Renal Tubular Acidosis
Kidneys are constantly filtering your blood with thousands of tiny filters called glomeruli. The glomeruli know what should stay in your blood and what should pass through as urine. Kidneys also balance acid and alkali (base) in the body. The balance is called pH and all living things need an ideal level of pH. For example, fish in an aquarium can only stay healthy if they pH of the water is right.
Kidneys help your body maintain a proper pH level by getting rid of the acid through urine and keeping the right alkali levels. Too much acid in the body is called acidosis. If the kidneys are causing acidosis, it is because they are unable to keep the right pH balance in your body. This can occur if the part of the kidney (tubule) that is in charge of the acid and alkali balance is not working correctly.
Tubules are tiny drainage tubes. One is connected to each kidney filter. All the tubules in each kidney connect to a larger drainage tube called the ureter, which connects to the bladder. Urine drains into the bladder, and collects there until you empty it. Since the problem in the tubules makes the body too acidic (acidosis) and the tubules are in the kidneys (renal is Latin for kidney), the name of the problem is called Renal Tubular Acidosis (RTA).
The main reason that doctors look for RTA in kids is poor growth. Kids need the right body pH to grow well. Your doctor can order the tests needed to see if RTA is the cause of poor growth. If RTA is the cause, your doctor can get advice from a pediatric kidney specialist called a pediatric nephrologist.
RTA is found by measuring the bicarbonate in the blood. Bicarbonate is the alkali that balances body acid. If bicarbonate is too low, the body needs more to balance body acid. Once it is known that the bicarbonate is low, then the cause must be found. Some rare diseases can cause it, but in those diseases other things will also be wrong. If the kidneys are the cause, then you r doctor consults a pediatric nephrologist. There are blood tests that help separate the rare causes from the more common ones.
When the kidneys are the problem, it is called RTA as stated above. The most common type of RTA is due to the very young kidney not being able to keep bicarbonate from leaking out into the urine. This will get better with age, usually age two-five years old. Until then, a child with RTA takes a medicine to replace the bicarbonate and keep the blood level right so that the right pH is made, then growth can improve. It is not always necessary to see a pediatric nephrologist if the pediatrician has talked with the nephrologist and simple RTA is the problem. There are rare forms of RTA that are more complicated, but the nephrologist working with your doctor can help sort things out.
Bicitra or Polycitra are some medicines the body can tum into bicarbonate. Enough must be taken to increase the bicarbonate in blood. The dose is adjusted until the blood test shows a level of at least 20. At this level growth should be fine (unless other problems that cause poor growth are present). The blood tests will also show when the RTA is gone.