Abstract: SA-PO0591
A Case of Incomplete Distal Renal Tubular Acidosis (dRTA) Associated with Chronic Lithium Use
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
- Habib, Nazia, Veterans Health Administration Operations, Albany, New York, United States
- Singh, Pratiksha, Albany Medical College, Albany, New York, United States
- Der Mesropian, Paul J., Veterans Health Administration Operations, Albany, New York, United States
Introduction
Learning objectives:
Incomplete dRTA can be associated with lithium use
Importance of identifying incomplete distal RTA in clinical practice
Differentiate complete dRTA from incomplete
Case Description
44-year-old male with medical history significant for hypertension x 15 years and bipolar disorder on lithium therapy for over 15 years was evaluated for elevated serum creatinine (Cr). His only complaint was excessive urination. No history of kidney stones. He developed progressive chronic kidney disease (CKD) over 4 years with baseline serum Cr 1.6-1.8 mg/dL. He had mild intermittent hypokalemia with serum potassium (K) mostly around 3.6 mEq/L. Urine pH was persistently elevated around 6. Urine Ca/Cr was low at 0.02 mg/mg (hypercalciuria >0.2). CKD was likely related to chronic lithium nephrotoxicity. Serum sodium was high-normal around 144 mEq/L and urine specific gravity was lower often less than 1.010, suggesting some ADH resistance related to lithium. Urine K/Cr ratio was elevated at 23 mEq/g indicating renal K loss. Serum bicarbonate was normal at 25 mEq/L with normal AG 11. We suspected incomplete distal RTA (dRTA) given alkaline urine with normal serum bicarbonate, hypokalemia, and likely AVP-resistance (AVP-R). He received KCl 20 mEq/d with normalization of serum K. Lithium was eventually switched to alternative therapy.
Discussion
Incomplete dRTA is a subtler presentation of distal RTA that clinicians should remain attentive to. In contrast to complete dRTA, the acidification defect is partial, characterized by inability to lower urine pH below 5.3-5.5 without hyperchloremic non-anion gap metabolic acidosis. Metabolic acidosis does not occur as there is sufficient acid secretory capacity to handle the daily endogenous acid load of ~1 mEq/kg/day, since the ability to upregulate ammonium excretion remains preserved and the secretory ability of H by type A intercalated cells in the distal nephron is only mildly affected. Lithium inhibits epithelial sodium channel (ENaC)-mediated sodium reabsorption in the cortical collecting duct, reducing the lumen-negative transepithelial voltage that drives H secretion. In partial dRTA, H secretion is partially impaired. This may enhance the electrochemical gradient favoring K secretion resulting in hypokalemia. AVP-R may also be present as in our case. Hypercalciuria with nephrolithiasis can also be seen, however these were absent in our case.