Circadian Variations in Urine Excretion in Chronic Renal Failure

The pattern of urine excretion over 24 hours has been studiedin nineteen patients with stable chronic renal failure of varyingseverity and due to a variety of renal disorders. The patternswere compared with those in eighteen healthy control subjectsof similar age. The 24 hour urine volume was not significantlygreater in the patients (1608 ml ± 112 compared with1710 ml ± 169). A lower urine concentration (341 ±79 mOsm compared with 430 ± 160 mOsm/kg) was associatedwith a lower total 24 hour solute excretion (596 ± 224compared with 699 ± 169 mOsm/24 hours). Frequency ofmicturition, expressed in relation to periods of 24 hours, wassimilar (6.8 ± 0.6 compared with (6.4 ± 0.5).There was an alteration in the normal pattern of urine flow,with more urine at night and less in the day. Nocturia, a consistentfeature of the patients with renal failure is due to reversalof the normal pattern and not to an increased volume of urineor increased frequency of micturition. The time of onset of decreased urine excretion during the daywas associated with the change from recumbency to activity.The morning antidiuresis, and the nocturnal diuresis, are associatedwith, and probably the result of, changes in sodium and totalsolute excretion. The circadian rhythm of potassium excretionremained normal in chronic renal failure, except in very severerenal failure when it was reversed. Alterations in sodium, totalsolute and water excretion were associated with changes in creatinineexcretion and were observed even in mild renal failure. In some patients, studied just before commencing regular dialysis,renal function would have been adequate for reasonable healthhad the rates of excretion observed at night persisted throughoutthe 24 hours. Nocturia, in nineteen patients with chronic renal failure, wasdue to a change in the circadian pattern of urine flow; it issuggested that this results, at least in part, from an inabilityto respond normally to changes from recumbency to activity.