Navigating the Therapeutic Tightrope: Refractory Lithium-Induced Nephrogenic Diabetes Insipidus in a Patient With Advanced Chronic Kidney Disease

Lithium is the most common and effective mood stabiliser in the management of bipolar disorder. Lithium-induced nephrogenic diabetes insipidus (NDI) is a well-recognised complication of long-term mood stabiliser therapy. However, management becomes exponentially more complex when therapeutic options, such as thiazides or amiloride, are contraindicated due to advanced chronic kidney disease (CKD) or electrolyte instability. We are reporting the case of a man in his 60s with a 40-year history of lithium use who presented with acute-on-chronic kidney injury (AKI) and severe hypernatraemia (164 mmol/L) refractory to standard desmopressin therapy. This case highlights the limitations of conventional NDI treatments in the setting of a low estimated glomerular filtration rate (eGFR) and the necessity of intensive, multidisciplinary care.