Renal Tubular 

Acidosis 

National Kidney and Urologic Diseases Information Clearinghouse 

National 

Institute of 

Diabetes and 

Digestive 

and Kidney 

Diseases 

NATIONAL 

INSTITUTES 

OF HEALTH 

Your body’s cells use chemical reactions 

to carry out tasks such as turning food 

into energy and repairing tissue. These 

chemical reactions generate acids. But 

too much acid in the blood—acidosis—can 

disturb many bodily functions. Healthy 

kidneys help maintain acid-base balance by 

excreting acids into the urine and returning 

bicarbonate—an alkaline, or base, substance—to the blood. This “reclaimed” 

bicarbonate neutralizes much of the acid 

that is created when food is broken down 

in the body. 

Renal tubular acidosis (RTA) is a disease 

that occurs when the kidneys fail to excrete 

acids into the urine, which causes a person’s blood to remain too acidic. Without 

proper treatment, chronic acidity of the 

blood leads to growth retardation, kidney 

stones, bone disease, and progressive renal 

failure. 

One researcher, pediatric neurologist 

Donald Lewis, has theorized that Charles 

Dickens may have been describing a child 

with RTA when he created the character of 

Tiny Tim in his famous story, “A Christmas 

Carol.” Tiny Tim’s small stature, malformed limbs, and periods of weakness are 

all possible consequences of the chemical 

imbalance caused by RTA. Among the evidence cited to support this theory is the fact 

that Tiny Tim’s condition, while fatal in one 

scenario, is reversible when Scrooge pays 

for medical treatments, which in those 

times would likely have included sodium 

bicarbonate and sodium citrate, which are 

alkaline agents that would neutralize the 

acid in Tiny Tim’s blood. Whether the 

literary diagnosis of Tiny Tim is correct 

or not, the good news is that medical 

treatment can indeed reverse the effects 

of RTA. 

Diagnosis 

To diagnose RTA, your doctor will check 

the acid-base balance in samples of your 

blood and urine. If the blood is more acidic 

than it should be and the urine less acidic 

than it should be, RTA may be the reason, 

but additional information is needed first to 

rule out other causes. If RTA is suspected, 

additional information about the sodium, 

potassium, and chloride levels in the urine 

and the potassium level in the blood will 

help identify which of the three types of 

RTA you have. In all cases, the first goal of 

therapy is to neutralize acid in the blood, 

but different treatments may be needed to 

address the different underlying causes of 

acidosis. 

U.S. Department 

of Health and 

Human Services 
Types of RTA 

At one time, doctors divided RTA into four 

types. 

•	 Type 1 is also called classic distal RTA. 

“Distal,” which means distant, refers 

to the point in the urine-forming tube 

where the defect occurs. It is relatively 

distant from the point where fluid 

from the blood enters the tiny tube, 

or tubule, that collects fluid and wastes 

to form urine. 

•	 Type 2 is called proximal RTA. The 

word “proximal,” which means near, 

indicates that the defect is closer to the 

point where fluid and wastes from the 

blood enter the tubule. 

•	 Type 3 is rarely used as a classification 

today because it is now thought to be 

a combination of type 1 and type 2. 

•	 Type 4 RTA is caused by another 

defect in the distal tubule, but it is 

different from classic distal RTA and 

proximal RTA because it results in 

high levels of potassium in the blood 

instead of low levels. Either low 

potassium (hypokalemia) or high 

potassium (hyperkalemia) can be 

a problem because potassium is 

important in regulating heart rate. 

Type 1: Classic Distal RTA 

This disorder may be inherited as a primary 

disorder or may be one symptom of a disease that affects many parts of the body. 

Researchers have now discovered the 

abnormal gene responsible for the inherited form. More often, however, classic 

distal RTA is a complication of diseases 

that affect many organ systems (systemic 

diseases), like the autoimmune disorders 

Sjögren’s syndrome and lupus. 

Other diseases and conditions associated 

with distal RTA include hyperparathyroidism, a hereditary form of deafness, 

analgesic nephropathy, rejection of a 

transplanted kidney, renal medullary 

cystic disease, obstructive uropathy, 

and chronic urinary tract infections. 

A major consequence of classic distal RTA 

is low blood-potassium. The level drops if 

the kidneys excrete potassium into urine 

instead of returning it to the blood supply. 

Since potassium helps regulate nerve and 

muscle health and heart rate, low levels 

can cause extreme weakness, cardiac 

arrhythmias, paralysis, and even death. 

Untreated distal RTA causes growth retardation in children and progressive renal 

and bone disease in adults. Restoring normal growth and preventing kidney stones, 

another common problem in this disorder, 

are the major goals of therapy. If acidosis 

is corrected with sodium bicarbonate or 

sodium citrate, then low blood-potassium, 

salt depletion, and calcium leakage into 

urine will be corrected. Alkali therapy 

also helps decrease the development of 

kidney stones. Potassium supplements are 

rarely needed except in infants, since alkali 

therapy prevents the kidney from excreting 

potassium into the urine. 

Type 2: Proximal RTA 

This form of RTA occurs most frequently 

in children as part of a disorder called 

Fanconi’s syndrome. The symptoms of 

Fanconi’s syndrome include high levels of 

glucose, amino acids, citrate, and phosphate in the urine, as well as vitamin D 

deficiency and low blood-potassium. 

