A case of renal salt-wasting syndrome induced by cisplatin and 5-FU during treatment of esophageal squamous cell carcinoma

The combination regimen of cisplatin (CDDP) and fluorouracil (5-FU) (FP) is a standard regimen for definitive chemoradiotherapy, neoadjuvant chemotherapy, and for treatment of unresectable or recurrent esophageal squamous cell carcinoma (ESCC). Here, we report a patient with FP-induced renal salt-wasting syndrome (RSWS) who presented with severe hyponatremia with disturbance of consciousness and was admitted to the intensive care unit (ICU). A 66-year-old man with recurrent ESCC was admitted and started on chemotherapy with FP. From day 3 of the first course of FP, he presented with anorexia and vomiting (grade 3). At day 6, he experienced disturbance of consciousness and blood test showed severe hyponatremia (sodium (Na): 119 mmol/L) accompanied with excessive urinary excretion of Na (181 mmol/L). He was diagnosed with RSWS because of CDDP and was transferred to the ICU. Through intensive monitoring and 3% NaCl infusion, serum Na level and symptoms recovered with no sequelae and he was discharged from the ICU after a 4-day stay. RSWS is sometimes difficult to diagnose because of its low recognition and is misdiagnosed as the syndrome of inappropriate secretion of antidiuretic hormone. During chemotherapy with platinum-based agents, RSWS should be kept in mind as a disorder that causes hyponatremia.