Cisplatin-Induced Renal Salt Wasting Syndrome in a Patient with Small Cell Lung Cancer

Platinum-based chemotherapy has been the standard regimen for lung cancer treatment, and cisplatin is the most common platinum compound worldwide. However, its most adverse effect has been nephrotoxicity. Cisplatin-induced renal salt wasting syndrome is a rare type of nephrotoxicity and may result in a rapid decline in serum sodium in only a few days, with or without neurological symptoms and signs. We present the case of a 58-year-old female who was admitted for standard chemotherapy with a cisplatin plus etoposide regimen for her newly diagnosed small cell lung cancer. Prominent weakness, poor appetite and dizziness developed, and an unexpected low serum sodium level (from an initial serum level of 121 mmol/L to 107 mmol/L) was noted on day 3. Her serum sodium level returned to a normal range after saline fluid was administered, and her symptoms recovered shortly afterwards. However, similar episodes developed following the 2nd and 3rd chemotherapy treatments with concurrent cisplatin and etoposide. At that time, we noticed not only a rapid decline of serum sodium but also decreased serum osmolality, increased urine sodium, urine osmolality, and an elevated fractional excretion of sodium (FENa). The clinical course and laboratory data indicated that cisplatin may induce renal salt wasting syndrome. We then replaced the concurrent etoposide and cisplatin regimen with etoposide alone in the 4^(th) and 5^(th) chemotherapy sessions, and no further serum sodium level decrease was noted. We share this report of a rare case and our literature review.