Renal Tubular Acidosis

In renal tubular acidosis (REEN-uhl TOO-byuh-ler as-i-DOH-sis), your kidneys can’t remove excess acid and acid waste products from your blood.

Your kidneys have many jobs. One of them is to regulate your body pH. Your body pH measures the levels of acids and bases (alkaline) in your body. It’s very important to the way your body system functions. Typically, the pH range is between 7.35 and 7.45. A body pH below this range means it’s acidic. A body pH above this range means it’s basic (alkaline).

For example, if you eat a meal that has a lot of protein, your body will produce a lot of acids. Your kidneys must get rid of these excess acids to keep your pH at a normal range. If you eat a meal that has a lot of fruits and vegetables, your body will have a lot of bases. Your kidneys must get rid of the excess bases to maintain your body pH.

Too much acid in your blood and other body fluids and tissues will change your normal body pH. This can affect many body system functions, like breathing. It may be life-threatening without treatment.

Renal tubular acidosis (RTA) is rare. Healthcare providers may misdiagnose or underdiagnose it because they don’t know much about it. This makes it difficult to estimate how many people have RTA.

Types of renal tubular acidosis

Healthcare providers classify renal tubular acidosis into three main types. These types depend on what part of the renal tubule has a problem:

• Type 1 RTA (distal RTA or dRTA): This is when damage prevents the far (distal) parts of the kidney tubules from being able to get rid of acid.
• Type 2 RTA (proximal RTA or pRTA): This is when damage prevents the closer (proximal) parts of the kidney tubules from being able to get rid of acid. Type 2 RTA is rarer than type 1 RTA. It’s most likely to occur during infancy. But it may also relate to alcohol use disorder, multiple myeloma and genetic causes.
• Type 4 RTA (hyperkalemic RTA): This is when a problem occurs at the end part of the tubules. Your kidney tubules can’t get rid of enough potassium (hyperkalemia) and acid. Hyperkalemia also affects your kidneys’ ability to filter acid from your blood. Type 4 RTA is the most common type. It may occur if you have diabetes or if you take some medications.

Type 3 RTA is a combination of distal and proximal RTA. It’s very rare. Healthcare providers don’t typically use it to classify RTA.

Symptoms of renal tubular acidosis

Renal tubular acidosis symptoms develop due to high acid levels. They affect how many of your organ systems work. Symptoms may include:

• Bone pain
• Breathing quickly (tachypnea)
• Confusion
• Dehydration
• Feeling very tired (fatigue)
• Increased heartbeat (tachycardia) or irregular heartbeat (atrial arrhythmia)
• Muscle weakness
• Pain, especially in your abdomen, back and flank
• Peeing less than usual (oliguria)
• Softening and weakening of bones (osteomalacia)

What is the most common cause of RTA?

Renal tubular acidosis causes depend on the type you have.

Type 1 RTA

You may inherit distal RTA from a biological parent (genetic disorder). You may also develop it from an autoimmune disease or certain medications.

• Autoimmune diseases: Examples include rheumatoid arthritis (RA), Sjögren’s syndrome and systemic lupus erythematosus (lupus).
• Genetic disorder: Your SLC4A1, ATP6V0A4 and AT6V1B1 genes help balance the acids and bases in your body. Genetic variations in these genes can cause type 1 RTA.
• Medications: The antifungal medication amphotericin B, the psychiatric medication lithium and antibiotics such as pentamidine may cause type 1 RTA.

The most common cause of type 1 RTA in adults is autoimmune diseases.

Type 2 RTA

Proximal renal tubular acidosis causes vary. You may inherit type 2 RTA from a biological parent. Or another inherited condition may cause it. These include:

• Amyloidosis
• Cystinosis
• Fanconi syndrome
• Hereditary fructose (fruit sugar) intolerance
• Light chain monoclonal gammopathy of renal significance
• Multiple myeloma
• Wilson disease

Certain medications may also cause RTA type 2. These medications treat the following conditions:

• Glaucoma
• HIV
• Migraine headaches
• Seizures
• Viral hepatitis

Exposure to heavy metals, including lead and cadmium, can also cause type 2 RTA.

Some of the most common causes of type 2 RTA in adults include amyloidosis, light chain monoclonal gammopathy of renal significance and multiple myeloma.

Type 4 RTA

Hyperkalemic RTA can occur when inherited or acquired conditions affect your kidneys. These may include:

• Addison’s disease
• Amyloidosis
• Diabetes-related nephropathy
• A genetic variation that helps regulate your blood pressure (Gordon’s syndrome)
• HIV/AIDS
• Kidney transplant rejection
• Lupus
• Sickle cell disease
• Urinary system obstruction, like an enlarged prostate gland (benign prostatic hyperplasia), kidney stone or tumor

It can also occur when there are low levels of aldosterone in your blood. Aldosterone is a hormone that helps your kidneys regulate your sodium (salt) levels. This can also affect your blood potassium levels.

