The kidneys filter waste materials from the blood and also help regulate the balance of acids and bases. If the kidneys become damaged, acid can build up in the body, resulting in a condition known as renal tubular acidosis. This disorder can affect children, resulting in multiple symptoms.
Types
There are three main kinds of renal tubular acidosis, according to the Department of Pediatrics at Miami University. The first two types are distinguished based on the location of the defect in the kidney tubule, which is the part of the kidney that collects wastes and fluid from the blood to make urine. Distal renal tubular acidosis, also known as type I, is caused by a defect that is relatively farther from, or distal to, where fluid and wastes from the blood enter the kidney tubule. Type II, also known as proximal renal tubular acidosis, is caused by a defect that occurs in a part of the tubule closer, or more proximal, to where the wastes and fluid enter. The other main kind of renal tubular acidosis, called hyperkalemic renal tubular acidosis, is also known as type IV; the problem that causes it is an electrolyte transport impairment in the distal part of the tubule, and it differs from the other types in that it is associated with high rather than low levels of potassium in the blood. Type III renal tubular acidosis is now believed to be a combination of types I and II.
Symptoms
Children who have renal tubular acidosis most commonly experience growth retardation, which is caused by poor bone growth. Other symptoms are due to changes in potassium levels; children with types I and II often experience muscle weakness and diminished reflexes as a result of low potassium levels. Children with type IV renal tubular acidosis, on the other hand, can develop an irregular heartbeat and muscle paralysis as a result of elevated potassium levels in the blood, the Merck Manual explains.
Causes
Renal tubular acidosis in children has many different causes. Most cases of type I disease are due to systemic problems, such as lupus or Sjogren's disease, although the National Institute of Diabetes and Digestive and Kidney Disorders reports that sickle cell anemia, hyperthyroidism and hyperparathyroidism can also cause this problem. Pediatric type II renal tubular acidosis is usually caused by Fanconi's syndrome, a hereditary condition that affects the excretion of citrate, phosphate, glucose and amino acids into the blood and also causes vitamin D deficiency. Hyperkalemic renal tubular acidosis can be due to a genetic defect or problems manufacturing or responding to aldosterone, a hormone that regulates kidney function. It may also occur as a side effect of certain drugs, including nonsteroidal anti-inflammatory agents and some antibiotics.
Diagnosis
Renal tubular acidosis is usually diagnosed via blood analysis. Patients with types I and II renal tubular acidosis typically have acidic blood with low levels of potassium; type IV is marked by elevated potassium and high quantities of acid.
Treatment
Children diagnosed with types I and II renal tubular acidosis need to ingest a bicarbonate solution each day; bicarbonate is a chemical which neutralizes acid and helps relieve the symptoms and prevent additional damage to the bones and kidneys. Potassium supplements may also be needed. Type IV renal tubular acidosis is usually treated by restricting the amount of potassium consumed each day and by avoiding medications that appear to trigger the condition.