Proximal RTA can also result from inherited disorders that disrupt the body’s normal 

breakdown and use of nutrients. Examples 

include the rare disease cystinosis (in which 

2	 Renal Tubular Acidosis 
cystine crystals are deposited in bones and 

other tissues), hereditary fructose intolerance, and Wilson’s disease. 

Proximal RTA also occurs in patients 

treated with ifosfamide, a drug used in 

chemotherapy. A few older drugs—such as 

acetazolamide or outdated tetracycline— 

can also cause proximal RTA. In adults, 

proximal RTA may complicate diseases 

like multiple myeloma, or it may occur in 

people who experience chronic rejection 

of a transplanted kidney. 

When possible, identifying and correcting 

the underlying causes are important steps 

in treating the acquired forms of proximal 

RTA. The diagnosis is based on the chemical analysis of blood and urine samples. 

Children with this disorder would likely 

receive large doses of oral alkali, such as 

sodium bicarbonate or potassium citrate, to 

treat acidosis and prevent bone disorders, 

kidney stones, and growth failure. Correcting acidosis and low potassium levels 

restores normal growth patterns, allowing 

bone to mature while preventing further 

renal disease. Vitamin D supplements 

may also be needed to help prevent bone 

problems. 

Type 4: Hyperkalemic RTA 

This form of RTA is most often referred 

to as type 4. It occurs when blood levels 

of the hormone aldosterone are low or 

when the kidneys do not respond to it. 

Aldosterone directs the kidneys to 

regulate the levels of sodium, potassium, 

and chloride in the blood. Type 4 RTA is 

distinguished by a high blood-potassium 

level. 

Hyperkalemic distal RTA may result from 

sickle cell disease, urinary tract obstruction, 

lupus, amyloidosis, or transplantation. 

Aldosterone’s action may be impeded by 

drugs, including 

•	 diuretics used to treat congestive heart 

failure such as spironolactone or 

eplerenone 

•	 blood pressure drugs called 

angiotensin-converting enzyme (ACE) 

inhibitors and angiotensin receptor 

blockers (ARBs) 

•	 the antibiotic trimethoprim 

•	 an agent called heparin that keeps


blood from clotting


•	 the antibiotic pentamidine, which is 

used used to treat pneumonia 

•	 a class of painkillers called


nonsteroidal anti-inflammatory


drugs (NSAIDs)


•	 some immunosuppressive drugs used 

to prevent transplant rejection 

For people who produce aldosterone but 

cannot use it, researchers have now identified the genetic basis for their body’s resistance to the hormone. To treat type 4 RTA 

successfully, patients may require alkaline 

agents to correct acidosis as well as medication to lower the potassium in their blood. 

If treated early, most people with RTA 

will not develop permanent kidney failure. 

Therefore, the goal is early recognition 

and adequate therapy, which will need to 

be maintained and monitored throughout 

the patient’s lifetime. 

3	 Renal Tubular Acidosis 
Hope Through Research 

The National Institute of Diabetes and 

Digestive and Kidney Diseases (NIDDK) 

conducts and supports research into many 

kinds of kidney disease, including renal 

tubular acidosis. NIDDK-supported 

researchers are exploring the genetic 

and molecular mechanisms that control 

acid-base regulation in the kidney. These 

studies will point the way to more effective 

treatments for RTA. 

For More Information 

American Association of Kidney Patients 

3505 East Frontage Road 

Suite 315 

Tampa, FL 33607 

Phone: 1–800–749–2257 or 813–636–8100 

Fax: 813–636–8122 

Email: info@aakp.org 

Internet: www.aakp.org 

American Kidney Fund 

6110 Executive Boulevard 

Suite 1010 

Rockville, MD 20852 

Phone: 1–800–638–8299 or 301–881–3052 

Email: helpline@akfinc.org 

Internet: www.kidneyfund.org 

National Kidney Foundation 

30 East 33rd Street 

New York, NY 10016 

Phone: 1–800–622–9010 or 212–889–2210 

Fax: 212–689–9261 

Email: info@kidney.org 

Internet: www.kidney.org 

National Kidney and 

Urologic Diseases 

Information Clearinghouse 

3 Information Way


Bethesda, MD 20892–3580


Phone: 1–800–891–5390


Fax: 703–738–4929


Email: nkudic@info.niddk.nih.gov


Internet: www.kidney.niddk.nih.gov


The National Kidney and Urologic Diseases 

Information Clearinghouse (NKUDIC) is a 

service of the National Institute of Diabetes 

and Digestive and Kidney Diseases (NIDDK). 

The NIDDK is part of the National Institutes 

of Health under the U.S. Department of Health 

and Human Services. Established in 1987, the 

Clearinghouse provides information about diseases of the kidneys and urologic system to 

people with kidney and urologic disorders and 

to their families, health care professionals, and 

the public. The NKUDIC answers inquiries, 

develops and distributes publications, and 

works closely with professional and patient 

organizations and Government agencies to 

coordinate resources about kidney and urologic 

diseases. 

Publications produced by the Clearinghouse are 

carefully reviewed by both NIDDK scientists 

and outside experts. 

This publication is not copyrighted. The 

Clearinghouse encourages users of this fact 

sheet to duplicate and distribute as many 

copies as desired. 

This fact sheet is also available at 

www.kidney.niddk.nih.gov. 

U.S. DEPARTMENT OF HEALTH 

AND HUMAN SERVICES 

National Institutes of Health 

NIH Publication No. 05–4696 

August 2005