MEASUREMENT OF TOTAL PHOSPHOLIPIDS IN URINE OF PATIENTS TREATED WITH GENTAMICIN

Aims The excretion of phospholipids in urine may be a marker of the ea rly renal toxicity of the aminoglycoside antibiotics. Urinary phosphol ipids are formed in myeloid bodies which develop in the lysosomes of p roximal tubules during treatment with the aminoglycosides, and overflo w into the urine. Methods Published assays were modified in order to m easure the total phospholipid concentrations in human urine. Phospholi pids were extracted from freeze-dried urine samples, digested in conce ntrated sulphuric acid, and the inorganic phosphorus content determine d by complexing with ammonium molybdate and measuring the absorbance a t 820 nm. Ten septicaemic patients treated with gentamicin for 5-7 day s had significantly higher urine phospholipid concentrations than 10 h ealthy untreated control subjects (P<0.0001). There was a negative Lin ear relationship between phospholipid excretion and creatinine clearan ce (r(2) = 0.71). Results In 34 patients with acute pyelonephritis, in creased phospholipid concentrations were observed prior to treatment c ompared with healthy controls (P<0.001) and did not alter during treat ment with gentamicin. However, the phospholipid concentrations decreas ed significantly after treatment was completed (P<0.03). Conclusions T hese studies suggest that urinary phospholipids may indicate early ami noglycoside toxicity but with poor specificity, as many of the infecti ons being treated may themselves be associated with phospholipiduria.