A case with renal tubular damage: differentiation of Na reabsorption function by lithium clearance

The recovery of the renal proximal and distal tubular sodium (Na) reabsorption was evaluated by analysis of the physiological metabolism of lithium reabsorbed by the renal tubules in a patient with toxic interstitial nephropathy. Administration of glucocorticoid facilitated the rapid recovery of the proximal tubular Na reabsorption (-0.63 to 3 mmol/min for 2 wk) followed by recovery of phosphate reabsorption (51 to 82% for 2 months). Distal Na reabsorption was not altered for 2 months. Although Li clearance has been previously performed in healthy volunteers, we could differentiate the recovery of the proximal and distal renal tubular function even in a diseased patient.