In renal tubular acidosis, the kidney tubules malfunction, resulting in excess levels of acid in the blood.
The tubules of the kidneys that remove acid from the blood are damaged when a person takes certain medications 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.
Some people drink a solution of baking soda every day to neutralize the acid.
(See also Introduction to Disorders of Kidney Tubules.)
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. In renal tubular acidosis, the kidney tubules malfunction in 1 of 2 ways that tend to increase acids in the blood (metabolic acidosis):
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
Calcium deposits in the kidneys, which may lead to kidney stones
Painful softening and bending of the bones (osteomalacia or rickets)
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, sickle cell disease, or an autoimmune disorder (such as systemic lupus erythematosus). Renal tubular acidosis may also be a temporary condition brought on by blockage of the urinary tract
If renal tubular acidosis persists, it may damage the kidney tubules and progress to chronic kidney disease.
There are 4 types of renal tubular acidosis, types 1 through 4. The types are distinguished by the particular abnormality in kidney function that causes acidosis. All 4 types are uncommon, but type 4 is the most common and type 3 is extremely rare and therefore is not discussed here.
Some Types of Renal Tubular Acidosis
Type | Cause | Underlying Abnormality | Resulting Symptoms and Metabolic Abnormalities |
|---|---|---|---|
1 | May be hereditary or may be triggered by an autoimmune disorder or certain medications Cause usually not known, especially in women | Inability to excrete acid into the urine | High blood acidity Mild dehydration Low potassium levels in the blood, leading to muscle weakness and paralysis Fragile bones Bone pain Calcium deposits, leading to kidney stones |
2 | Usually caused by a hereditary disease such as Fanconi syndrome, hereditary fructose intolerance, Wilson disease, or oculocerebrorenal syndrome (Lowe syndrome) May also be caused by multiple myeloma, heavy metal poisoning, or certain medications | Inability to reabsorb bicarbonate from the urine, so too much bicarbonate is excreted | High blood acidity Fragile bones Bone pain Mild dehydration Low potassium levels in the blood Decreased production of the active form of vitamin D |
4 | Not hereditary Caused by diabetes, an autoimmune disorder, chronic kidney disease, or an obstruction in the urinary tract | Deficiency of or inability to respond to aldosterone, a hormone that helps regulate potassium and sodium excretion by the kidneys | Mildly increased blood acidity and high potassium levels in the blood that rarely cause symptoms, unless the potassium level is unusually high (in that case, irregular heartbeats and muscle paralysis develop) |
Note: Type 3 is a mixture of Types 1 and 2 and is extremely rare. | |||
Symptoms of Renal Tubular Acidosis
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 may develop, causing damage to kidney cells and, in some cases, chronic kidney disease. In type 2 and sometimes in type 1, bone pain and osteomalacia may occur in adults and rickets may occur in children.
Type 4
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 Renal Tubular Acidosis
Blood tests
Urine tests
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 Renal Tubular Acidosis
Treatment depends on the type.
Types 1 and 2
Type 4
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 medications or adjusting their dosages.
More Information
The following English-language resource 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): Provides insight into ongoing research, consumer health information in English and Spanish, a blog, and community health and outreach programs.
