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Distal renal tubular acidosis

Definition

Distal renal tubular acidosis is a disease that occurs when the kidneys don't remove acid properly into the urine, leaving the blood too acidic (called acidosis).

Alternative Names

Renal tubular acidosis - distal; Renal tubular acidosis type I; Type I RTA; RTA - distal; Classical RTA

Causes, incidence, and risk factors

Your kidneys normally regulate your body's pH by removing acids from the blood and discarding them into the urine.

Distal renal tubular acidosis (Type I RTA) is caused by a defect in the kidney tubes that causes acid to build up in the bloodstream.

Type I RTA is caused by a variety of conditions, including:

• Amyloidosis
• Fabry disease
• Sickle cell disease
• Sjogren syndrome
• Systemic lupus erythematosus
• Wilson disease
• Use of certain drugs such as amphotericin B, lithium, and analgesics

Symptoms

• Confusion or decreased alertness
• Fatigue
• Impaired growth
• Increased breathing rate
• Kidney stones
• Nephrocalcinosis
• Osteomalacia
• Rickets
• Muscle weakness

Other symptoms can include:

• Bone pain
• Decreased urine output
• Increased heart rate or irregular heartbeat
• Muscle cramps
• Pain in the back, flank, or abdomen
• Skeletal abnormalities

Signs and tests

Arterial blood gas and blood chemistries may suggest metabolic acidosis or electrolyte imbalances, most often low levels of potassium or bicarbonate.

Other tests that may be done include:

• Urine pH, usually greater than 5.0 in patients with this condition
• Urinalysis may show increased levels of calcium and potassium

Treatment

The goal is to restore the normal pH (acid-base level) and electrolyte balance. This will indirectly correct bone disorders and reduce the risk of calcium buildup in the kidneys (nephrocalcinosis) and kidney stones. The underlying cause should be corrected if it can be identified.

Alkaline medications such as potassium citrate and sodium bicarbonate correct the acidic condition of the body. Sodium bicarbonate may correct the loss of potassium and calcium.

Vitamin D and calcium supplements are usually not given because there may be calcium deposits in the kidneys, even after bicarbonate therapy.

Support Groups

Expectations (prognosis)

The disorder must be treated to reduce its effects and complications, which can be permanent or life-threatening. Most cases get better with treatment.

Complications

• Osteomalacia
• Rickets
• Nephrocalcinosis
• Kidney stones
• Electrolyte imbalances, such as low blood potassium level

Calling your health care provider

Call your health care provider if you have symptoms of distal renal tubular acidosis.

Get help immediately if you develop emergency symptoms, such as:

• Decreased consciousness
• Seizures
• Severe decrease in alertness or orientation

Prevention

There is no prevention for this disorder.

References

Seifter JL. Acid-base disorders. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 119.