Renal tubular acidosis, or RTA, prevents the kidneys from excreting acid, which then builds up in the blood stream causing acidosis. During the body's metabolic processes, acid is created. The kidneys excrete this excess acid in its tubules, the microscopic tubes where acid and fluid exchange occurs. As a result of RTA, the levels of potassium, an important element in kidney fluid exchange, can be affected.
Types
There are four types of RTA, type 1 to 4, depending on what causes the acidosis, although type 3 is extremely rare and not very well defined. Type 1 is called distal RTA, because the problem occurs in the distal tubule, or the part of the tubule farthest away from the point where fluid from the blood enters the tubule. Type 2 is called proximal RTA, since the problem is closer to the point of entry of fluid into the tubule. Type 4 is called hyperkalemic RTA because contrary to the other types, it causes elevation, not decrease, of the potassium level.
Causes
According to the Merck Manual of Medical Information, type 1 may be inherited, caused by certain drugs, or related to certain autoimmune conditions such as lupus. Type 2 RTA is usually associated with an inherited condition like Fanconi's syndrome, which results in abnormal excretion of sugars, amino acids and substances like potassium. Type 4 RTA is not inherited, and is associated with diabetes, autoimmune conditions and certain medications.
General Symptoms
The symptoms of RTA can vary from mild, early on in the disease, to severe as the disease progresses. According to the National Kidney and Urologic Diseases Information Clearinghouse, children with RTA and long-term acidosis without correction can suffer from growth retardation, kidney stones, chronic kidney disease with eventual kidney failure. Other symptoms include muscle weakness and weak and painful bones.
Symptoms of Abnormal Potassium Levels
Low potassium, or hypokalemia, from type 1 and 2 RTA can result in muscle cramps and weakness, fatigue, constipation and abnormal heart rhythms. High potassium level, or hyperkalemia, which is associated with type 4 RTA, can also result in muscle weakness with potential muscle paralysis. Hyperkalemia can result in ventricular fibrillation, an abnormal quivering of the heart that can impair its ability to pump blood. Ventricular fibrillation is a life-threatening abnormal heart rhythm.
Treatment
The treatment of RTA depends on the type. Types 1 and 2 respond to sodium bicarbonate, or baking soda, which helps neutralize the acid in the blood. People with type 4 may not need bicarbonate, but usually need medicines to decrease the levels of potassium in the blood stream, a low potassium diet and plenty of fluids to prevent dehydration.
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