Renal Tubular Acidosis is a medical condition. When the kidney is unable to acidify urine, it leads to the accumulation of acid in the body. Usually, when blood is filtered by the kidney, it passes through the tubules of the nephrons (the functional unit of the kidney).
Before it flows into the bladder from the kidney, the urine undergoes an exchange of salts, acids and other solutes. Renal tubular acidosis results in the formation of excessive amounts of acid because the kidneys cannot drain them. This may happen because the kidneys cannot reabsorb the alkaline bicarbonate ions from the urine in the early segment of the nephron or because of inadequate production of acidic hydrogen ions in the latter half of the nephron.
Renal Tubular Acidosis is simply associated with abnormal urinary acidification. Other functions of the kidneys remain unimpaired.
There are several different types of renal tubular acidosis-
• Distal Renal Tubular Acidosis (RTA)
This is the most fundamental form of RTA. It is characterized when the hydrogen ions are not secreted into the lumen of the nephron by the alpha-intercalated cells of the medullary collective duct of the distal nephron. When this happens the pH of urine cannot be brought down below 5.3. Renal excretion is inhibited and hydrogen ions are not eliminated which leads to academia. At the same time, Potassium ions cannot be absorbed by the cell which leads to hypokalemia. The end result is protein retention and potassium excretion. Distal RTA can lead to the urinary stone formation, calcium deposits in the kidney, rickets and osteomalacia and Sjogren’s syndrome.
• Proximal RTA
When proximal tubular cells reabsorb 85% of filtered bicarbonates and 60% of filtered sodium from the urine, then this again leads to academia. The distal intercalated cells, however, function normally and so the academia is not as severe as in case of Distal RTA. The alpha-intercalated cells can acidify urine to a pH of 5.3 or less because they produce hydrogen ions. Proximal RTA is also associated with Fanconi Syndrome which is characterized by aminoaciduria, uricosuria, glucosuria, and tubular proteinuria.
• Combined distal and proximal RTA
Inherited carbonic anhydrase II deficit leads to combined distal and proximal RTA. This is accompanied by osteopetrosis, cerebral calcification, and renal tubular acidosis. Cases of combined distal and proximal RTA are very rare.
How is RTA understood?
The following steps are applied to analyze Renal Tubular Acidosis-
• Determining the anion gap in acidosis. The normal Anion Gap is 8-12 (4-6 mEq/L)
• Separating the renal from the extrarenal causes of normal anion gap acidosis
• Classifying the types of RTA
• If it is distal RTA, further tests will be necessary to support the diagnosis
How is RTA diagnosed?
Three types of tests can reveal if a person is affected by Renal Tubular Acidosis-
• Urine test
• Acid load test
• Physical examination
Treatment of RTA-
Doctors prescribe either or both of the following two types of therapies-
• Alkali therapy- The pH level of urine is restored and electrolytes are balanced
• Vitamin D supplements- If RTA leads to bone deformities or rickets, your doctor will prescribe vitamins and supplements for bones
Timely diagnosis can prevent the effects of Renal tubular Acidosis from becoming compounded. With the right medication, a person can lead a healthy normal life.