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Lithium Nephropathy — ESENeph MCQ

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ModerateTubular DisordersLithium NephropathyESENeph

A 55-year-old man on long-term Lithium for bipolar disorder develops polyuria (4 L/day), polydipsia, and CKD G3b (eGFR 32 mL/min/1.73m2). Renal ultrasound shows small kidneys with microcysts. Urine concentrating ability is impaired (urine osmolality 180 mOsm/kg after water deprivation). What is the diagnosis?

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Correct answer: E — Lithium-induced nephropathy (chronic tubulointerstitial nephritis with nephrogenic DI)

Chronic Lithium use causes tubulointerstitial nephritis with characteristic microcysts and progressive CKD. It also causes nephrogenic diabetes insipidus (resistance to ADH at the collecting duct) leading to polyuria and impaired concentrating ability. Management involves psychiatric review to consider Lithium alternatives, Amiloride (paradoxically reduces polyuria by blocking ENaC through which Lithium enters collecting duct cells), and standard CKD management. Lithium nephrotoxicity is dose- and duration-dependent.

Reference: NICE CG185 2019 – Bipolar Disorder; Markowitz et al 2000 – Lithium Nephropathy