Renal tubular acidosis (RTA) is a group of disorders marked by an impairment in the renal tubules' ability to handle acids. This dysfunction leads to a state of normal anion gap metabolic acidosis (NAGMA) while the renal function remains within the normal parameters.

Type 1 (distal) RTA

Characterized by the renal collecting duct's inability to excrete hydrogen ions, leading to a state of hypokalaemic, hyperchloraemic metabolic acidosis.

Causes

• Autoimmune disorders: Sjögren's, SLE, rheumatoid arthritis
• Drug-induced: analgesic nephropathy, lithium
• Nephrocalcinosis
• Chronic tubulointerstitial nephritis (TIN)

Clinical features

• Hypokalaemic, hyperchloraemic metabolic acidosis
• Rickets/osteomalacia
• Nephrocalcinosis and renal stones

Differential Diagnosis

• Increased urinary pH (>5.3)
• Hypokalaemia
• NAGMA

Management

• Urine alkalinisation with potassium citrate or sodium bicarbonate