Nephrogenic diabetes insipidus. An unusual presentation of recurrent rectal cancer.

The occurrence of diabetes insipidus (DI) in patients with systemic cancer is caused usually by tumor metastasis to the hypothalamus or posterior pituitary. A 43-year-old man with DI 8 months after radical surgery for a poorly differentiated adenocarcinoma of the distal rectum is reported. A therapeutic trial of intranasal desmopressin acetate did not correct the hyposthenuria, thus localizing the defect to the kidneys. A large tumor recurrence in the pelvis caused bilateral hydroureteronephrosis, resulting in nephrogenic DI. This report shows that not all cases of DI in cancer patients are of central origin.