Quantitative enzymuria following aorto-renal angiography

Quantitative estimation of urinary enzymes has been advocated as a more sensitive marker than conventional renal function tests to assess radio-contrast media induced nephrotoxicity. We studied 27 subjects with normal renal functions who underwent abdominal aortography for varied indications. Among these, 8 also required selective renal arteriography and 3 underwent arch aortography in addition. Sodium iothalamate was used as a radio-contrast medium and the average amount injected was 73 ml (45 to 120 ml) per subject. Standard renal function assessment including urinalysis, 24 hour urinary protein excretion, creatinine clearance done both before and after aortography did not show any significant alteration. Urinary excretion of tubular enzymes including leucine aminopeptidase (LAP), alkaline phosphatase (ALP), gamma-glutamyl transpeptidase (GGT) and maltase (MAL) was estimated before and 2, 24 and 48 hours after aortography. All enzymes showed a significant rise at 2 hours. Urinary excretion of LAP, ALP and GGT peaked at 24 hours after aortography without a further change in MAL levels. Enzymuria returned to baseline values 48 hours following the procedure. It is concluded that an increase in the urinary excretion of the brush-border enzymes within 24 hours of contrast media administration may suggest an early nephrotoxicity.