Snapshot A 36-year-old woman presents to the emergency department with left-sided back pain that radiates to her left groin. Medical history is significant for Sjogren syndrome. On physical exam there is left-sided costovertebral angle tenderness. Laboratory testing is notable for hyperchloremic and normal anion gap metabolic acidosis and hypokalemia. Non-contrast computerized tomography (CT) of the abdomen demonstrates urolithiasis. She is started on ibuprofen and intravenous fluids. Once the calculi passed it was found to be a calcium phosphate stone. (Type I renal tubular acidosis) Introduction Clinical definition renal tubular dysfunction that results in a hyperchloremic and normal anion gap metabolic acidosis there is a relatively normal glomerular filtration rate Renal Tubular Acidosis Type Etiology Pathogenesis Treatment Comments Type II (proximal) Fanconi syndrome Carbonic anhydrase II deficiency Medications acetazolamide ifosfamide topiramate expired tetracyclines Heavy metals e.g., mercury, cadmium, copper, and lead Multiple myeloma Wilson disease ↓ bicarbonate reabsorption in the proximal tubule Potassium citrate Thiazide diuretics Associated with hypokalemia At risk of developing hypophosphatemic rickets Urine pH is initially > 5.5 and then later becomes < 5.5 Type I (distal) Sjogren syndrome Rheumatoid arthritis Anion exchanger gene mutations Medications lithium ifosfamide analgesics amphotericin B Defective hydrogen secretion Sodium bicarbonate or sodium citrate Associated with hypokalemia At risk of developing calcium phosphate stones Urine pH > 5.5 Type IV (hyporeninemic hypoaldosteronism) Diabetic nephropathy Mineralocorticoid deficiency Sickle cell disease Systemic lupus erythematosus Medications heparin angiotensin converting enzyme (ACE) inhibitors angiogensin receptor blockers (ARBs) cyclosporine TMP-SMX potassium sparing diuretics Hyperkalemia results in ↓ ammonia (NH3) synthesis ↓ the capacity to carry acid Treatment depends on the underlying cause Associated with hyperkalemia Urine pH < 5.5