The tubules of the kidneys that remove acid from the blood are damaged when a person takes certain drugs or has another disorder that affects the kidneys.
Often muscle weakness and diminished reflexes occur when the disorder has been present for a long time.
Blood tests show high acid levels and a disturbance of the body's acid-base balance. Overview of Acid-Base Balance An important property of blood is its degree of acidity or alkalinity. The acidity or alkalinity of any solution, including blood, is indicated on the pH scale. The pH scale, ranges from 0 ... read more
Some people drink a solution of baking soda every day to neutralize the acid.
(See also Introduction to Disorders of Kidney Tubules Introduction to Disorders of Kidney Tubules The kidneys filter and cleanse the blood. They also maintain the body’s balance of water, electrolytes (such as sodium, potassium, bicarbonate, and chloride), and nutrients in the blood. The... read more .)
To function normally, body acids and alkalis (such as bicarbonate) must be balanced. Normally, the breakdown of food produces acids that circulate in the blood. The kidneys remove acids from the blood and excrete them in the urine. This function is predominantly carried out by the kidney tubules Introduction to Disorders of Kidney Tubules The kidneys filter and cleanse the blood. They also maintain the body’s balance of water, electrolytes (such as sodium, potassium, bicarbonate, and chloride), and nutrients in the blood. The... read more . In renal tubular acidosis, the kidney tubules malfunction in one of two ways that tend to increase acids in the blood (metabolic acidosis Acidosis Acidosis is caused by an overproduction of acid that builds up in the blood or an excessive loss of bicarbonate from the blood (metabolic acidosis) or by a buildup of carbon dioxide in the blood... read more ):
Too little of the acids the body produces are excreted, so acid levels in blood increase.
Too little of the bicarbonate that filters through the kidney tubules is reabsorbed, so too much bicarbonate is lost in the urine.
In renal tubular acidosis, the balance of electrolytes is also affected. Renal tubular acidosis may lead to the following problems:
Low or high potassium levels in the blood
Painful softening and bending of the bones (osteomalacia or rickets Hypophosphatemic Rickets Hypophosphatemic rickets is a disorder in which the bones become painfully soft and bend easily because the blood contains low levels of the electrolyte phosphate. (See also Introduction to... read more )
Renal tubular acidosis may be a permanent, inherited disorder in children. However, it may be an intermittent problem in people who have other disorders, such as diabetes mellitus Diabetes Mellitus (DM) Diabetes mellitus is a disorder in which the body does not produce enough or respond normally to insulin, causing blood sugar (glucose) levels to be abnormally high. Urination and thirst are... read more , sickle cell disease Sickle Cell Disease Sickle cell disease is an inherited genetic abnormality of hemoglobin (the oxygen-carrying protein found in red blood cells) characterized by sickle (crescent)-shaped red blood cells and chronic... read more , or an autoimmune disorder (such as systemic lupus erythematosus Systemic Lupus Erythematosus (SLE) Systemic lupus erythematosus is a chronic autoimmune inflammatory connective tissue disorder that can involve joints, kidneys, skin, mucous membranes, and blood vessel walls. Problems in the... read more [SLE or lupus]). Renal tubular acidosis may also be a temporary condition brought on by blockage of the urinary tract Urinary Tract Obstruction Urinary tract obstruction is a blockage that inhibits the flow of urine through its normal path (the urinary tract), including the kidneys, ureters, bladder, and urethra. Blockage can be complete... read more or by drugs such as acetazolamide, amphotericin B, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers (ARBs), and diuretics that conserve the body’s potassium (so-called potassium-sparing diuretics).
If renal tubular acidosis persists, it may damage the kidney tubules and progress to chronic kidney disease Chronic Kidney Disease Chronic kidney disease is a slowly progressive (months to years) decline in the kidneys’ ability to filter metabolic waste products from the blood. Major causes are diabetes and high blood pressure... read more .
There are four types of renal tubular acidosis, types 1 through 4. The types are distinguished by the particular abnormality in kidney function that causes acidosis. All four types are uncommon, but type 4 is the most common and type 3 is extremely rare.
Symptoms of RTA
Many people have no symptoms. Most others develop symptoms only after the disorder has been present for a long time. Which symptoms eventually develop depend on the type of renal tubular acidosis.
Types 1 and 2
When potassium levels in the blood are low, as occurs in types 1 and 2, neurologic problems may develop, including muscle weakness, diminished reflexes, and even paralysis. In type 1, kidney stones Stones in the Urinary Tract Stones (calculi) are hard masses that form in the urinary tract and may cause pain, bleeding, or an infection or block of the flow of urine. Tiny stones may cause no symptoms, but larger stones... read more may develop, causing damage to kidney cells and, in some cases, chronic kidney disease Chronic Kidney Disease Chronic kidney disease is a slowly progressive (months to years) decline in the kidneys’ ability to filter metabolic waste products from the blood. Major causes are diabetes and high blood pressure... read more . In type 2 and sometimes in type 1, bone pain and osteomalacia may occur in adults and rickets may occur in children.
In type 4, potassium levels typically increase, although it is uncommon for the level to rise high enough to cause symptoms. If the level becomes too high, irregular heartbeats and muscle paralysis may develop.
Diagnosis of RTA
A doctor considers the diagnosis of type 1 or type 2 renal tubular acidosis when a person has certain characteristic symptoms (such as muscle weakness and diminished reflexes) and when tests reveal high levels of acid and low levels of bicarbonate and potassium in the blood.
Type 4 renal tubular acidosis is usually suspected when high potassium levels accompany high acid levels and low bicarbonate levels in the blood. Tests on urine samples and other tests help to determine the type of renal tubular acidosis.
Treatment of RTA
Drinking sodium bicarbonate daily
Treatment depends on the type.
Types 1 and 2
Types 1 and 2 are treated by drinking a solution of sodium bicarbonate (baking soda) every day to neutralize the acid that is produced from food. This treatment relieves the symptoms and prevents kidney failure and bone disease or keeps these problems from becoming worse. Other specially prepared solutions are available, and potassium supplements may also be required.
In type 4, the acidosis is so mild that bicarbonate may not be needed. High potassium levels in the blood can usually be kept in check by restricting potassium intake, avoiding dehydration, using diuretics that increase potassium loss, and substituting different drugs or adjusting drug dosages.
The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK): Insight into ongoing research, consumer health information in English and Spanish, a blog, and community health and outreach programs.