The pattern of polyuria in relation to duration of lithium treatment

Although in the patient population there was a weak correlation between urine volume and duration of lithium therapy, there was a strong correlation between urine volume and duration of lithium treatment among polyuric patients. This pattern suggests that a subgroup of patients is predisposed to progressive lithium-induced polyuria. It also suggests that the mojority of lithium-treated patients are not predisposed to progressive loss of renal concentrating ability. However, it must be emphasized that prospective studies are required before these suggestions can be accepted since the cross-sectional design of the study cannot test causal hypotheses.