About Renal Tubular Acidosis in Children

Renal tubular acidosis, or RTA, is a series of disorders in which children present with an acid-base balance abnormality in their blood. The acid-base balance refers to the capacity of the kidneys to adjust the pH of the blood to maintain it as neutral as possible. Renal tubular acidosis tilts the balance toward acidic blood. This in turn can cause electrolyte abnormalities. RTA can be fatal in children if it goes unrecognized, so prompt recognition and diagnosis is important in order to institute appropriate treatment. Most cases of RTA are detected in childhood, as it is a congenital disorder.

Significance

• The kidney is mostly responsible for maintaining the acid-base balance in the blood. It does this by adjusting how much bicarbonate (base) or hydrogen (acid) it retains or excretes from the body. High pH is basic or alkalotic. Low pH is acidic. These processes take place at different levels inside the tubules of the kidney. In renal tubular acidosis, these mechanisms are affected, throwing off the delicate acid-base balance. There are several types of renal tubular acidosis, depending on which part of the kidney is affected.

Types

• In proximal RTA, there is a defect in the capacity of the proximal tubule of the kidneys to reabsorb bicarbonate. Bicarbonate is wasted in the urine, causing it to increase its pH. Eventually this process is reversed and you have both acidic blood and urine.

  In distal RTA, the kidney cannot excrete hydrogen, resulting in blood acidosis. Since hydrogen is not excreted, the urine cannot become acidic.

  Hyperkalemic RTA result of a defect in the function of the hormone aldosterone. Aldosterone stimulates the secretion of hydrogen, or acid. When this is impaired, acid build up in the blood. Aldosterone also helps to excrete potassium in the urine. When aldosterone doesn't work, potassium builds up in the blood, resulting in high potassium or hyperkalemia. This can cause significant cardiac rhythm abnormalities.

Effects

• As opposed to adults with the disease, who usually present with kidney stones, children with RTA present with poor weight gain or failure to thrive. Because the disease also affects the production and excretion of calcium, children can present with deposits of calcium in the kidneys, poor bone formation or rickets, and muscle weakness.

  Other symptoms include vomiting, listlessness, dehydration and increased thirst with behavior changes such as drinking more liquids than normal and repeated episodes of urination.

Diagnosis

• The diagnosis must be considered in all patients presenting with the typical symptoms. A blood test that measures serum electrolytes and acid-base balance can help pinpoint the type of RTA. Also, the urine pH in comparison with the blood pH helps establish the diagnosis.

Prevention/Solution

• Most cases of both child and adult RTA can be treated with life-long supplementation with alkalotic or basic compounds, which helps stabilize the pH in the blood. Sodium and potassium supplementation also can be required. Adults diagnosed with RTA tend to produce calcium deposits in their kidneys, causing stones and predisposing them to chronic renal insufficiency. Children, on the other hand, can avoid renal failure if treatment is instituted before the age of 2.