Abnormalities in water homeostasis in small cell anaplastic lung cancer

Forty‐one patients with newly diagnosed small cell anaplastic lung cancer were evaluated for abnormalities in water homeostasis. Each patient underwent a standard water load (SWL) test. Overall, 68% had abnormalities in the SWL test. Abnormalities were found in 47% of the patients with carcinoma clinically limited to one hemithorax and in 86% of the patients with more extensive carcinoma. The determination of urinary antidiuretic hormone levels was available for 27 patients. Abnormally elevated levels were found in 44% of those patients. Forty‐six percent of patients had clinically detectable syndrome of the inappropriate secretion of antidiuretic hormone (SIADH); in 12% of patients water restriction was necessary. The incidence of detectable abnormalities in water homeostasis in this study was higher than has been previously recognized. The SWL test is a sensitive and useful means of determining the presence of impaired water handling in patients with small cell carcinoma of the lung.