The syndrome of inappropriate secretion of antidiuretic hormone by rectal cancer--a case report.

The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is commonly observed in patients with bronchogenic carcinoma. We report here a rare case of SIADH induced by rectal cancer. Laboratory findings showed that the serum sodium concentration and serum osmolarity were low, and that the ADH level was high. Resection of the rectal cancer resulted in a complete correction of the associated inappropriate ADH. The titer of the rectal cancer tissue proved to be high (80 pg/g).