Lithium nephrotoxicity.

After nearly two decades of concern and controversy surrounding the long-term effects of lithium on the kidney, the fact that lithium is capable of causing a major disturbance in water balance, manifest as polyuria and secondary polydipsia, remains undisputed. A decreased urinary concentrating ability (nephrogenic diabetes insipidus) with a disturbed responsiveness of the distal nephron to the action of ADH (vasopressin) is demonstrable, and the symptoms are largely reversible on cessation of lithium or reduction of the dose. An acute histological lesion of the distal nephron, corresponding to the site of lithium inhibition of the action of ADH, and consisting of epithelial cellular swelling and glycogen deposition, also appears to be readily reversible. Of greater concern is the development of a progressive impairment of urinary concentrating ability in patients on long-term maintenance therapy--especially those with a history of acute lithium toxicity and those additionally treated with neuroleptics. This functional lesion is not always reversible, and the underlying renal histology is a chronic focal interstitial nephropathy. Interestingly, some psychiatric patients never exposed to lithium have demonstrated similar renal histology. There is very little evidence that stable maintenance lithium therapy, without episodes of acute intoxication, is associated with a reduction of glomerular filtration rate. Episodes of acute lithium intoxication are largely predictable, and therefore avoidable, provided appropriate precautions are taken. Patients with polyuria and impaired urinary concentrating ability are at increased risk of acute lithium toxicity because of excessive renal losses of fluid, and these symptoms should be treated in the first instance with dosage reduction.(ABSTRACT TRUNCATED AT 250 WORDS)