Treatment of distal (type 1) and proximal (type 2) renal tubular acidosis
Renal tubular acidosis (RTA) is a rare kidney disorder that results from the inability of the kidneys to excrete acids normally into the urine. Because of the inadequate removal of acids in the urine, their levels in the blood increase, giving rise to a condition called acidosis.
Renal tubular acidosis is of four types—
- Type 1 or distal renal tubular acidosis: the problem is at the distal part of the tubules.
- Type 2 or proximal renal tubular acidosis: the problem is at the proximal part of the tubules.
- Type 3 or mixed renal tubular acidosis
- Type 4 or hyperkalemic renal tubular acidosis: is characterised by the inability of the tubules to excrete enough potassium, which affects the ability of the kidney to excrete acid from the blood.
Treatment of proximal or type 2 renal tubular acidosis:
- The aim of treatment is to get control of the acid and electrolyte levels in the body and maintain their balance. This, in turn, helps prevent bone disorders and decreases the chances of developing osteopenia and osteomalacia in adult patients.
- Some adult patients recover without treatment. Alkaline medications such as sodium bicarbonate and potassium citrate are given to younger patients. It helps to keep bone diseases (that can develop due to excess acid) such as rickets in check and promotes normal growth.
- Oral bicarbonate replacement at 1-2 meq/kg per day with potassium citrate or sodium bicarbonate is required to correct metabolic acidosis. Treatment with potassium citrate is especially helpful for patients with nephrolithiasis, hypokalemia, or nephrocalcinosis.
- To treat type 2 renal tubular acidosis, higher doses of bicarbonate are required (>10 mmol/kg). Increasing the bicarbonate levels in the blood will raise the filtered bicarbonate load beyond the reduced absorptive capacity of the proximal tubule.
- Thiazide diuretics can be prescribed to prevent the excretion of bicarbonates from the body. As they cause volume depletion, the bicarbonate reabsorption in type 2 renal tubular acidosis is enhanced.
- If the underlying cause of proximal renal tubular acidosis is found, it must be corrected.
- Due to decreased proximal phosphate reabsorption and inadequate vitamin D activation, hypophosphatemia is a common finding in proximal renal tubular acidosis. This may give rise to different bone diseases. Therefore, calcium and vitamin D supplements are prescribed to prevent osteomalacia-induced skeletal deformities. These supplements also help to normalise serum phosphate levels.
Treatment of distal or type 1 renal tubular acidosis:
- The aim of treatment is the restoration of the acid-base and electrolyte balance in the body. This helps prevent bone disorders and decreases the buildup of calcium in the kidney. It also helps to avoid the development of kidney stones.
- If the underlying cause of distal renal tubular acidosis is identified, it should be corrected first.
- Medications prescribed for the condition include sodium bicarbonate, potassium citrate, and thiazide diuretics. These medications help correct acidosis. Additionally, sodium bicarbonate helps preserve potassium and calcium in the body.