[Electrolyte abnormalities associated with cancer: a review].

There are a variety of water and electrolyte disorders in patients with cancer. These disorders occur during the growth of tumors, generally as a consequence of inadequate intake and absorption of electrolytes, renal failure secondary to tumor or rapid tumor destruction and production of metabolically active substances by the tumor. In this paper, the electrolyte abnormalities associated with cancer were reviewed. Hyponatremia is one of the most common clinical electrolyte abnormalities in advanced cancer. Some patients may have hyponatremia, in spite of increased total body sodium and absence of a defect in water diuresis. This status is designated as "sick cell syndrome" or "essential hyponatremia". In addition, the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) in association with various tumors has been described. This syndrome is principally due to water retention, but can also be due to continuous urinary loss of sodium, and hypo-osmolality. Hypercalcemia is associated with coexistent primary hyperparathyroidism, prostaglandin (PGE2) or osteoclast-activating factor. It now seems likely that ectopic PTH is rarely the cause of hypercalcemia in nonparathyroid cancer. There are no data supporting the ectopic production of vitamin D-like substance as an important factor in the hypercalcemia of cancer. There are three general categories in which patients with hypercalcemia and cancer may be placed: those with bone metastases, those without bone metastases of solid tumors and those with hematologic malignancies. Hypokalemia is associated with ectopic ACTH- and insulin--producing tumors, and is often found in patients with mucin-secreting, potassium-losing adenocarcinoma of the colon.