sample. If test results
suggest that your child might have RTA, the doctor will work with you to decide the
best way to treat it.
How RTA is treated depends on what's causing it. If it's a reaction to a certain
drug, treatment may involve stopping use of the drug or changing the dosage. If an
underlying disease or other condition is causing RTA, it will be treated until that
To treat the effects of RTA, it's necessary to restore a normal acid level to the
blood. To do this, doctors prescribe alkaline medicines, such as sodium bicarbonate,
that help to lower the blood's concentration of acid.
Most of the time, treatment for RTA is effective. Kids whose RTA is caused by a
genetic defect may need treatment for the rest of their lives. The good news is that
sticking with their treatments lets kids remain healthy./p>