Abstract: SA-PO0596
Medullary Nephrocalcinosis in Congenital Distal Renal Tubular Acidosis
Session Information
- Fluid, Electrolyte, and Acid-Base Disorders: Case Reports - 2
October 24, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Fluid, Electrolytes, and Acid-Base Disorders
- 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical
Authors
- Bansal, Prachi Tarang, Harbor-UCLA Medical Center, Torrance, California, United States
- Dukkipati, Ramanath B., Harbor-UCLA Medical Center, Torrance, California, United States
- Shah, Anuja P., Harbor-UCLA Medical Center, Torrance, California, United States
Introduction
Distal (type I) renal tubular acidosis (RTA) is caused by impaired hydrogen ion secretion by α-intercalated cells in the collecting duct, resulting in non–anion gap metabolic acidosis, hypokalemia, and inappropriately elevated urine pH (>5.5) despite systemic acidemia. Impaired ammoniagenesis and reduced NH4+ excretion further limit net acid elimination. Chronic urine alkalinity and hypocitraturia promote calcium phosphate supersaturation, predisposing to nephrocalcinosis and nephrolithiasis.
Case Description
A 28-year-old woman with congenital distal RTA presented with hypotension and bleeding. Her home regimen included potassium citrate, sodium citrate, potassium phosphate; she reported nonadherence to spironolactone. On presentation, she was hypotensive and tachycardic. Lab studies demonstrated acute kidney injury, severe hypokalemia (K+ 2.7 mEq/L), and non–anion gap metabolic acidosis (HCO3- 14 mEq/L). Urinalysis revealed an inappropriately elevated urine pH of 8.0. Imaging showed extensive bilateral medullary nephrocalcinosis. We treated with intravenous potassium chloride, continuation of alkali therapy, potassium phosphate supplementation, intravenous fluids, and blood transfusion. Both hypokalemia and metabolic acidosis improved, and she became hemodynamically stable.
Discussion
Nephrocalcinosis occurs in the majority of patients with distal RTA and is driven by sustained alkaline urine, hypocitraturia, and enhanced calcium phosphate precipitation. This case highlights the classic physiologic features of distal RTA, including persistent urine alkalinity despite systemic acidosis, severe hypokalemia, and metabolic acidosis. Hypokalemia is a prominent feature of distal RTA and results from renal potassium wasting, often exacerbated during physiologic stress. Alkali therapy, particularly potassium citrate corrects systemic acidosis, increases urinary citrate excretion, and reduces stone risk, but does not reverse established calcifications. Some patients develop chronic kidney disease due to the progressive nature of the disease.