Lithium NDI Amiloride — ESENeph MCQ

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HardTubular DisordersLithium NDI AmilorideESENeph

A 40-year-old man presents with serum sodium 148 mmol/L, polyuria (8 L/day), and dilute urine (osmolality 120 mOsm/kg). Desmopressin has no effect on urine concentration. He is on long-term Lithium. What treatment can reduce his polyuria?

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Correct answer: B — Amiloride

Lithium-induced nephrogenic DI does not respond to Desmopressin (the defect is at the collecting duct). Amiloride blocks the ENaC channel through which Lithium enters collecting duct cells, reducing intracellular Lithium accumulation and partially restoring concentrating ability. It is the specific treatment for Lithium-induced NDI. Thiazide diuretics can paradoxically reduce polyuria in DI by causing mild volume depletion and increased proximal reabsorption, but Amiloride is first-line for Lithium NDI.

Reference: Kortenoeven et al 2015 – Amiloride in Lithium NDI; ERA-EDTA Tubular Disorders