Urinary casts as an indicator of renal tubular damage in patients receiving aminoglycosides

The authors assessed the value of quantitative cast excretion as an early marker of renal tubular damage in 154 seriously ill patients. One hundred twenty-four of these received aminoglycoside antibiotics, and 30 of the 124 experienced a rise in serum creatinine of 0.5 mg/dl or more during therapy. The remaining 30 of the 154 patients were treated with other antibiotics and served as controls. Casts were quantitated in random urines collected before morning diuretic doses. Cast counts in control patients averaged 44±51 casts during the intensive care unit admission. Patients given aminoglycosides without a significant rise in serum creatinine of 0.5 mg/dl or more excreted 153±196 casts, significantly more than controls. In comparison to both the control and nontoxic patients, the 30 nephrotoxic patients excreted significantly more casts (625±364) and were significantly higher as early as 9 days before serum creatinine first rose. Daily urinary cast counts are a rapid and inexpensive means of identifying early renal tubular damage in critically ill patients given aminoglycosides.