Drugs that may cause type 4 RTA include:

• Blood thinners (anticoagulants)
• Certain antibiotics
• Certain blood pressure medications, including ACE inhibitors and ARBs
• Certain immunosuppressants that help prevent transplanted organ rejection
• Diuretics
• Nonsteroidal anti-inflammatory drugs (NSAIDs)

The most common cause of type 4 RTA in adults is diabetes-related nephropathy.

Risk factors

Renal tubular acidosis is rare. But your chances of developing RTA increase if you:

• Have a blockage (obstruction) in your urinary system
• Have certain autoimmune diseases, including Fanconi syndrome, lupus or Sjögren’s syndrome
• Have exposure to cadmium or lead
• Inherit certain genes from your biological parents
• Receive a kidney transplant
• Take certain medications

Complications of renal tubular acidosis

Complications may vary according to the type of renal tubular acidosis you have.

Type 1 RTA complications may include:

• Calcium buildup in your kidneys, which may cause kidney stones
• Chronic kidney disease (CKD)
• Growth delays in children (growth faltering)
• Hearing loss (renal tubular acidosis with deafness)
• Metabolic bone disease
• Sickle cell anemia
• UTIs
• Weak connective tissues (Ehlers-Danlos syndrome)

Type 2 RTA complications may include:

• Growth delays in children
• Problems with your teeth
• Soft bones, which make them more likely to bend or break (rickets)

Type 4 RTA complications may include:

• Electrical issues with your heart (cardiac arrest) due to high potassium levels
• Irregular heartbeat
• Muscle weakness

Without treatment, each type of RTA can be fatal.

How doctors diagnose renal tubular acidosis

A healthcare provider will likely:

• Review your medical history
• Ask questions about your symptoms
• Perform a physical exam

If they think you have RTA, they may recommend blood tests and urine tests (urinalyses). They use these tests to measure your pH and potassium levels. They may recommend other tests depending on the possible cause.

How is it treated?

It depends on what type you have. It also depends on whether the cause is inherited or acquired. Providers will give you a better idea of what to expect according to your specific diagnosis.

For each type of RTA, treatment usually involves oral alkali therapy (sodium bicarbonate or sodium citrate). This therapy can:

• Increase your blood pH (make it more basic)
• Relieve symptoms
• Help prevent bone diseases, kidney stones or kidney failure

The most common forms of oral alkali therapy are tablets. But they may also include a solution that you drink.

Other medications a provider may recommend include:

• Calcium and vitamin D supplements to help prevent bone diseases
• Potassium citrate replacement tablets to treat low potassium blood levels (hypokalemia)
• Thiazide diuretics (like hydrochlorothiazide or chlorthalidone) to help keep bicarbonate in your body and lower your risk of getting a calcium kidney stone

Providers may also recommend adjusting your eating patterns. This may include eating lots of fruits and veggies and cutting back on eating high-protein meats. They may recommend talking to a renal dietitian. Renal dietitians make meal plans for people who have kidney problems.

What kind of doctor treats this condition?

You may need a specialized team of healthcare providers to help treat renal tubular acidosis. Your care team may include a:

• Hearing specialist (audiologist)
• Kidney specialist (nephrologist)
• Musculoskeletal specialist (orthopaedist)

When should I see my healthcare provider?

Contact a healthcare provider right away if you have signs of renal tubular acidosis. Reach out again if your symptoms don’t start to improve after starting treatment.

You may wish to ask a provider the following questions:

• What caused renal tubular acidosis?
• What treatment do you recommend?
• What tests do you recommend?
• What can I do to feel better?
• What things do I need to avoid, and what lifestyle modifications do I need to follow?
• Are there any current medications I’m taking that may affect my RTA?
• When should I start feeling better?
• Do I need treatment for the rest of my life?
• Will my child have growth delays?
• Are there any RTA clinical studies I can participate in?

What is the prognosis for renal tubular acidosis?

It depends on the type of renal tubular acidosis you have and its cause. Alkali therapy typically helps treat your symptoms. But you may need it for the rest of your life, even if the underlying cause of RTA goes away. RTA also increases your chances of developing other serious medical conditions. These include bone diseases, heart problems, kidney failure and death. You may need regular testing to check your blood pH.

Healthcare providers will give you a better idea of what to expect.