Severe polyuria after the resection of adrenal pheochromocytoma

A 73-year-old male patient with hypertension and hyperglycemia was referred to our hospital because of a diagnosis regarding his left adrenal tumor. Because the levels of urinary metanephrine and normetanephrine were elevated, and (131) I-MIBG scintigraphy showed intense uptake in the adrenal tumor, the tumor was diagnosed as a pheochromocytoma. An adrenalectomy was carried out. Severe polyuria, which was accompanied by a rapid decrease in central venous pressure, started 1 hour after the operation. Urine output of more than 8000 mL/day continued until the 16th postoperative day. Plasma antidiuretic hormone (ADH) levels were within the normal range. Plasma human atrial natriuretic peptide (hANP) and brain natriuretic peptide (BNP) were elevated postoperatively, and the elevation of these peptides was one possible cause for the severe polyuria. Because ADH levels in the tumor fluid were not elevated, the tumor was not an ADH-secreting tumor. Urinary β2-microglobulin was significantly elevated after the operation, thus suggesting that renal tubule dysfunction might also have been involved in the polyuria. However, the mechanism of polyuria after the resection of adrenal pheochromocytoma is not fully understood. Polyuria after the resection of adrenal pheochromocytoma is extremely rare, and the present subject is the second case to date.