Published: 18 Jun 2025

ICD9: 588.89      ICD10: N25.89      ICD11: GB90.44

Renal Tubular Acidosis (RTA) is a condition in which the kidneys fail to properly acidify the urine.
This failure leads to an accumulation of acid in the body (metabolic acidosis). In simpler terms, the kidneys aren't doing their job of removing acid from the body, resulting in an acid-base imbalance.

Here's a breakdown:

The Kidneys' Role in Acid-Base Balance: Healthy kidneys play a crucial role in maintaining the body's acid-base balance. They do this through several mechanisms:
Reabsorbing Bicarbonate: Bicarbonate is a base that helps neutralize acids. The kidneys reabsorb most of the bicarbonate filtered by the glomeruli, preventing it from being lost in the urine.
Excreting Acids: The kidneys excrete acids produced by the body's metabolism into the urine. They do this by:
Excreting Hydrogen Ions (H+): Specialized cells in the kidney tubules secrete H+ into the urine, which binds to buffers and is then eliminated.
Generating and Excreting Ammonium (NH4+): Ammonia is produced in the kidneys and combines with H+ to form ammonium, which is then excreted. This is a major mechanism for acid excretion.

What Happens in RTA: In RTA, these processes are disrupted, leading to:
Metabolic Acidosis: The body becomes too acidic.
Variable Electrolyte Imbalances: This can include low potassium (hypokalemia), low phosphate (hypophosphatemia), and high chloride (hyperchloremia).
Potential Complications: These imbalances can lead to a variety of problems.

Types of RTA:

RTA is classified into several types, each with a different underlying cause and mechanism:

Type 1 (Distal RTA): The kidneys cannot properly secrete acid (H+) into the urine in the distal tubule. This is the most common type in adults.
Type 2 (Proximal RTA): The kidneys cannot properly reabsorb bicarbonate in the proximal tubule. This leads to bicarbonate being lost in the urine.
Type 4 (Hyperkalemic RTA): This is often due to a deficiency or resistance to the hormone aldosterone. Aldosterone normally stimulates the kidneys to excrete potassium and acid. In Type 4 RTA, potassium excretion is impaired (leading to hyperkalemia), and acid secretion is also impaired.
Type 3: This type is extremely rare and often considered a variant of type 1 or 2. It is characterized by features of both.

Causes:

The causes of RTA vary depending on the type and can include:

Genetic Disorders: Some types of RTA are inherited.
Autoimmune Diseases: Lupus, Sjögren's syndrome.
Medications: Amphotericin B, ifosfamide, lithium, topiramate.
Kidney Diseases: Chronic kidney disease.
Urinary Tract Obstruction:
Multiple Myeloma:
Vitamin D Deficiency: (Especially in Type 2 RTA)

Symptoms:

Symptoms of RTA can vary depending on the severity and type, but may include:

Fatigue
Muscle Weakness
Bone Pain or Fractures: Chronic acidosis can lead to bone demineralization (osteomalacia or rickets).
Kidney Stones: Especially common in Type 1 RTA.
Growth Retardation (in children)
Failure to Thrive (in infants)
Heart Rhythm Problems (due to electrolyte imbalances)

Diagnosis:

Diagnosis of RTA involves:

Blood Tests: To measure electrolytes (sodium, potassium, chloride, bicarbonate), pH, and creatinine.
Urine Tests: To measure urine pH, electrolytes, and fractional excretion of bicarbonate.
Ammonium Chloride Loading Test: This test assesses the kidney's ability to acidify the urine in response to an acid load.
Genetic Testing: May be considered if a hereditary cause is suspected.

Treatment:

Treatment for RTA focuses on correcting the acid-base imbalance and addressing any underlying causes. This typically involves:

Bicarbonate Supplementation: To neutralize excess acid in the body.
Electrolyte Management: Addressing potassium, phosphate, and calcium imbalances.
Treating Underlying Conditions: Managing any autoimmune diseases or discontinuing medications that may be contributing to the problem.
Vitamin D supplementation: May be needed to correct rickets or osteomalacia.

In summary, RTA is a group of disorders that occur when the kidneys fail to properly regulate acid-base balance, leading to metabolic acidosis and potential complications. Understanding the specific type of RTA is crucial for effective diagnosis and management.

Disclaimer: This information is for general knowledge and informational purposes only, and does not constitute medical advice. It is essential to consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.